Quote:
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.
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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