I Asked About My Oil Dilemma At Bob the Oil Guy. - A40 Is the best?

[Erik]

After stupidly not stocking up on oil. And finding myself in a bind as I need some quick, I decided to also ask the oil gurus at Bob Is The Oil Guy their thoughts on the best oil for an LT5. No, there aren?t any LT5 experts there, but they sure seem to know their oils. The consensus, after a lot of posts already, is a Porsche spec, A40 oil. Even the Mobil 1 European spec A40 oil has 1100ppm of zinc, and seems readily available.

They have jumped into to the discussion with enthusiasm, to say the least. I?m happy with the AMSOIL in the long term, but it is interesting to read about other oil options.

Here is the link, if you dare:

https://bobistheoilguy.com/forums/threads/what-is-plan-b-if-i-cant-get-amsoil-z-rod-for-my-1990-corvette-zr-1.356668/

[1991 Corvette ZR-1]

Oil for the engine and the transmission on these ZR-1s are discussions that can go on until the end of time. It is nice to see the discussion though. I try not to lose sleep over it. You can tie yourself in knots following recommendations, counter recommendations and counters to those counters. Personally, I stick to Mobil 1 10W-30. It has worked very well for me.

[Matt B]

Oil for the engine and the transmission on these ZR-1s are discussions that can go on until the end of time.

...which in fact holds true for ALL cars. Let's assume electric vehicles were developed to ultimately end those discussions [emoji6]

[Erik]

Oil for the engine and the transmission on these ZR-1s are discussions that can go on until the end of time. It is nice to see the discussion though. I try not to lose sleep over it. You can tie yourself in knots following recommendations, counter recommendations and counters to those counters. Personally, I stick to Mobil 1 10W-30. It has worked very well for me.

I was home alone and bored. Wife working the late shift, so the mind starts to wonder. I don't think I've been over at BTOG in more then 5 years. And it's just for that reason. I don't think too much of my oil choices, just grab one that I like and be done with it.

But, it is interesting to see where technology is, and it does seem that A40 is a pretty impressive oil.

I was just roaming around Wal- Mart the other day, and thought I'd check the pricing on Mobil 1 10W30. I was shocked to find that there was no 10W30 of any kind to be found.

[Erik]

...which in fact holds true for ALL cars. Let's assume electric vehicles were developed to ultimately end those discussions [emoji6]

Nah, they will find something else to fight about. :)

[Erik]

If nothing else, I have learned something new. I didn't realize that Zinc was something that was used up as you drove. I figured it was just there and stayed at the same number as long as it was in there. Nope!

Theoretically, if we wanted to be completely anal, shouldn't we be adding a little extra zinc every thousand miles or so?

[Erik]

Through all of that education, I did find an oil that seems to work in a pinch with the LT5. Mobil 1 FS 0W-40. 1100 ppm zinc, independently verified. Plus the bonus of being dirt cheap at Walmart.

[Erik]

And right from Mobil.

[Hib Halverson]

Contrary to the opinion of many, 1G LT5s do not require high amounts of ZDDP because, while they are flat tappet engines, they are not pushrod engines, thus their valve spring tension is less than is required by an OHV engine which has to control not only the valve, retainer, locks and lifter but also the mass of a pushrod and part of the rocker arm mass. If valve springs have less tension, there is less need for the extreme pressure lubricants in ZDDP. Less ZDDP means longer cat converter life. IG LT5s can do fine with 800 or so PPM ZDDP but many of the engine oils ZRoners tend to buy (ie: Amzoil, some blends of Mobil 1, Driven and Red Line) are about 1000-1200 PPM.

If I still had my C4 ZR1 today, I'd use a 0W40 oil, either Red Line 0W40, Driven DI40 (also a 0W40) or, in a pinch, Mobil 1 0W40 ESV.

The reason I would have used a 0W40 over the 10W30 I used I had kept "Barney" my Purple '95 is that 1) oil technology advances, just like many other things and 2) the main advantage of a 0W vs a 5W or a 10W on a cold start is the 0W gets to the bearings and valve gear quicker than does a 5W or a 10W. A large proportion of engine wear occurs during cold starts in the time between when the rotating assembly starts to move and when oil pressure has built to the nominal level. I'm not making that up, either. When GM went to 0W40 in all Corvette engines for 2019, part of why that happened was research GM did on how quickly oil pressure built in various parts of Gen 5 V8s showed there was a clear durability advantage in a 0W oil over a 5W or 10W during cold starts.

Today I use 0W40 in the LS6 in our C5 ZO6, in the LSA7 in our C6 ZO6 and the 2G LT5 in our C7 ZR1.

For those who still prefer M1 10W30, but best prices I've seen on it is at Costco.