The Guru's oil consumption writeup up close

[winterset]

Once again, i re-read the infamous post the Guru made many years ago. I carefully looked at the statement he made about overfilling the crankcase. I always just read the part about checking oil when it is hot. Then i read where he said that you should not fill the oil to the top of the fill mark, but rather just put enough oil in where the level falls right in the middle of the cross hatches on the stick. I have been doing that too. I suspect overfilling to the top also causes blowby, and the oil gets sucked into the intake, burns, and the burned oil is better at causing carbon deposits on the rings - A kind of self reinforcing feedback.

[Cadillac Jim]

It's always better to keep the oil a little farther from the crankshaft. And, the Northstar holds 7 quarts for a 4.6 liter lightly-loaded (automotive) engine, a capacity sufficient for a truck that does long, sustained loading of the engine. So, backing off a pint is likely to be a little better for lessening the slinging about of the oil.

[winterset]

While we are on the subject of oil level. if someone can let me know next time they change their oil. After the oil s drained, Turn the key to just the run position, and let me know if the "check oil level" message appears. I am not sure if the car needs to running for the car to detect a low oil message. I think checking that this function works is important. I do not think mine is working properly, so i am always checking the level every 500 miles or so. I'd rather wait for the message.

[airmike]

I would rather NOT wait for the message, because if it decided to fail today, you would not know if that happened and then you would be waiting on something that isn't going to happen. The message would be great to let you know of a sudden loss of oil that you wouldn't usually be checking for though. I think it was intended for non mechanically minded people, probably the stereotypical blonde wife/girlfriend.

[BodybyFisher]

Winterset, I recall the Guru stating that the Northstar could operate just fine on 5 quarts of oil, the reason for the additional oil was to keep the oil pickup covered during high G turns. When I changed my oil, I added enough oil to just cover the little nub at the end of the dipstick. Keeping the oil lower helps limit oil leaking from the case half if your engine suffers from leaking.

This is going to be voluminous but, I think it is good to post the Guru's thoughts on Oil Consumption, WOT procedure, cross hatch, oil checking and oil level, babying it verses "driving it like you stole it", variability between engines in the manufacturing process, and other excellent points. A word of caution: we have modified the WOT Procedure from what the Guru presents it here, many of us were skiddish taking the RPM up to 6200 for an L37 and 6000 for an LD8 in an aging engine. Here are posts by the Guru that I collected over the years:

Northstar Oil Consumption

"It is not unusual for a Northstar to use more oil than some other engines. It is a high performance engine and has to allow a little more oil to the top rings for lube as as well as down the 32 valve guides.

Design intent for oil consumption would put the engine at about 4000 miles per quart consumption but due to the variables in production parameters there are engines that will use 1 quart per 1000-1500 miles.... perfectly normal and acceptable... but more oil consumption than "intended". Nothing will be wrong with the engine but the continuous oil adds are aggravating. If this is the case then understand that the engine is probably going to run a long long time like that as the cylinder walls , rings, valve guides, etc. like all that oil that you are putting in and the continuous oil adds fortify the used oil in the sump and replenish the additive package in the oil that is slowly depleted under normal usage.

Comparing the 4.9 to the Northstar is an apples to oranges deal. The 4.9 is an excellent engine for it's purpose but does not offer nearly the performance, durability, fuel economy and emission control capability of the Northstar. The Northstar is a high output engine and likes to be "used".

The best way to minimize oil consumption in a Northstar is to keep the sump filled slightly low (many are continuously overfilled) by only checking the oil level when hot and only filling the sump with 7 quarts of oil (7.5 with a dry filter at a change.) A typical 8 quart fill at a change is "required" to put the oil level on the full mark when cold but is actually overfilling the crankcase promoting oil consumption.

Use conventional mineral oil (synthetic is not required at all) as it tends to provide better oil consumption.

