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When Should I Start Using High Mileage Oil


Texas Jim

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A couple thoughts come to mind.

1. How long does your engine run at 6000 RPM?

2. An occasional dose of WOT is beneficial to the Northstar and recommended.

3. When the Northstar was being tested it was run at WOT for 300 hours (12.5 days) straight. Now remember, it was spec'd for conventional 10W30 so that's what it was tested on. That should dispel any worries about it thinning out or breaking down.

4. I seriously doubt that the oil ever gets to 300 degrees. Conventional oil will not survive at those temps. That is why you get a change oil message if you overheat the engine and that comes on at about 260 or 265. The engine has an oil cooler which passes engine oil through a heat exchanger in the radiator side tank.

5. While Bob is the oil guy is a good site with lots of info, keep in mind two things. 1. Those guys are fanatics. They have oil in their veins and get a transfusion every three months. 2. I believe that site is sponsored by oil additive manufacturers.

Even though mine was spec'd for 5W30 I still use 10W30. Either one should serve you well.

While I agree with most of your comments, I will take exception to the Oil temperatures. I have been in vehicles with oil temperature gauges and sure enough it does get that high.

Coolant temp doesn't measure the actual instantaneous Oil temp at the bearing surfaces, or Oil temp on the Cylinder walls [inside the Engine Cylinder during Power Stroke combustion cycle can be over 1500F]. Oil is used to help cool the engine as well as lubricate.

In some Formula One racing applications ,18000 RPM use, Oil [typically 50 or 60W] will be preheated before the race and temp controlled at over 220F . I have friends who do short track and drag racing [i'm in NC Nascar country] and Racing type oil is a one time [day] use fluid.

And Yes, all sites are sponsored and certainly all oil makers claim they are the best. Caddy Info board discussions are useful to get data and experience from actual users. I tend to be over-conservative on oil, coolant etc, since these are the 'easy' things to do to maintain a vehicle. My rule of thumb is to use something if it is clearly better AND cost effective. Hence my quest for an Equal to or better than Mobil One equivalent at a lower cost. Mobil One has always over priced their product IMO.

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The 1997 FSM says specifically *not* to use heavier weight oils such as 20W-40. I wouldn't use any oil with the second number other than 30 in a Northstar, any year, unless the owner's manual says it's OK to do so.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I have not read any of this thread, but I am SO glad I have stayed away from it, :lol:

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Not to worry BBF. Hard as it may be to believe, it has remained civil and informative. No oil wars have erupted (as intended).

Mobil One has always over priced their product IMO.

I'll drink to that.

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The 1997 FSM says specifically *not* to use heavier weight oils such as 20W-40. I wouldn't use any oil with the second number other than 30 in a Northstar, any year, unless the owner's manual says it's OK to do so.

The guru said it was perfectly OK to use the 15W-40 Rotella/Delo/Delvac diesel oils in the older Northstars without roller cam followers. I use Rotella 10W-30 in my '97 STS and my Fleetwood Brougham.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The guru is good enough for me.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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The 1997 FSM says specifically *not* to use heavier weight oils such as 20W-40. I wouldn't use any oil with the second number other than 30 in a Northstar, any year, unless the owner's manual says it's OK to do so.

The guru said it was perfectly OK to use the 15W-40 Rotella/Delo/Delvac diesel oils in the older Northstars without roller cam followers. I use Rotella 10W-30 in my '97 STS and my Fleetwood Brougham.

Thanks for the info. this is some the feedback I was hoping to hear. Did it also apply to 2000+ N* or was there a Viscosity concern with later N* designs?

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You could probably use it in a 2000+, but the concern was for the flat tappet rubbing element lifters in the pre 2000's.

Thanks for your experience . I will be trying the Rotella Synth. 5W-40 in my 03 DHS as a trial.

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I have not read any of this thread, but I am SO glad I have stayed away from it, :lol:

I'll try to keep myself out of it too. :D

By the way, the manual says not to use heavy-weight oil such as 20W-50

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Just use a 10W30 high milage oil (I won't tell the brand) but you prob. know what I mean.....

109,000 and still going STRONG.....Mobile 1 5W30 is for the gov. mandated MPG.....

Oil these days is about 100% better then "back in the day" oils......

OK i'll tell the brand............. Valvoline Max life 10W30.... lot cheaper then Mobile 1 ..Ha..

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5W30 is for the gov. mandated MPG.....

