Multi grade oil in a 6.2 Diesel

From: Chris Davis (
Date: Sun Feb 16 2003 - 15:04:18 PST

Hi all,

I've recently picked up a Suburban with a 6.2 liter diesel engine in it. I
know it's not an MV, but that engine was used in HMMWVs, etc, right?

Just a quick question on oil... I am in the middle of my first oil change
for it, and I was about to put 15w-40 in it (since I stock it for the other
family vehicle) but found the placard recommends straight 30
weight. 15w-40 is acceptable, but not the best...

If I remember right "15w" in a multi grade means the oil will flow like a
15 weight cold, (w=winter) but like a 40 weight warm. I've always thought
this "range" provided the best protection for the motor, but now I
encounter a manufacture recommending a single viscosity oil.

Is it a diesel thing? I'm in Southern California, so the lower temp
performance isn't really an issue (hold over from my youth in Maine I
suppose) but does a single weight actually out perform a multi grade?


Chris Davis

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