An last, but not least, air the engine out frequently. It likes to be used and red-line upshifts at WOT help promote clean combustion chambers, exercise the piston rings to keep them free of carbon buildup and keep them mobile and to ensure the engine is broken in and maximum sealing is obtained. The Northstar does not like to be babied around. It likes to be run hard frequently with a WOT blast in merging or whatever.... Even engines reported to use 1 quart per 1500 miles tend to improve to 2500 miles per quart or better when subjected to a regular schedule of use and "abuse"...

------------------------------------------------------------------------------------------------------------------------------------------------

The subject of oil consumption really does not have a "final" answer. The fact is that there is some variability in oil consumption in all production engines.... regardless of who makes them on which continent. All the manufacturers recognize this and virtually all of them will call oil consumption as great as 1 quart in 1000 miles "normal" "acceptable" "allowable" "within production tolerances" etc... This doesn't mean that all engines will get 1000 MPQ or that the engine was designed to get 1000 MPQ...it just recognizes the fact that there are going to be some engines that get 1000 MPQ that will be perfectly fine upon disassembly and will have nothing "wrong" with them.

The variables that usually enter into oil consumption are primarily associated with the piston/ring/cylinder bore. The number of valves or type of valve actuation has little to do with it.

The single biggest variable and the one that has been discussed at great length on this forum is the cylinder bore finish or the cylinder honing pattern. The higher performance the engine is the more attention must be paid to the honing pattern and retention of oil on the cylinder walls to lubricate the piston and rings at full load , high RPM operation. The Northstar engine uses a very aggressive cylinder bore finish that tends to retain a lot of oil to protect the piston and rings. When the blocks are honed at the factory there is a tolerance in the bore finish due to the fact that the honing stones will wear and need replacement. A brand new stone gives a slightly more aggressive pattern than a "used" stone....so a block honed with new stones will have a more aggressive finish and most likely will use more oil.

Another variable is bore roundness. Like it or not, the bores tend to "move" slightly as the engine heats up and cools down and bolt tensions relax, etc. over time. All this contributes to slight bore out of roundness that is not bad or good...just different.

Carbon buildup in the rings and ring sealing are also variables that come into play with break in, operating schedule, type of oil used, etc.

The one thing that I can attest to is that many, many customer oil consumption complaint engines have been torn down with absolutely nothing wrong found. The engines are often reassembled and put into test cars and driven by the engineers and more often than not the high oil consumption does not repeat itself !!! The single biggest common cause seems to be breakin...or lack there of. Many, many oil consuming NOrthstar engines are "fixed" by some full throttle operation. I often joke about "driving it like you stole it" but it really is no joke. The Northstar engine was designed as a high performance engine to be run hard and fast. Those that are run hard typically exhibit excellent ring seal, little carbon build up and good oil economy. We have seen engines with tens of thousands of miles on them that the rings have not sealed or mated to the sides of the ring grooves because the operating schedule was so light duty. The moral here is to flog it .... often.

In any case, the nice thing about the engines with the more aggressive honing pattern is that the pistons, rings and bores will last forever. It is very common to tear down a 200,000 mile Northstar engine and still see the original honing pattern in the cylinders. There is never any sign of cylinder wall wear and the idea of a wear "ridge" at the top of the cylinder bore is something that is laughable on a Northstar.

The other nice thing about a little oil consumption is that it adds tremendous safety factor to the oil change interval. Nothing could be better for the engine than an occasional quart of fresh oil. You can take the worst oil on the market and add a fresh quart every 1000 miles and over the life of the engine the wear will be better than an engine run on the best oil with no adds between changes.

While no one in the engineering community wants high oil consumption the fact is that there is some variability in the oil consumption of an engine manufactured at the rate of 1200 per day. The specs of what is "normal" simply reflects this...it does not imply that all engines would get this or that something is wrong with and engine that gets more or less oil consumption.

There have been a lot of engineering changes over the years on the Northstar aimed at reducing the overall oil consumption and reducing the variability in the oil consumption of different engines. Many changes have been made to the honing process to make it more consistent. Changes to the piston and ring groove treatment have been made to make it more resistant to wear, pound out and micro welding at low oil retention rates. Regardless, there is still some variability.

