Originally Posted by
Diesel Dimwit
I just acquired an '05 LLY and am disapointed with MPG. This is my first posting so bear with me. I'm sure this has been explored a lot, so I apologize for raising it again but I'm having difficulty trying to figure out what I can do with a limited budget that will give real results. I'm considering some sort of intake system, but am concerned that it won't help much. Also, I'm thinking 4" exhaust but I doubt that cat back would really do anything. I'm not wild about violating MD's emissions requirements by replacing the cat, but may have to. Would installing a larger 4" cat help or does anyone even make one?
What are you getting for fuel economy and under what conditions? On my LB7, I replace the exhaust with a 4" unit, installed a performance intake, a performance program (Edge w/Attitude Monitor) and a BD left side exhaust manifold. Cost: $2000. Mileage gain: 1mpg. The power? Different story, this was a measurable improvement. So, depending on what you are trying to accomplish, don't spend more money than you are going to get back. I think it is safe to say that the exhaust and intake need to be done together, and I would not expect any mileage gains, though some would differ with me. The tuning with the programmer, or having John Kennedy tweak your computer will probably get you the best bang for the buck on mileage. The display on the dash helps me control my driving habits. Drive by wire systems don't have a very good feel to them, and my monitor tells me exactly how hard I am pushing it, thus helping me to drive more conservatively, particularly around town.
If you are towing a fifth wheel, see my posts on the trailer towing forum regarding a wind deflector.
Take a look at the gas mileage polls under Duramax 6600 forum to do a comparison to what you are getting. It does seem that some just do better than others, without much of an explanation as to why.
Owner, Phil's Auto Clinic, Hemet, CA, 1997 Napa/ASE tech of the year
2001 D/A Crew cab long bed, Edge Juice w/Attitude Monitor, Banks Exhaust, S&B intake, BD exhaust manifold, 152k miles, 2nd set of injectors 06/25/07
2000 Powerstroke Ford Club cab short bed, Edge Juice w/Attitude Monitor, 5" exhaust, S&B intake