WOT?

[Göran W]

Haven´t seen the topic for a while so:

What´s WOT?

Why WOT?

How WOT?

When WOT?

.... or maybe NO WOT?

I´ve got NS 2000.

[Cadillac Jim]

WOT == Wide Open Throttle. The "WOT process" is using WOT in 2nd gear to go from 40 mph to 60 mph (65 to 100 kmh) and back again, which is said to blow out carbon and pull oil into the piston rings with vacuum. Thus it can help with a car that is rarely driven except at low speeds in traffic.

My opinion is that a better solution is a 500 mile trip at 50 mph or higher, with premium top-tier gasoline. That cleans the carbon out, cleans the injectors, and provides plenty of engine vacuum to bring oil into the piston rings. If you can't do that, then try to do 15 minutes at the speed limit outside of town once a week.

[Göran W]

Hmmmm....... Guess I don´t really need to be concerned? The Eldo runs daily for 2 x 30 km on speed limit 70/100kmh. Passing some trucks and others at 100+. Sometimes at WOT.

[winterset]

My car is too old for WOT. I feel it would put too much pressure on my original 1996 head bolts. Oil consumption is acceptable.

[Texas Jim]

Mine got a few times of WOT yesterday on my 300 mile trip...

Passing cars on two lane roads....

Stand on it at 60/65, it downshifts to 2nd... by the time you clear the first car, it has upshifted to 3rd at 88mph and if there are 2 cars you are passing, by the time you clear the 2nd one you are well over 100 MPH...

[rockfangd]

My car is too old for WOT. I feel it would put too much pressure on my original 1996 head bolts. Oil consumption is acceptable.

I beg to differ on that one. I drive my 96 hard. even with over 200k it loves it. The harder I drive it the better it runs. They are made for abuse. I think it keeps them running good

[Cadillac Jim]

The head bolts aren't weak. When they pull out, it's because there is some problem with the integrity of the threads, usually because traces of coolant that has gone acid have gotten past the sealing in the bolt hole wells. Keep your coolant changed and drive the car any way you want.

I'll agree that the WOT treatment is hard on an engine, particularly using engine braking at high RPM, which is done to pull oil into the rings to help un-stick them. But decelerating at high RPM maximizes rotational forces on the pistons and is really not recommended for any engine. I wouldn't do it over 4500 RPM; I would up-shift instead.

[KHE]

The head bolts aren't weak. When they pull out, it's because there is some problem with the integrity of the threads, usually because traces of coolant that has gone acid have gotten past the sealing in the bolt hole wells. Keep your coolant changed and drive the car any way you want.

I'll agree that the WOT treatment is hard on an engine, particularly using engine braking at high RPM, which is done to pull oil into the rings to help un-stick them. But decelerating at high RPM maximizes rotational forces on the pistons and is really not recommended for any engine. I wouldn't do it over 4500 RPM; I would up-shift instead.

The engne breaking causes the pistons rings to rotate which frees them up - it is not oil pulled into the rings. Oil may be pulled into the rings but it is not the oil that causes the rings to "unstick".

[Texas Jim]

I reckon mine is still ok at almost 140,000 miles...and it gets very frequent WOT... LOL LOL

I change the oil when the OLM gets to about 30 percent, which is usually about 8000 miles... it will be about a half quart low at that time.

And that half quart usage usually occurs between the 40 percent and the 30 percent range of the OLM.

That's why I change it at 30 percent.or if it has been several months, like it is now, I will change it.

It was last changed in September and it is now at 33 percent and a half quart low.

I plan on changing it this coming week.

[winterset]

I like using the oil consumption to my advantage. I have not been driving the car much, so oil consumption is a good thing. Adding a quart every 800 miles or so keeps the crankcase fresh between changes. Yes jim, its the engine braking that i'm afraid of. Even though the coolant was changes 3x in its lifetime, and bars is added, i am weary of those too fine headbolt threads pulling out. Also, i keep it 1/2 quart low to minimize a gummy intake from pcv blowby.

Oil formulation has changed, and oil burning is no longer a death sentence for the cat like it was back in the '80's and 90's

Besides, it may be carbon deposits that end up plugging any potential breaches in head gasket seals.

[rockfangd]

lol you never know. I run mine 7.5 all the time. people say it has to be 8 only because they dont know everything

[Texas Jim]

lol you never know. I run mine 7.5 all the time. people say it has to be 8 only because they dont know everything

I can't swear how much it takes to fill mine up because it has always been changed at the dealer with full synthetic.

I know it is right on the full mark when ever I get it changed and it STAYS there till it has around 5000 miles on it, then it will slowly drop and usually reaches about a half quart low over the next 2000 to 3000 miles....