Yup, tree hugger oil. I still use 10W30.

laugh.gifThis made me laugh!

big4870885.jpg

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One source for good info on Oils is "Bob is the Oil Guy" site.

My preference is manufactured synthetic oil [most any brand] since it is more uniform and has fewer contaminants than refined "dino" oil and typically will perform better with less breakdown in High RPM use. My 04XLR 4.6 Northstar specs Mobil 1 Synthetic so I know that the Caddy engineers proved out this one in performance applications. In my 03 DHS I use Synthetic 5W-30 as well as the rest of my vehicles with no problems. My family drives over 100K per year [ 2 Adults, 2 teenagers] and I get to be the full time mechanic on our 5 vehicles.

Since your car is running fine with no leaks, etc. I would keep away for High mileage oils with additional additives [ contaminants?].

The engine oil recommended for your Cadillac engine is Mobil 1 OR the equivalent synthetic oil, of which there are many. Mobil 1 isn't the only oil that can be used in that engine.

Cadillac uses Mobil 1 as the factory fill oil because Exxon/Mobil has the factory fill contract with General Motors, so when Cadillac wants a synthetic oil of course they use the synthetic oil they are already contracted to use.

PAO Group IV synthetic oils have no contaminants in them whatsoever, but the Group III, "synthetic oils", (which are derived from petroleum crude oil), still have some contaminants in them, as crude oils have all manner of contaminants present in them such as napthenes, benzyenes, asphalts, waxes, sulfurs, etc., etc. So even with an unopened bottle of petroleum crude oil based oil there are already contaminants in this oil being poured into your engine mixing with blowby contaminants and creating other corrosive acids inside that expensive engine.

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It's quite simple really. Stick to the specs and you will be sure that no harm is done. Be aware though that older Northstars require higher ZDDP levels than the oils of today can deliver.

On the other hand using synthetic oils on a car that doesn't demand it won't hurt anything, BUT there will be no magical earnings/positive effects from using synthetics because the only advantage in using synthetic is a slightly higher temperature breakdown resistance.

If I may, true synthetic oils offer many advantages to old school dead dinosaur/petroleum oils. 1. Improved fuel economy/lower emissions. 2. An internally cleaner engine. 3. Easier cold/winter engine starts. 4. Longer engine life. 5. Reduced maintenance costs. 6. Cooler engine temperatures. 7. Superior high temperature engine protection and many other advantages as well.

For more information on this commonly misunderstood topic, read the excellent article below -

"SYNTHETIC OIL: Rx for Long Engine Life" -- My link

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The higher heat breakdown temperature and lower sludge susceptibility of synthetic oil may translate to less likelihood of sticking rings in cars that are driven lightly 100% of the time.

Seems like the only REAL reason to use the synthetics. My STS runs on semi-synthetic 5W-30 but that is because I can't get my hands on a dino-oil with that viscosity (I drive quite hard).

If I lived in the US then I would be happy to use synthetic oils but over here the price is twice as much for synthetic versus dino-oils.

Buyer beware; "semi-synthetic" oils can have as little as 1% synthetic oil in them and still be called a, "semi-synthetic".

A good synthetic oil is many times much cheaper to use/lower cost than an old school dead dinosaur/petroleum oil. Price is one thing, but cost is another.

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If memory servers, MadeinAmerica is an Amsoil dealer or wholesaler. Note attribution of GM's recommendation of Mobil 1 to "the factory fill contract." I would wager that GM powertrain engineers would be part of the decision process in making any such contract, should it exist (and I have absolutely no reason to believe that any contract exists that would bind any day-to-day decisions at engine plants), and they could have made such contract, or the dealers could make recommendations for, say, Havoline (which was the standard GM recommendation in the 1960's, I believe), Pennzoil, Quaker State, or Amsoil. I see no mention of any oil brand in my owner's manual or 1997 FSM, only oil grades and weights. My dealers would put in any oil that I asked them to, although the warranty requires that the oil be 10W-30, 5W-30, or 0W-30, and if the dealer can't get it they may ask you to bring it.

I haven't done in-depth checking in a couple of years now, but as far as I can determine the best synthetic oils in the 5W-30 grade are Mobil 1 and Amsoil.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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If memory servers, MadeinAmerica is an Amsoil dealer or wholesaler. Note attribution of GM's recommendation of Mobil 1 to "the factory fill contract." I would wager that GM powertrain engineers would be part of the decision process in making any such contract, should it exist (and I have absolutely no reason to believe that any contract exists that would bind any day-to-day decisions at engine plants), and they could have made such contract, or the dealers could make recommendations for, say, Havoline (which was the standard GM recommendation in the 1960's, I believe), Pennzoil, Quaker State, or Amsoil. I see no mention of any oil brand in my owner's manual or 1997 FSM, only oil grades and weights. My dealers would put in any oil that I asked them to, although the warranty requires that the oil be 10W-30, 5W-30, or 0W-30, and if the dealer can't get it they may ask you to bring it.

