Another oil question....

[Jimamatic]

I'm looking for the straight scoop on why the manufacture gives a 3 month max interval for engine oil change. I have'nt been driving my truck much and have about 3000 miles on 5 month oil. Is there really something to it or is the dealer trying to get you there ($$$$) more often? thx.

Jim

[DmaxMaverick]

3 months?? Never heard of it. 6 months has been the ongoing recommendation (not mine).

If it's your dealer telling you that, ask them to produce the GM documentation. Bet they can't find it.

[Jimamatic]

Yeah! It's in the diesel supplement of the owners manual under short trip/city shed maint.
It says every 5000 miles or 3 months whichever occurs first. Then for long trip/highway you can go 7500 miles or 12 months whichever occurs first
I've always gone by mileage 4-5000 tops for oil change with no regard for how long it's been in the engine. What's it going to do eat through the pan if you don't change it? ;)

Jim

[JohnC]

The problem is that if you make a short trips and the engine never gets fully warmed up for an extended period of time (half hour or so) then combustion byproducts combine with the moisture in the blowby to form acids. Probably won't eat through the pan, but it'll attack cams and bearings and such. Frequent oil changes remove the acids. On the other hand, if you drive it 150 miles in a sitting once a month, then you're probably fine for a much longer interval.