Thanks, CLINTO. I agree with Kenny. While some people swear by a certain brand, it really makes almost no difference for the amount MOST of us use our trucks. My only recommendation would be to use a good name brand...Shell Rotella, Mobil Delvac, Valvoline, Quaker State, etc. Most studies seem to show that Rotella is the best. Delvac is also highly rated. I use both Rotella and Delvac the most...but I have also used each of the brands I mentioned above. Basically, I buy whatever is for sale at COSTCO and my trucks have never complained.