On my last truck, there was a "change oil " light that came on when it was time.
My new truck, being in %, when do I change it? Also, the dealer where I bought it, is giving me free oil changes every 7500 miles. Is this too far between? On my last truck, a 2001 Z-71, the light would come on at around 6000 miles, but mostly freeway miles. This truck is mostly city driving. Right now there are 1700 miles and the oil is at 80%. Also, if I need to change my own oil in between the dealers free service, what is a good oil to use? I was trying to find another thread I was reading where someone had mentioned costco having some oil for a decent price. One last question, what brand of oil filter do you all recommend? I know this probably sounds pretty trivial to some of you, but this is my first diesel, so go easy. Thanks, Jerry.

I have noticed the computer will determine changing it every 10,000 miles. This depends on how you drive the truck (highway or city) miles. I was going to change mine every 5,000 miles, but for a diesel engine I think 7,500 would be sufficient.

Also, since your dealer is going to do it free, if anything ever happens, you can say, "well y'all changed the oil every time it needed changing."

my change oil light came on at exactly 8500 miles.. but I have changed it twice already.. LOL

Just change it when it gets near zero or when your free oil change comes around. You will get the free oil change, before you get to zero. Your Diesel holds way more oil than a gas truck. If you change it yourself, make sure the oil is rated for Diesel engines. I get mine done at Grease Monkey and use Pennsoil.

Did you buy your truck in Valencia- Parkway GMC? I drove all the way from Perris to there for my 2004 1/2 Sierra SLT LB. They seemed real nice people. they sent me free oil change stuff, but it's too far to drive just for an oil change
:)

mkgd, as a matter of fact we did buy at parkway. Typical weelin' and deelin', but they actually gave us what we wanted for the trade-in. Couldn't pass it up.
And nice people too.

Does the oil life system take i naccount idle time. My box truck has 360 hours and the light has not come on yet. The milage is 5800 and the oil has been changed twice.

supposedly the computer calculates run time, temperature, engine load and a few other variables. Scientific to a certain extent, although I'd prefer a sensor setup that truly lets you know when the TBN is at a dangerous level.

Anyhow I usually run 5000-6000 oil changes well before the light comes on. I change earlier because I just enjoy tinkering from time to time.

The Oil Life Monitor counts also engine revolutions, so idle time is counted as well.