Then I get the oil changed and we start the process all over again... LOL

[Cadillac Jim]

Hmmmm....... Guess I don´t really need to be concerned? The Eldo runs daily for 2 x 30 km on speed limit 70/100kmh. Passing some trucks and others at 100+. Sometimes at WOT.

That sounds like enough exercise to keep things limbered up OK. The "WOT treatment" was recommended a long time ago as a way to loosen up stuck rings. It's a DIY answer to

#PI00606A: 4.6L LD8, L37 Engines Oil Consumption Greater than 1 Qt. in 2,000 Miles - cylinder economy - (Aug 13, 2003) and the similar #01-06-01-011,

which, ruling out conditions vanishingly rare in Northstars, recommends a procedure in

#02-06-01-009C: Higher Than Expected Oil Consumption (Clean Piston Rings) - (Oct 23, 2003).

The procedure involves pulling the plugs in a hot engine and placing special solvent in each cylinder (Piston and Ring Cleaner, P/N 12378549 (in Canada, P/N 88901334), included in kit P/N 12378545 (in Canada, P/N 88901333)), leaving it for at least two hours and not more than three, then sucking it out of the cylinders. A special tool (canister, J 35800-A) is used for the solvent, and it is pressurized to 15 psi to use. The dirty solvent is aspirated from the cylinders using another special tool (evacuation pump assembly, J 45076-2) which is used with shop air.

This is similar to the older carbon-removal process but uses a different solvent. This ring-clearing treatment also removes carbon, though.

I can imagine the labor involved in removing all eight plugs from a hot engine, then putting measured dollops of special solvent into each cylinder, then using an oven timer, then using the air-powered suction pump to suck it out of each cylinder. Numbers 1, 3 and 7 on the back bank are particularly painful to contemplate.

Interesting warning about this process:

Important: The piston and ring cleaner solution must remain in the cylinder for a minimum of two hours. If the solution is removed in less than two hours, the cleaning process will not be 100% effective and may not correct the condition. Additionally, do not allow the cleaning solution to remain in the engine more than three hours. If the dissolved solution is left in the cylinders more than three hours, it will soak back into the rings and cause the rings to stick again.

Just another time-critical issue when slaving over the back cylinders of a hot engine, and a challenge to techs about reading the whole TSB. I had mine done in 2002 and the tech left the solution in for 4.5 hours.

Interestingly enough, the years of applicability are 1996 through 2002, with just 2003 Devilles "Prior to 3U213641" and 2003 Sevilles "Prior to 3U215818" so not all Northstars are likely to need treatment for stuck rings.

Another interesting point is that there is a new piston ring part number for 1996-1999 (P/N 89017431, 8 required) and for 2000-2003 (P/N89017413, 8 required). So, if the dealer decides to replace the rings because the snake oil treatment didn't work, they have a different design on the piston rings.

There are a couple of things that stand out that show engine build mistakes that can cause oil burning. In the ring cleaning TSB:

Be sure to install the second compression ring notch side down.

A longer warning in PI00606A:

Special Note: The cylinder walls should inspected for any damage. The cylinder walls do not require any surface conditioning. (no honing necessary). Also the 2nd ring should be installed with the notch side down in the cylinder bore and finally, be sure to use the reduced cylinder head bolt torques when reassembling the 96 -99 4.6L (LD8/L37) engine

From the 2002 FSM, to look for to diagnose excessive oil consumption:

• Piston and rings improperly installed or miss-fitted to the cylinder bore

Interesting things that PI00606A says to check for in engines still in warranty:

• Check for missing/upside-down rings
• Check for possible ring end gap alignment.

From the 2002 FSM on the section on installing piston rings:

• Space the oil control piston ring end gaps (1, 2) a minimum of 90 degrees apart.
• Once the rings are installed, set the ring gaps for the oil control, second and top rings in the positions shown:

  9.1. Oil control ring expander and second compression ring gaps position 1.

  9.2. Upper oil control ring gap position 2.

  9.3. Top compression ring gap position 3.

  9.4. Lower oil control ring gap position 4.

In service, piston rings move in the piston grooves but they aren't supposed to rotate significantly. If they do rotate so that the ring gaps align, or even come close to aligning, you will have problems with oil burning and/or compression.

[KHE]

lol you never know. I run mine 7.5 all the time. people say it has to be 8 only because they dont know everything

The capacity of the sump is 7.5 quarts. Those who say 8 need to read the owner's manual. Anything over 7.5 quarts will be burned up quickly anyway.

[Göran W]

I´ve never experianced stuck rings......

[Cadillac Jim]

lol you never know. I run mine 7.5 all the time. people say it has to be 8 only because they dont know everything

The 2002 FSM says that it is safe to run the car until the "CHECK OIL LEVEL" warning appears, because it still has 5 quarts left. Just avoid a lot of 1 G high-speed braking and long curves and such, or if you do that, watch the oil light.