I am considering purchasing a 2004 duramax and I have a couple of questions for you all. First, how can I tell if it is a lly or a lb7. The truck is currently four hours away so looking under the hood is not a option. I do have the vin # could a dealer tell me? Also is the lly better than the lb7 I know from past experiences that new designs are not always better than old ones. Are there any major bugs in the new design that I should be aware of? How does the fuel mileage compare between the two? and any other thoughts you guys have. I just unloaded the last ford I will ever own and am looking forward to coming over from the dark side. Thanks

if the 8th digit is a 1, LB7, if it is a 2, LLY. From reading on this forum, I would not say one is better than the other. They both have some "quirks". The LLY has easier acess to the injectors which allows replacment without removing the heads unlike the LB7. Fuel milage is low when the motor has lower milage on it. As the motor gets used and loosens up, milage increases. I am at 18.5 mpg hand calculated with my LLY. How you drive it affects the milage also. If you drive less than 70 on the hwy, you may be impressed. If you drive over 75, it takes a hit. BTW, Welcome to the place, Roy

Not many people have high mileage on the lly's yet. Until they start putting 200k plus on lly's, I'll stick with the lb7. Look at the mileage polls.