interesting article oil from GM

[Clem Z.]

[Lyndon S.]

Re: interesting article oil from GM

Even so what about the shear factor? The diesel engine oils have got to be better on just that alone. Well I am sticking with the diesel oil in my older cars. Cant wait to hear what Duke says.

Kelly

[Clem Z.]

Re: interesting article oil from GM

the only people that reported trouble were the ones that installed after market camshafts.

[Alan Drake]

Re: interesting article oil from GM

I first heard about the oil issue many years ago relative to Buick Grand Nationals getting their STOCK V6's trashed due to the oil so it's not just the after market stuff. The difference in cost for C? oil is nothing so I'll just continue to use it, OH need it anyways for truck.

[Kevin M.]

Re: interesting article oil from GM

I always felt it couldn't hurt only help.

Kevin

[Ken B.]

Re: interesting article oil from GM

Clem...I have been told by numerous people about the use of synthetic oil in a new motor. I have been told that the rings and other parts do not seat properly.I was going to use a synthetic but after hearing of this i chose not to. One person that i consider very knowledgable said that GM has a service bulletin that says do not use it until you get 2500 miles on the motor..Any truth to that..Synthetic is my choice so any help that you can give will be awesome..

[Terry M.]

Re: interesting article oil from GM

For years (since sometime in the C-4 era), including current production, Corvettes have been factory filled with Mobil 1 synthetic. There are no widespread reports of rings failing to seat. I would call this an "old wife's tale" except I have never heard an old wife pass it on.

[Duke W.]

Re: interesting article oil from GM

I'm not sure if there are any significant differences in the shear stability and oxidation tests for S and C categories. Modern base stocks for both are very good, today, and have improved significantly over time.

I have no major disagreement with the article, but offer the following comments.

SM oils are "okay" for vintage engines, but if a better alternative is available at about the same price, why not use it?

S-category oils with winter grades of 10W or less are limited to .08% phosphorous, which places a limit on ZDDP. The current C-category specification, CJ-4, limits P to .12%, which is about the level of previous oils, many of which were dual rated, carrying both the then current S and C service categories.

As stated in the article the motivation for reduction of ZDDP (as measured by P) is protection of catalysts, and modern engines don't need as much because of fewer sliding elements in valvetrains.

It's a matter of chosing "okay" or "better" motor oil for vintage engines. I also use CJ-4 in my two "near vintage" daily drivers both of which have "modern" three way catalysts. One has a direct acting DOHC valvetrain, the other is SOHC with shaft mounted non-roller rocker arms. Since they both have low mileage for their age and only accumulate about a thousand miles a year, each, I'm not concerned about catalyst poisoning with CJ-4, and they both perform well in field emission tests.

Duke

[John H.]

Re: interesting article oil from GM

The Viper factory fill is also Mobil 1, and we built the engine from the bare block up in the assembly plant, right next to the Chassis Line where we installed it. Modern moly-faced piston rings seat in about five minutes after first-fire.

[Joe L.]

Re: interesting article oil from GM

Terry and Ken-----

LT1 small blocks for the 1992 model year were the first to be factory-filled with synthetic motor oil. The LT5 went to it in 1993 or 1994. Since then, I believe that all Corvette engines have been factory filled with Mobil 1.

[Paul L.]

Re: interesting article oil from GM

John,
I just bought a new Impala 3.5L (120 miles on odometer now). Are you saying I can switch to Mobil 1 at the first oil change? I plan to change oil at 1,000 miles.

[Ken B.]

Re: interesting article oil from GM

Joe..So as i understand....my 75 that has a new rebuild will be just fine with a synthetic oil?

[Dick W.]

Re: interesting article oil from GM

Just be aware that some of the sealing technologies used on the vintage engines probably will not keep synthetic from leaking. Synthetic seems to invent new places to leak.

[Terry M.]

Ken & Paul

You both can use synthetic oil in your new engines whenever you choose. Many miles of big smiles to you both.

[Joe L.]

Re: interesting article oil from GM

Ken-----

Yup, just fine. And, if you choose to use the dual-rated, diesel/gasoline rated oils, you can get those in synthetic, too.