I've seen a few threads about it in the past few months. Actually it seemed to be what WalMart was pushing in the Mobil-1 jugs around here, I had to look in a different WalMart to find my normal 5w30.

Anyway, a friend of mine who is a master ASE technician told me to always use the oil (weight) that the car was designed to be used with, so I've been sticking with 5w30, and maybe some 10w30 in the summer time...always mobil-1. Just wondering what the verdict is out there on 15w50. I've seen the gimmick before where someone advertises a "high horsepower engine motor oil" and puts a picture of a camaro on it, but I've read on tech boards that whatever weight it was that was being advertised (years ago) was way to thick for the engine. I kinda figured 15w50 to be much like that.

So in conclusion, what makes 15w50 so good? Is it better than 5w30? I live in New Jersey, so the coldest it gets in the winter is about 0 degrees and the hottest it gets in the summer is about 102.

 

15w50 is too thick. It's more for racing applications where cold starts are not an issue and where their clearances are looser and need the thicker oil.

If you run 15w50 in your street driven car, you're just losing horsepower and MPG and not getting any better protection for your engine.

In my experiences, the LT1 prefers an oil with a viscosity of between 12-14cst at 100c, so it likes a very thick 30wt to a low 40wt oil. So this means something like Redline 5w30 or 10w30, Amsoil 5w30 or 10w30, German Castrol 0w30, Mobil 1 0w40, etc. You can look at an oil's spec sheets to see their viscosity at 100c.

 

Yeah that's what I thought. I had seen some people on here mentioning that they were using it, but I thought it was too thick. Thanks for the clarification, Patman.

 

I would love to see oil analysis results on 15w50 in an LT1 if anyone is up to getting it done by the way.

It doesn't cost that much (about $20) and can be very informative. Blackstone Labs does a good job, so does Wearcheck USA.

 

? for anyone. Is the Mobil 1 0w40, which is a 'european' formula, made in Germany along with the Castrol 0w30?

 

when i got my car the guy used mobil 1 20-50
will it hurt for me too change?
anything i should do if i do change?

 

If your talking about the Mobile-1 Fully Synthetic Highperformance 15W-50 buy it..it's awsome

Put it in my engine...car totally loved it. Wouldn't use anything Else.

 

No, the Mobil 1 0w40 is made here in the US, but from what I've heard, it's the identical formula to the 0w40 Mobil 1 sold around the world. They call it the European formula mainly because it passes a lot of the tests required by European cars.

 

Thanks Patman. I trust the european tests are a little tougher to pass.

 

Just curious.... how did you determine "car totally loved it"?

 

I have no idea what is best to use but I can tell you that in Arizona in the summer 10w30 runs off the dipstick like water so I started using 20w50. The temp never gets very cold here so it's not a concern like most of the U.S.
I just chaned back to 10w30 and I noticed that my oil pressure is lower at idle than it was with 20w50 but at WOT the oil pressure is higher with the 10w30.
I also made my dyno runs with the 20w50 an it didn't seem to hurt

 

Ok, i get the second part of x W xx.

So if the wXX is the part of how thick, what is the first part of hte oil number. and how is 5w30 differ from 10w30.

 

The first number refers to it's cold cranking ability. In order to be a 5w oil, it must have a better cold cranking viscosity than a 10w oil. So the lower the first number is, the better it will flow in cold weather.

Here is a quick list of how an oil qualifies for each level:

[code]
Oil Grade Maximum Viscosity (cp)
0W 6200@-35C
5W 6600@-30C
10W 7000@-25C
15W 7000@-20C
20W 9500@-15C
25W 13000@-10C

[/code]

And Arnie, yes the European tests are much harder to pass.

 

I used the Mobil 1 5w-30 for years, but recently switched to the Amsoil 10w-30 because it is supposed to run a bit thicker at operating temp and I want the extra bearing protection at high RPM.

But I am tired of having to order the Amsoil and pay the high price...what mobil 1 product would approximate the properties of the Amsoil ?

 

My car has about 120K on the clock and I've been using Castrol Syntec 10W30 all year round. Would this be bad in the winter up here in CT?