I currently have 113k on my '01 LS1. I bought it with 54k and have used Mobil 1 5w-30 until my last oil change when I switched to 10w-40. Is that the correct weight for the mileage? Mobil 1's website says to continue to use 5w-30, but that doesn't sound right. What do you guys use?

 

5w-30 all day long.

(acutally using regular oil right now until I get enough miles on the motor to switch to synthetic)

 

i have 91k on my car and use German Castrol 0w-30

 

What makes you think that the oil viscosity should be changed at all????

 

I still go by this. Although w/ a high mileage engine, I'd advice a 10/30 Synthetic.

 

My wife's grand am has 158k miles on it and I still run 5w30 and not the high milage crap either.

 

The wear and tear on the engine as it ages. That's what I've always known/been told......

 

The only reason to ever change the viscosity on an older engine is if the oil pressure drops from what it used to be or drops below the manufacturers recommendation. If the oil pressure is nearly the same at 100k as it was at 50k that indicates that there has been no substantial wear to the bearings in that period of time. The necessary visc. is determined by the bearing oil clearances. If the oil clearances in the bearings stay the same then there's no reason to run a thicker oil.
No one can put and arbitrary number out there and say your bearings have worn .002" at xxxxxx miles so now you need thicker oil. Life doesn't work that way. I've taken motors apart at 100k that have very little wear at all (needed a pan gasket so I thought that I'd mic the crank)

 

135k 98 Trans Am 5w-30