One other thing that affects oil consumption, or the customers perception of oil consumption, is the move toward longer and longer change intervals. With the allowable change interval reaching as high as 12,500 miles on a 2003 Northstar if the oil life monitor is followed this could mean the addition of 3,4 or 5 quarts of oil to a very healthy engine. If the owner changes their oil every 2000 or 3000 miles, despite the oil life monitor recommendations, then they would not have to add any oil between changes. The oil consumption is the same....the amount added between changes is all that is different. Yet, many customers do not make the distinction. Field surveyors repeatedly show that "acceptable" oil consumption means "not having to add between changes"...whatever MPQ that is...???

The issue of oil consumption is very emotional , too, as many people perceive higher oil consumption as 'poor quality" or an indication that something is wrong. Blue smoke, fouling plugs, noise, etc...is a sign of something wrong. Using 1 quart in 1000 miles might be perfectly normal for an engine that has the high limit "rough" hone finish and is perfectly in spec...yet it will be perceived differently.

The Northstar engine in particular was designed to be a high performance engine and to perform well at high speeds and high loads. The engines are tested at loads and speeds for time periods few customers will ever be able to duplicate. It is unfortunate that the engineering that goes into making the engine capable of such running sometimes contributes to more oil consumption... especially as the production machining tolerances are taken into account.

The items mentioned about overfilling also apply. Make sure that the system is not overfilled as any excess oil will be pushed out the PCV. The best bet is to always check the oil hot and keep it midway between the add and full mark. Don't always top off and don't top off cold to the full mark as that will overfill the sump.

Hope this helps rather than adding more fuel to the fire... so to speak.

Incidentally, there is a lot in the message board / forum archives... check using "oil consumption" and read up. Always keep in mind that for every "oil burner" you read about on the internet there are 10,000 or more driving around perfectly fine that the people are not posting about... You are always going to read about the horror cases on the internet".

--------------------------------------------------------------------------

Occasional Full-Throttle Acceleration Is Good For Your Engine

There are many advantages to occasional full throttle accelerations with a Northstar and any engine.

It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.

Occasional WOT accelerations also help seat the rings to the ring lands and exercise the rings and keep them mobile and from becoming stuck in carbon in the ring lands. At high RPM and WOT the rings move around on the piston - they actually rotate on the piston and will polish away any carbon and seat themselves to the sides of the ring grooves. This is especially important on the 2000 and later Northstars which had hard anodized top ring lands on the pistons. Very hard and wear resistant - also harder to break-in and seat the rings to the sides of the ring-lands to promote the best possible seal. Many oil consumption complaints on the 2000 and later engines are related, to some extent, with the rings never seating to the sides of the ring-grooves due to lack of load as the engine was babied around forever. Even engines with rings stuck in the ring-grooves due to carbon build up can eventually be freed up with enough high RPM operation.

WOTs warm up the engine thoroughly and clean out the exhaust due to temperature in the exhaust and high flow rates blasting particles, rust and such out of the system.

Frequent WOT operation will not hurt the engine or the transmission. They're designed for that. The healthiest engines that I have seen at high miles are always the ones that are run the hardest. Rings are free on the pistons and sealing; no carbon buildup.

The exercise that I think works best for many things is to select manual 2nd gear on an isolated stretch of expressway. This takes the transmission shifting out of the question if you are worried about hurting it. Start at 55 MPH or so and go to WOT in 2nd gear and hold it until the RPM reaches near the normal shift point - i.e. 6500 for an L37 and 6000 for an LD8. Hold the throttle wide open until the engine reaches, say, 6200 for an STS and then just let completely off the throttle. Leave the transmission in 2nd so that the engine brakes the car and creates some pretty heavy over-run conditions at high vacuum levels. Let it slow until it is about 55 or so and then go to WOT again and repeat. This exercise really loads the rings, allows variable RPM operation at WOT for several seconds continuously, creates heavy over-run which tends to unload the rings and make them move and thus exercise them in the ring grooves and it will blow-out carbon and the exhaust - all without creating a spectical of yourself and attracting the attention of cops. You can do it on most any freeway and stay within the 70-75 MPH range allowable. Once a week like this will keep the engine cleaned out and healthy and is DEFINITELY recommended for the Northstar in particular.

