Mobil 1 will cause leaks in older motors that haven't run it because it's cleans out all the **** in the motor so the oil can actually find it's way out now!!!

Bret

 

I always ran 10w-40 in my 95Z when I had it. It was at 115K miles when I sold it.

 

If you have always ran Mobil 1 5W-30 and you switch to say Mobil 1 10W-40, which is thicker if I understand correctly, on a high mileage motor, would this thicker oil make it any harder on the oil pump and possibly shorten the life span? I know it's mechanically drivin', but seems like to me anything thicker that it has to pump would make it harder on the oil pump and lead into drag on the cam, timing chain, etc. Or is it so small of a difference it wouldn't matter?

And going backwards with it, if you currently run Mobil 1 5W-30, is there anything to gain, i.e. easier on mechanicl parts, by going to Mobil 1 0W-30? Guess it would just be easier on startup.

 

The Reason I was asking about 10w 40 over 10w 30 is I know some oils are thinner than others even though they say that they are 10w 30.

I also have owned two LT1 firebirds and a Z28 with the LT1 engine all the LT1 engines I think run quieter with the 10w 30 than 5w 30. I believe the 10w 40 would be healther for the LT1 if you use it during the late spring and summer.

I wanted to get all you folks opinions on it before I actually put 10w 40 in my car.

Thanks Lee!

 

As far as running quiter with 10W-30 vs. 5W-30, it would only be true on startup. Once the oil reaches operating temp, it shouldn't matter. At least that's what this article says.

 

Switched from 5-30 dino oil to 5-30 mobil 1. Only difference I noticed was with a lot of starting and shutting off the low oil light will come on unless it has time to "settle"

 

True and that's when all the problems happen is during the warm up stage. It still takes a very long time to warm up and once that happens the oil is basically the same thickness, which is not the point of having a "thicker" oil to protect in more severe instances.

Bret