A real newbie question. I want to change the oil in my 2003 Duramax. DIC says I have 45% left but I would like a little piece of mind before I leave on a 2000 mile trip. What wieght and type of oil should I use and how many quarts does an LB7 take?

15-40 regular dino oil

or

5-40 synthetic

around 10 quarts

Exactly.


Also, you need to grease the suspension every oil change too. There are 11 points to hit, if memory serves. Some are a PITA to get to, but it's gotta be done. Details in the DIY section...

Should also change the fuel filter. Not too bad of a job, but a strap wrench makes it easier. Hardest part is unhooking the water in fuel sensor connection on the bottom and snaking the filters in/out.

A clean air filter and a clean mas air sensor are important for economy too. The GM filter is one of the best. Cleaning the sensor is also in the DIY section - or detailed in this forum. It's in the air line from the filter box to the engine - can buy spray to clean it.

Best economy is around 55-60 mph. Not that you can easily stand going that slow! It drops off about 10% for every 5 mph over that.

Speed Economy
55 --> 26.0
60 --> 23.4
65 --> 21.1
70 --> 19.0
75 --> 17.1
80 --> 15.4

(table just for example, but it follows what I have seen pretty close)

enjoy,
jb

THanks for the help! I have cleaned the MAF and the air filter is good. I have the tires up to 70lbs. What fuel additives are recommended? Does anyone use an oil additive? I used Z-max in my my gas truck.

THanks for the help! I have cleaned the MAF and the air filter is good. I have the tires up to 70lbs. What fuel additives are recommended? Does anyone use an oil additive? I used Z-max in my my gas truck.
I would stay away from oil additives. Any good oil will have a carefully formulated additive package for the intended purpose. Don't muck things up by adding some magic snake oil to it.

I use detergent and lubricity fuel additives, plus extra fuel filtration. See the tacked lubricity study thread above for some very good info.