The Northstar engine was designed/developed/validated to be run hard. It was expected that people would use the performance of the engine - which few people seem to do. The biggest single problem that many issues stem from is lack of use at full throttle by the owners. It just doesn't like to be babied around. The rings are low-tension by design for good high RPM operating characteristics and low friction/good power. They work best if "used" and kept free.

In every conversation with owners I have had, once the owner started doing the WOTs and using the power of the engine they report no more carbon rap, better oil economy, no "smoke" when they do light it up (keep the exhaust cleaned out. If you notice a "cloud" at WOT then you are not doing enough WOTs...) etc... A bit of judicious use of the other end of the throttle travel is a GOOD thing...

______________________________________________________________________

Here is one more of the GURU's posts regarding FLAT TAPPET LIFTERS and ZDDP, and his RECOMMENDED oil and additive (EOS). Note his statement that he uses 15W40 Rotella or Delvac and "flat tappets can take all of the anti-wear additive you can throw at them! Beginning in 2000 the Northstar began using roller cam followers.

NO WHERE do you see the GURU stating to use 5W30 in the Flat Tappet version of the Northstar, no where!

[Terje Treff]

1. My 99`STS has enormous oil consumption! At least a quart pr. 100 miles (!) I have only seen oil sweat in the engine bay, and no drip anywhere.
2. It seems to "collect" oil and blow it out occasionally. Either at close to WOT, but also at moderate throttle if I have been stuck in traffic for a while. When it blows it out the smoke cloud can be enormous and quite embarrasing. The color is bluish.
3. I don`t generally see any smoke during driving, only on the occasions when it decides to blow it out in huge plumes.
4. The engine runs GREAT! Strong, smooth, powerful! Only occasional misfire with a short squeak sound that I assume is because of oil in the cylinders.
5. I recently bought the car so I don`t know the service history or what type of oil used. I have been topping off with 5W-30 dino oil for the time being. It has 137,000 miles.
6. I have tried repeated WOT applications many, many times. It made no difference so far.
7. If traffic allows, and I can drive generally "agressive", it appears to not collect as much oil to blow out. In other words it seems to "collect" oil in particular when driving calmly, either highway driving or stop and go traffic (i.e. the problem is the same if I go 70mph on highway or 5mph in traffic, as long as I don`t use heavy throttle). I have been staying in 3rd for long periods of time at 50-70mph and it doesn`t appear to make much difference (gas mileage suffers greatly though).
8. It also blows a huge plume when I start the engine after the car has been sitting - no matter how long, half our or 3 days.

I have read all the comments about this problem, but wanted to know if there is a particular place I should start, considering that the oil consumption is extreme. Am I wasting my time with WOT applications ? Should I use oil additives or fuel additives ? Or does this seem to be a severe enough problem that the only way to fix it is to replace piston rings ? How do I check the PVC valve? Where is it ? I have lots of experience working on cars (hobby) but this is an unkown car to me.

I would really appreciate any advice. The car is in beautiful condition inside and out with only minor other problems. I love it, but this is taking the fun out of it. I would be super happy filling a quart pr. 1000 miles....

[BodybyFisher]

It is not just a matter of doing WOTs, you must do the WOT procedure, have you donenthe WOT Procedure? You must do the procedure as described above to exercise the rings. If you have not done it, do it at least once a week.

What oil do you use?, dino or synthetic and what viscosity? STOP topping off with 5W30, you take 10W30, and if you use synthetic stop immediately.

How high do you keep the oil on the stick?

Is the bottom of the engine wet?

How many miles on engine?

