http://www.dieselplace.com/forum/smileys/Star.gif Ive danced around this issue on the forum and have decided to attack it directly. What are the BEST and most COST EFFECTIVE changes or tweaks to a 6.5 turbo diesel K3500 to get the most Miles Per Gallon?? Im not rich, so some $6K add on is pointless so don't list those.


Im sure everyone can relate to this right now with the high fuel prices.http://www.dieselplace.com/forum/smileys/Dead.gif Even more so in Alaska where we had a refinery change ownership and they did a drastic change in fuel prices in just a few weeks.

Well heck noone else is answering. Mine will be obvious. Pour in schaeffers diesel treat 2000 and you will gain 4-7% mpg. Your net savings on fuel costs as an example if you travel 50k per year getting 15 mpg will be $350 at a 4% gain.

Sorry I cant help much, but straight pipe it, and put in a better filter/air intake. It has been since 94 since I owned a 6.5 so I have forgotten what all I did to it. Oh yea I sold it due to injector pump failure every 10,000 miles.http://www.dieselplace.com/forum/smileys/Confused.gif

You might get more reponses if you post in the 6.5 Diesel Engine Section.

Power and performance had 4 times the posts, plus I considered this a performance issue. I guess I could repost there.

An injector pump every 10k bites. Ive had this for 50k miles and she still seems to run pretty well.Edited by: Lotharius

Take the truck to a diesel shop and have your injectors tested and cleaned if necessary...better fuel atomization = better mileage


Switch to synthetic oil in your crankcase, rear axle and transmission


Make your truck more aerodynamic...ditch things like step bars on the sides, get a tonneau or topper, keep the windows up


Don't use your A/C much, and if you don't use it at all certain times of the year pull the belt off and get a shorter one to exclude the A/C compressor.


Lose unnecessary weight (this may mean weightwatchers), extra tools, unnecessary interior pieces/carpet, $50 in loose change rattling around behind your seat, garbage, etc.

How does Truck bed shells affect mpg. Good bad? Im thinking the ones that go from the top of the cab back, or the ones that do that but go up a bit.

Have you cosidered propane? It will increase the mileage proportionately to how much you use. I use it on my Dmax, took it from 18 to 30 mpg. Of course I also use LP, but I figure it has lowered my cost a tad over a penny/mile. It runs quieter and has better power too, it would probably really wake up the 6.5. If you want more info, email me or look at this post in the Second Generation Duramax LLY 2004.5+ (http://dieselplace.com/forum/forum_topics.asp?FID=35)
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<TD class=text width="41%" background="" bgColor=#fefefc>anyone running propane on LLY? (http://dieselplace.com/forum/forum_posts.asp?TID=13899&amp;PN=4)</TD></TR></T></TABLE>

Marcdeluca...are you running propane on gassers? Thats pretty cool....never heard of that before.

You mean you can run a gasser on something other than propane? Yea, I've run the stuff for 15 years, got into when I lived in California and had a neighbor that ran a refueling station. He had most of his cars on it, and it was quite a bit cheaper than gasoline. I bought a used setup and tried it on an old truck, and gradually changed over everything. The '91 in my sig is built for it, has 10:1 compression, roller cam &amp; rockers, makes torque like the Duramax. This Dmax is my first adventure into LP on diesels, and I'm very pleased with the results. I didn't do it for power, although that is a nice fringe benefit. It really cleans up the combustion and quiets the motor down. The more load, the less noise. (At least that's the case on mine.) The oil stays nice and clean also.

The first point of attack on the 6.5 is the exhaust system. Get it breathing and add gauges.

Propane ain't cheap anymore in CA; It's as much as parts cleaner, I mean, gasoline. I drove an early propane-conversion LT1 Chevy 1-ton work pickup back in '80 that would run 2 weeks all over SoCal on 50 gals of LPG, and blow the doors off a lot of fast cars doing it. I don't think it's as economical anymore. They gave me the old 3-on-the-tree POS 'cause I was the rookie but I learned to love the beast. I had always heard the propane conversions were weak.