Hey! I recently bought a 93 Z28 and i am busy bringing her up to code. Its time for an oil change, but i dont know which oil to use. The engine has 239K on the motor so i am guessing i'll need a thicker oil. I was thinking about using a single grade like a sae30 or sae40, but wanted to hear from you all.

I live in California and we dont have any extreme winters so cold starting shouldnt be a problem.

 

I'd use any decent 10W-40 dino stuff. My own brand of choice is Kendall GT1. But I can't say that is based on real assumption of superiority. It's just that I have used it for years without a problem.

http://www.kendallmotoroil.com/NR/rd..._GT1_HP_MO.pdf

Rich

 

10w30 sounds good then. Thanks!

 

What Rich said.

 

I will third the 10w-40 recommendation.

The second number is the key one brand 10w-30 can and often is thinner than anothers 0w-30.
Analysis has pretty well shown even lower milage LT1s prefer thick 30wt. to low 40wt. anyway.

 

Okay so i am confused now. do i want 10w-30 or 10w-40 ?

 

10W-40.

Rich

 

By the way...

Don't automatically assume that a high mileage engine needs thicker oil. It's true they often do, but if the engine has been properly cared for it's not an issue.

You may have to take a guess the first time, in which case the old standbys like 10w-30 are a good place to start. Then look at your oil pressure gauge and see how you're doing. You want at least 10lbs per 1000 rpm.

One thing...
I've done a lot of research on this subject and one of the interesting things that came up was that when dealing with Dino oil, it's not good to go with anything over a 20-point spread, because it's basically being done with the additives, not the oil. So for instance, 10w-30 is good, but 10w-40 is getting a bit wide. 15w-40 is borderline. Basically, once you go above a 20 point spread, go to a synthetic.


Now look...
I use synthetic, but the bottom line is that if you use a quality dino like Quaker State or any of the other name brand; and change your oil on schedule, you'll be fine.

If you do go to a synthetic, there are many quality brands, with Mobil1 being the most recognizable and not even particularly pricey anymore.

I personally use Amsoil but I use their high-end stuff with extended changes and oil analysis.


The bottom line though is that you want to do three basic things:
1) Regimented oil changes, and do them on time.
2) A quality name brand of oil, whether you go Dino or Synth.
3) Sufficient weight to get you at least 10lbs/1000rpm.


I want to finish by telling you a story regarding oil weight and why I began doing my research.

A while back I owned a 1993 VR6 Passat.

As a traditionalist, I automatically began using 20w-50 Mobil One to protect my engine at the high speeds I like to drive.

I noticed that in traffic my engine temps went alarmingly high, even to the point where the computer would shut off my air conditioning.

On a suggestion from another owner, I switched to a lighter weight oil. I eventually ended up using 10w30 in the summer, 5w-30 in the fall & spring, and 0w-30 in the winter.

I noticed a DRAMATIC drop in engine temps in traffic. I'm talking about 20-30 degrees. I also began getting TWO MPG better mileage. Yes, I said TWO.
Finally, I could FEEL the difference in power in the seat of my pants.


I realize that this goes against the conventional wisdom of thicker oils for performance engine, not to mention the high volume oil pumps we hot-rodders like to use; but it turns out that we old timers were wrong.

Or at least wrong about modern engine with their tighter tolerances.

 

Analysis has proven the LT1 to perfer thick 30wts to low 40wts. Amsoil tends thich and I think you are grossly overcomplicating thins using different weight different times of year if sticking with Amsoil I would probably just stick with the 5w-30 or 0w-30 year round.
Older 10w-40 was bad as the additives used to make it do that would break down and sludge up but oil today is of signifigantly better quality.

 

I have a 1994 z28...105,000miles...I use AMSOIL 5w30 100% synthetic...no issues.

I'm not saying one is better than the other...just stating what I use and it has not been a problem for me. My car still runs like it's new...that's why I still use it.

 

Thanks for the great advice you all, but it seems so much more complicated. My motor runs great.. even at its higher mileage. I'll give 10w-30 a try and see how the engine likes it.. I am not sure i know how to ensure that the engine is getting 10lbs per 1000 rpm.. can someone shed some light on that one?

 

as far as synthetic mobil1 goes what do you guys recommend the 10-40? or 10-30 cause i know that they run thinner usually

 

mobil 1 synthetic oil tends to run a little thinner. if you are going to use mobil 1 syn, go with the 10w40.

 

I have not seen M1 in 10w-40 but the 0w-40 and 5w-40 are good choices for the LT1. If going with Amsoil the 0w-30 5w-30 or 10w-30 are good choices.

 

i know it sounds stupid but is one better then the other ? (mobil vs. amsoil) or is it just preference thank you for the weight comparisons thats exactly what i was confused on cleared that up for me