[KHE]

1. My 99`STS has enormous oil consumption! At least a quart pr. 100 miles (!) I have only seen oil sweat in the engine bay, and no drip anywhere.
2. It seems to "collect" oil and blow it out occasionally. Either at close to WOT, but also at moderate throttle if I have been stuck in traffic for a while. When it blows it out the smoke cloud can be enormous and quite embarrasing. The color is bluish.
3. I don`t generally see any smoke during driving, only on the occasions when it decides to blow it out in huge plumes.
4. The engine runs GREAT! Strong, smooth, powerful! Only occasional misfire with a short squeak sound that I assume is because of oil in the cylinders.
5. I recently bought the car so I don`t know the service history or what type of oil used. I have been topping off with 5W-30 dino oil for the time being. It has 137,000 miles.
6. I have tried repeated WOT applications many, many times. It made no difference so far.
7. If traffic allows, and I can drive generally "agressive", it appears to not collect as much oil to blow out. In other words it seems to "collect" oil in particular when driving calmly, either highway driving or stop and go traffic (i.e. the problem is the same if I go 70mph on highway or 5mph in traffic, as long as I don`t use heavy throttle). I have been staying in 3rd for long periods of time at 50-70mph and it doesn`t appear to make much difference (gas mileage suffers greatly though).
8. It also blows a huge plume when I start the engine after the car has been sitting - no matter how long, half our or 3 days.

I have read all the comments about this problem, but wanted to know if there is a particular place I should start, considering that the oil consumption is extreme. Am I wasting my time with WOT applications ? Should I use oil additives or fuel additives ? Or does this seem to be a severe enough problem that the only way to fix it is to replace piston rings ? How do I check the PVC valve? Where is it ? I have lots of experience working on cars (hobby) but this is an unkown car to me.

I would really appreciate any advice. The car is in beautiful condition inside and out with only minor other problems. I love it, but this is taking the fun out of it. I would be super happy filling a quart pr. 1000 miles....

I think the correct oil for your car is 10W-30 but take a look in the owner's manual and/or check the oil fill cap to be sure.

Blue smoke = burning oil. Your oil control rings may be stuck. The deep carbon cleaning procedure may be needed. With the engine cold, remove the spark plugs and fill the cylinders with GM top engine cleaner. It then needs to sit - the longer, the better - to dissolve the crud that is around the rings. Use a Mityvac to suck as much fluid out of the cylinders as possible, then unplug the ignition control module and crank the engine over to expel any excess solvent. Wipe up any solvent, then change the engine oil.

Reconnect the ignition control module and start the engine - drive the car hard - it will really smoke. Run it until the engine reaches operating temp., then change the engine oil and filter again. This procedure along with WOT's should free up the rings.

[cdgrinci]

Since you've tried the 'Italian Tuneup' and have gained no-joy, I would believe that your next place to look is your valve train bushings/bearings and valve train guides.

[BodybyFisher]

Big T your next job is to follow KHEs advice, above with the UEC.

It appears you have NOT done the proper WOT procedure yet. You MUST do the WOT procedure properly because decelerating hard in 2nd gear exercises the rings (after doing what KHE said) and the deceleration creates negative backpressure in the combustion chambers that sucks crap out of the exhaust ports.

Try this to see if it helps and do the WOT procedure once a week for a month. Simple WOTs will not help

[Cadillac Jim]

The 2003 TSB on oil burning and stuck rings:

http://jameskbeard.com/jameskbeard/Cadillac_Files/02-06-01-009C_Oil_Consumption.pdf

I would work on the stuck rings a bit more before I started looking at worn-out mechanical parts in the head.

I had that problem at one time, suddenly but thoroughly, and fixed it by changing where I had the car serviced, making sure that I had the oil that I thought I had when the oil was changed.

[Terje Treff]

Ok, there`s some good advice. It is definitely possible I have not done the WOT procedure correctly and I will double check that. And I did fill it up to the max on the dip stick, which I will no longer do.

I don`t know what oil is in the car, because I bought it recently, but I have been topping off with 5W-30 dino oil for the most part. I`m not sure I see the big difference between using 5W30 or 10W30, but I am not an oil expert.

