First, why are the D.I.C. options (mph, mpg, etc.) different for the Duramax than the 2004 6.0 gas engine?

The owner's manual says 15-40 is preferred, but 5-40 for temperatures below 0 degrees. But the arrow continues up (above 100 degrees) for 5-40 as well. Which is better, 5-40 or 15-40?

Thanks in advance.

Ben

I think the 05 Duramax DIC is diffrent than the 04-03 Duramax DIC, think I remember someone commenting that the 05 dosen't offer instant MPG and maybe other things are diffrent too.

If your in warmer weather use 15w-40 if it's cold for extended time use 5w-40
Most dino oils are 15-40 and most synthetics are 5-40, I use a synthetic 5-40 year round, others only use 15-40 year round and others switch between 5-40 in winter and 15-40 in summer. To each his own

If your talking about the arrow on the guage on the left side of the dash, that's the tranny temp guage not engine oil. The truck's have no oil temp guage from the factory.
And the tranny temp guage will keep going up when warmer weather hit's or if you do a lot of stop and go driving in the city. Normal is anywhere from 150-200 deg with some higher temps in extreme conditions.

DD

If your talking about the arrow on the guage on the left side of the dash, that's the tranny temp guage not engine oil. The truck's have no oil temp guage from the factory.
And the tranny temp guage will keep going up when warmer weather hit's or if you do a lot of stop and go driving in the city. Normal is anywhere from 150-200 deg with some higher temps in extreme conditions.

DD
I think he's refering to the graph in the owners manual suggesting which oil to use there the 15W-40 goes from 32F up and the 5W-40 covers a broader range.

Ahhhh I see said the blind man


Never mind

I appreciate it very much.