I have a 2006 Silverado 2500HD Diesel and when I change oil 8 qts comes out even though I think I should be getting close to 10qts. Yes the 8 quarts includes what came out of the old filter. Is there really 2 qts laying around that doesn't get drained!

 

You NEVER get all the oil out of the filter and how long do you let it drain for? warm or cold makes a diff too. 15w40 takes time to drain and yes you will have some left over especially if you have an oil cooler

 

Do you check the oil level before you drain it? Maybe you're burning some oil. Do you make a lot of short trips? Back and forth to work or the store?