I looked under the car when I bought it and did not see any oil sweat there, but I have seen a little in the engine bay. But it certainly isn`t enough that it drips down anywhere. It`s just oil sweat.

The car has 137,000 miles.

Is the GM top engine cleaner only available at GM dealers, or is something equivalent available at the car parts stores ?

My concern was that since the oil consumption is so extreme, that some of these procedures might be a waste of time. But on the other hand I figured if there was something seriously wrong with the engine it wouldn`t run as strong and smooth as it does (?). I have to fill several quarts on one tank of gas.

[Terje Treff]

Seems to be varying thoughts on dino vs. synthetic. Some people her do NOT use synthetic, and others say DO use it.

I am European, and you can`t even buy dino oil anymore over there. Everyone uses synthetic on everything. Clearly there are benefits to the synthetic oil, cleaning properties and better ability to retain the oil film on extreme ends of the temperature range ?

[BodybyFisher]

10W30 is what the engine is specd and validated for, look on your filler cap if you need confirmation.

As far as synthetic.....and I do NOT want to make this an oil thread, but, AGAIN the engine was designed based on dino 10w30s flow characteristics to maintain proper oil pressure throughout the engine, meaning the lifter bore clearances of which there are 32, were specd based on dino oils flow characteristics and since synthetic flows 7 times better than dino, there is a danger of dropping the oil pressure, especially at the top of the engine. Especially at idle when the oil pressure is low. And especially as the engine ages and the clearances widen

The engine was not specd for synthetic, beginning in 2000 all of those 32 lifters or 32 potential leak points were eliminated as they introduced roller cams and synthetic was specd.

I am in the process of doing extensive oil pressure testing to prove this point on the 93 to 99 NSs

[BodybyFisher]

The GM UEC is available from the dealer maybe amazon, do not use a so called equivalent, ie seafoam AGAIN, you are TRYING to solve a problem, NO? And we are trying to belp, why debate everything? Lets try to get the intended results WITHOUT reinventing the wheel

KHE posted a procedure developed by GM to solve the caked up oil ring problem and excessive oil consumption, exactly what you have! It has worked, why modify a proven process and change a variable on your own corrupting the intended result?

I don't know about anyone else here but I am not smarter than GM, the guru or proven results.

I do know one thing when I bought my 96 it SUCKED OIL and it was owned by an oldman who babied it, after a few WOT procedures oil consumption was never an issue, during thr 70K miles I owned it

[Terje Treff]

The GM UEC is available from the dealer maybe amazon, do not use a so called equivalent, ie seafoam AGAIN, you are TRYING to solve a problem, NO? And we are trying to belp, why debate everything? Lets try to get the intended results WITHOUT reinventing the wheel

KHE posted a procedure developed by GM to solve the caked up oil ring problem and excessive oil consumption, exactly what you have! It has worked, why modify a proven process?

That sounds good. I will more forward in this direction. It`s such a great car, so I really want to get this fixed. I will update as we go along.

[winterset]

Have you checked both pcv valves? If one is fouled up, i think it will cause blowby and cause oil to get sucked into the intake. I am only 90% sure we have 2. Shake them and clean it out with carb cleaner till you hear the check valve rattle loudly when you shake it.

Long periods of overfillng also clogs up the pcv.

[Terje Treff]

Have you checked both pcv valves? If one is fouled up, i think it will cause blowby and cause oil to get sucked into the intake. I am only 90% sure we have 2. Shake them and clean it out with carb cleaner till you hear the check valve rattle loudly when you shake it.

Long periods of overfillng also clogs up the pcv.

Ok,I`ll have to find them and check them. Pointers on where they are located ?

[BodybyFisher]

Let us know how this turns out.

From my experience there is only one PCV valve and its in the rear cam cover near the ICM, the front cam cover has a breather that connects to the throttle body that completes the PCV circuit. That is from a 96 manual, and I know the 98 is the same as I just ripped one down.

[KHE]

Seems to be varying thoughts on dino vs. synthetic. Some people her do NOT use synthetic, and others say DO use it.

