I was talking to a guy at work and he was saying that he uses 10-40 in all of his engines, from lawn mower to his Blazer and he swears by it. I have always used 5-30, would it hurt to use 10-40?

I think I am starting to get a leak some where, noticed it today when I parked, I got a sent of something burning and looked under the truck and there was/is something that is leaking from the back of the block where the trans bolts to the block. Oil pressure is staying good and the temperature is normal. The leak looks dirty and thin, I can not get a good sent off of it. I need to pressure was the under side and see where its coming from. But I would like some ideas to where it is coming from.

 

the leak is the rear main seal, most likely. how many miles do you have on your truck?

i run 10-30 in my truck, but have always been taught to increase the viscosity of oil in older, high mileage vehicles.

 

I have 87,7xx miles on it. and I know that most of them are HARD miles, it has been used and abused.

 

i figured it would be somewhere around 100k. most likely it is your main seal. you can go to advance auto or whatever your favorite auto parts store is and pick up some rear main seal repair. the stuff that i used is made by Bar's Leaks. you put it in about ~ 500 miles before you change your oil and it expands and repairs your engine seals.

 

check around your valve covers

I run 5-30 or even 0-30 in my truck. I think there are a lot of misconceptions about lubricants. There was a really good article posted not too long ago about modern motor oil.

 

I used to be " old school" and run 10w30 or w40 in my vehicles.

but the the new engines are built with tolerences that are tighter so 5w30 is reccomended,

And the thinner oil frees up power ( minute but still) and gets to where it needs to be sooner on start up.

Either way i think your fine but i like 5w30 in mine.

 

Thanks guys for the input. Did a oil change and went to 10-30. I will clean the under side and see where it's coming from and also just tighten the valve covers.

 

I use 20w 50 and it really reduced blow by in my turbo app. My pistons were gapped loose for nitrous and this was a good fix. Only thing I noticed was higher pressure when cold but once it's warmed up it is normal.

 

10-30 is only thicker when not at normal operating temps. On cold engine starts, it will take longer to pump thru your engine, thus increasing wear(over time). Once at normal operating temp, the viscosity is the same as 5-30. That's the whole point of multi-viscosity oil. You should consider switching back to 5-30.

On a side note, in the 90's GM determined that using a 40 wt oil caused the rings to stick in the ring-lands(over time). Something about the way it burned off the cylinder walls, and the design of the pistons. Of course, this was in the days of the SBC. I'm not sure if this holds true with the LS engines.