I haven't done in-depth checking in a couple of years now, but as far as I can determine the best synthetic oils in the 5W-30 grade are Mobil 1 and Amsoil.

[/quote

I have been an AMSOIL synthetic lubricants dealer for the past 25 years, yes, but that doesn't change the fact that Exxon/Mobil has the factory fill contract for General Motors and this is the reason that when GM uses a synthetic oil in their vehicles the oil chosen is Mobil 1 synthetic.

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I did point out that, if there is a fill contract or any other contract with an oil supplier for a GM factory, or if they routinely order oil from any particular supplier, or if they recommend any particular oil, then it is because GM decided to seek such a contract, order for such a supplier, or to recommend such a supplier. GM or any other customer of any product does business with whomever they choose.

Ergo, to say that they fill new engines *because* there is such a contract is reverse logic, that GM must use Mobil 1 because there is a fill contract. This begs the question of, who decided to engage in any such contract? Why, it seems to me that the deciding entity must be GM, with participation and inputs form GM powertrain teams, would you not say?

I think that Amsoil would be considered by GM as a fill oil, if they requested to bid or supply fill oil at GM factories, their price and service was competitive, and GM audits of their capabilities revealed that there was no way that Amsoil supply limitations could starve GM factories of needed supplies. One such requirement might be that the fill oil be available to the general public for use in GM cars by owners at competitive prices, which is a problem for Amsoil. This may be a chicken-and-egg problem, because Amsoil's higher prices and more limited availability may be due to their smaller size as a company. One way to get a jump start on that situation, if indeed it is a consideration, is to get the fill contract on a smaller manufacturer's cars that gets Amsoil better visibility. I suggest Ferrarri, or perhaps high-end Porsche sports cars, or other highly regarded cars with smaller production volumes.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Synthetic oil was not spec's for my engine or any of the Northstars in question in this thread. They were designed, tested and spec'd for conventional motor oil.

Engines are not designed to use certain types of oil or not. Engines are designed for oils meeting set performance criteria. In this regard, oil is oil, but synthetic oils do everything a petroleum oil does, they just do it better. :)

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I did point out that, if there is a fill contract or any other contract with an oil supplier for a GM factory, or if they routinely order oil from any particular supplier, or if they recommend any particular oil, then it is because GM decided to seek such a contract, order for such a supplier, or to recommend such a supplier. GM or any other customer of any product does business with whomever they choose.

Ergo, to say that they fill new engines *because* there is such a contract is reverse logic, that GM must use Mobil 1 because there is a fill contract. This begs the question of, who decided to engage in any such contract? Why, it seems to me that the deciding entity must be GM, with participation and inputs form GM powertrain teams, would you not say?

I think that Amsoil would be considered by GM as a fill oil, if they requested to bid or supply fill oil at GM factories, their price and service was competitive, and GM audits of their capabilities revealed that there was no way that Amsoil supply limitations could starve GM factories of needed supplies. One such requirement might be that the fill oil be available to the general public for use in GM cars by owners at competitive prices, which is a problem for Amsoil. This may be a chicken-and-egg problem, because Amsoil's higher prices and more limited availability may be due to their smaller size as a company. One way to get a jump start on that situation, if indeed it is a consideration, is to get the fill contract on a smaller manufacturer's cars that gets Amsoil better visibility. I suggest Ferrarri, or perhaps high-end Porsche sports cars, or other highly regarded cars with smaller production volumes.

AMSOIL synthetic motor oils sell as low as only $4.20 per quart, so price isn't a concern. Factory fill oils have to meet performance criteria set by the API, i.e. API SM, or SN oils, not the brand of the oil.

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Synthetic oil was not spec's for my engine or any of the Northstars in question in this thread. They were designed, tested and spec'd for conventional motor oil.

Engines are not designed to use certain types of oil or not. Engines are designed for oils meeting set performance criteria. In this regard, oil is oil, but synthetic oils do everything a petroleum oil does, they just do it better. :)

That pretty much says it all. The end result (except cost) is the same no matter which you use.

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