I am European, and you can`t even buy dino oil anymore over there. Everyone uses synthetic on everything. Clearly there are benefits to the synthetic oil, cleaning properties and better ability to retain the oil film on extreme ends of the temperature range ?

Using synthetic oil won't hurt anything but it is completely unnecessary in these engines. If you can't get regular oil, then use Mobil 1 10W-30 or equivalent.

The engine was not specd for synthetic, beginning in 2000 all of those 32 lifters or 32 potential leak points were eliminated as they introduced roller cams and synthetic was specd.

Even the 2000+ Northstars did not require synthetic. Maybe 2006 and later but my 2005 does not specify synthetic.

[BodybyFisher]

Thanks Kevin, good clarification,it doesnt require synthetic.

I believe the 93 through 99 can be harmed by synthetic after 2 years of research. I will have empirical data that will either prove or disprove my opinion and that harm has nothing to do with zddp or accelerated wear.

[Cadillac Jim]

The PCV valve (just one) on the 1997 is on the rear cam cover on the far right side on the top. There is a right-angle vacuum hose fitting for it that sometimes can get soft and quack like a duck or collapse when there has been too much oil through it for too long. The PCV valve fits into a grommet in the cam cover.

[Terje Treff]

Thank you guys, I will work on checking these things going forward and report my findings.

[Terje Treff]

Thanks Kevin, good clarification,it doesnt require synthetic.

I believe the 93 through 99 can be harmed by synthetic after 2 years of research. I will have empirical data that will either prove or disprove my opinion and that harm has nothing to do with zddp or accelerated wear.

I am not an engineer or mechanic, but I have worked as a service advisor for several years. In my country, Norway, like most european countries, we use synthetic on everything, old or new. Never heard of damage due to synthetic oil. Generally non-synthetic isn`t even available at shops. I would be very surprised if your findings indicate damage due to the use of synthetic oil. I would go so far as to say if your research does indicate damage as a result of synthetic oil, the experiment is flawed (issues listed below notwithstanding).

I know some engines are not "engineered" for synthetic oil.

I know some older engines can develop leaks with synthetic.

I know some older engines can even experience internal damage due to synthetic oil loosening deposits.

However, these issues are not indicators that synthetic oil is harmful to certain engines, in my opinion. They are issues that arise from circumstantial factors.

I`m not trying to re-open an argument that I am sure has been hashed out many times here and other similar boards. I only have one point: synthetic is used on everything in Europe, old or new, and I have never heard of any cases of engine damage as a result. This is a discussion I ever only seen in the USA. There cannot be any doubt that synthetic oil is generally better than "dino" oil ?

[Terje Treff]

Thanks Kevin, good clarification,it doesnt require synthetic.

I believe the 93 through 99 can be harmed by synthetic after 2 years of research. I will have empirical data that will either prove or disprove my opinion and that harm has nothing to do with zddp or accelerated wear.

I am not an engineer or mechanic, but I have worked as a service advisor for several years. In my country, Norway, like most european countries, we use synthetic on everything, old or new. Never heard of damage due to synthetic oil. Generally non-synthetic isn`t even available at shops. I would be very surprised if your findings indicate damage due to the use of synthetic oil. I would go so far as to say if your research does indicate damage as a result of synthetic oil, the experiment is flawed (issues listed below notwithstanding).

I know some engines are not "engineered" for synthetic oil.

I know some older engines can develop leaks with synthetic.

I know some older engines can even experience internal damage due to synthetic oil loosening deposits.

However, these issues are not indicators that synthetic oil is harmful to certain engines, in my opinion. They are issues that arise from circumstantial factors.

I`m not trying to re-open an argument that I am sure has been hashed out many times here and other similar boards. I only have one point: synthetic is used on everything in Europe, old or new, and I have never heard of any cases of engine damage as a result. This is a discussion I ever only seen in the USA. There cannot be any doubt that synthetic oil is generally better than "dino" oil ?

....I would even claim that if these engines were run with synthetic from the start, they would not experience stuck oil rings nearly as often.