oil change question

[Hog]

Originally Posted by soslow

A few days ago I brought my 1990 ZR-1 in for an oil change and specified to the mechanic that I wanted Mobil 1 High Mileage oil. He replaced the 8.5 quarts and gave me a half quart to bring home. When I got home, I noticed that he put in 5w-30 weight oil instead of the 10W-30 that the car calls for. Is this a big deal? It is synthetic and has some 10W-30 from the last oil remaining that doesn't drain out. Any thoughts?
The car only has 11,000 miles on it.

The 5W30 will have the exact same viscosity at 100ºC/212ºF as the 10W30 oil will. The difference will be during cold start temperatures, where the 5W30 oil will flow easier than the 10W30 will. Your engine may in fact have a decrease in cold start wear as the 5W oil will flow easier at that lower cold start temperature.
Since it sounds as though you have the luxury of being able to drive your Z in the Winter(I envy you) simply start up the Beast and drive it. IMO No need to warm up an EFI car, nothing gets you engine up to operating temperature faster than gently driving it. Having it sit there and idle merely prolongs the amount of time that elapses before your engine reaches operating temperatures. Very little wear occurs during normal driving, most of it occurs during cold starts.

OEMs have been decreasing the cold temperature viscosity numbers over the years. In the 90's it was 10W, then went down to a thinner 5W**, and now is down to a 0W for many OEMs.

IMO In regards to the LT5. I feel that its more important to provide an engine oil that has the proper high pressure lubricants package for the lobe followers/lifter, chains and the large chain guide surface area(as well as other areas)as there are not a roller type, than worry about the cold(Winter) viscosity number of an engine oil, esp. a synthetic oil. The synthetic oils that some people use have much better cold flow properties than conventional oils do.
And at the other end of the spectrum temperature wise, synthetics are superior in terms of high thermal stability. This would be of great concern IMO in an early car with OEM turbocharging such as the Callaway Corvettes rpo B2K. Though they didn't use flat tappets, they did have rocker arms that exhibit galling above 6000rpm(not an issue in OEM parameters).

Of course all of my opines here excuse non of the issues that you should have with the oil change business that provided you with an incorrect fill.

[Hib Halverson]

For 1990-1992, the factory fill oil for an LT5 engine was a 10W30 petroleum-based oil (not synthetic) and Mobil Oil was the supplier.

For 1993-1995 the factory fill in an LT5 was a 5W30 synthetic "Mobil 1".

A 5W30 synthetic can be used in the early engine with no ill effects.

In fact, you don't even need M1 "High Milage" because the LT5, by virtue of its OHC valve train, doesn't require additional ZDDP.

If I still owned my ZR-1 what would I put in it? Gibbs Driven LS30 which is a 5W30 with a more advanced base stock than any of the Mobil 1 products use.

For frequent track use, I'd go with Gibbs Driven DT40 a 5W40 which uses the same mPAO base stock.

[Paul Workman]

Thanks, Hib for "turning the page". The "m" in "mPAO" is a proprietary process developed by ExxonMobil, marketed under the "Driven" banner, ,if I'm not mistaken.

I think all would agree that testimonials are far from scientific evidence - mine included. And, too (oil) suppliers' marketing hype is also suspect - perhaps the worst, in some cases.

http://www.deluxeoil.com/royal_purple_claims.htm

It would sure be refreshing to see independent test comparisons of leading brands (beit Amsoil or whatever) that are conducted in such a way as to be clearly understood by laymen. (I'd like to see how the mPAO compares to leading brands; tests done in a way the LT5 - in particular - could be demonstrated. (Considerations for timing chain lengths, cam sprocket loading, rpm, etc.)

And, too... There's "the BEST" and then there's "GOOD ENOUGH" to be considered. I haven't seen a test that is specific to the LT5's unique criteria to make a "good enough" determination. But, regardless of what I or any of us is aware of, is not exceeding the "good enough" product with one providing an extra margin for error a good thing - especially considering the cost to repair the LT5?

Looking forward to the next independent, comprehensive analysis including the "Driven" products alongside of other top brands.

[Dynomite]

Most guys reading all this now do not know what to do

You guys make it soooooo complicated. I shall make it simple

[Paul Workman]

Originally Posted by Dynomite

Most guys reading all this now do not know what to do

You guys make it soooooo complicated. I shall make it simple

Ockham's razor...

[scottskill]

I would recommend AMSOIL Z-ROD 10W-30.

[Hog]

Originally Posted by Hib Halverson

For 1990-1992, the factory fill oil for an LT5 engine was a 10W30 petroleum-based oil (not synthetic) and Mobil Oil was the supplier.

For 1993-1995 the factory fill in an LT5 was a 5W30 synthetic "Mobil 1".

A 5W30 synthetic can be used in the early engine with no ill effects.

In fact, you don't even need M1 "High Milage" because the LT5, by virtue of its OHC valve train, doesn't require additional ZDDP.

If I still owned my ZR-1 what would I put in it? Gibbs Driven LS30 which is a 5W30 with a more advanced base stock than any of the Mobil 1 products use.

For frequent track use, I'd go with Gibbs Driven DT40 a 5W40 which uses the same mPAO base stock.

You make a great point about the DOHC architecture. Seeing that it doesn't use the "cam lobe/lifter force multipliers" aka in a 1.5:1 ratio that most GEN 1 and GEN 2 pushrod SBC's used (except 96-97 LT4 which used the 1.6:1 ratio) less force exerted by the LT5 OEM valvesprings don't require the pressures that the pushrod engines did.

On average though, most oils have in fact reduced the amount of ZDDP contained within since the GEN 1 and GEN 2 LT5's were designed built (all done by MY1993).
The entire Mobil One lineup ranges from 800ppm for the Extended line, around a 1000-1300 for most of the rest of the M1 line(depending on viscosity. With their race only Mobil 1 Racing with 1850ppm.

Extra Zinc depends upon the oil referenced, formulations from the early 90's are different than 2016.

I would love to see a 100,000mile 1992 engine run on its OEM conventional spec oil and a 1993 GEN2 LT5 its OEM synthetic spec oil with 100,000miles on it, both disassembled and compared.

Question: Would the area between the flat tappet and cam lobe, be the area of highest of contact pressure inside the LT5?
I know that the Zinc in oils is useful as a high pressure lubricant.
As always, thanks for your input Hib.

And yes, the other Paul, I agree that testimonials are far from scientific, no matter who is giving them.

Edit: Here are the Mobil 1 specs (current as of Feb 2016) that I was roughly referencing.
https://mobiloil.com/~/media/amer/us...guide-2016.pdf