Hello guys. I have searched around and searched around and havent really come up with the answers ive been looking for.....

I HAD a 1984 C-10 6.2 which averaged 24.9MPG, and thats doing 75 on the highway, 50 backroads, and it had a stack....so i did hammer on it.

I HAVE a 1999 K-3500 6.5 now, and to say the least, my mileage is pitiful. I drive 65 on the highway, 45 backroads, no stack, straight pipe.... take it easy, and she goes through about $100/wk in diesel (and I work and go to school only 8 miles from my house). I think the last time I checked, i maybe got 14-15.

I have 245/75/16 tires, I assume 4.10 gear (being a one ton SRW). I replaced the injection pump (and put it back where the old one was......I was told the timing isnt too critical on the 6.5 {computer controlled?}) The truck has a fresh alignment, and I have a lightbar on the top.....

Is there anyway to see the 20MPG range? I was told that running 235/85/16 tires at 80PSI (because of the pizza cutter effect) would be good for a MPG or 2. Is their any other tricks to pulling some more MPG out of this old girl........

I hate to get rid of the truck, but at this rate ill burn more money than I make.

 

I think I'd probably get the timing checked first to optimize the base timing and allow the computer to adjust from the best starting point. Is the eight miles to work and school mostly down an open highway or stop and go through town? If it's mostly highway, taller, narrower tires might help, along with aerodynamics. I made a crude air dam from plastic semitractor mudflaps, fitted it under the front bumper, and gained a couple mpg on the highway. Make sure to leave at least 3" ground clearance, it kicks up too much gravel at two inches, the main goal is to keep as much air as possible going around the truck rather than under it. Is the light bar necessary?(Kind of want one myself, but I have to ask.) Wait, offroad lights or emergency lights? Either way, can you fabricate some sort of removable set up to get them out of the wind? Then remove as much unnecessary weight as possible. I guess that's about all that pops into my head, hope you can get some good out of it, keep us posted

 

haha yeah it is, I'm a firefighter for our town.

 

Thought that might be the case. You might look into dash mounted emergency lighting, and led strobes for the front and back of the vehicle. Check out Truck-n-tow.com, they have a wide variety of lighting options and other vehicle accessories.

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Even if you keep your existing light bar, might be good to add some more lighting to your set up. Get people out of the way quicker and warn them what's coming up.

 

My 83 6.2 on 35's with no od does mid 20's no matter how I drive it. The best I have ever got out of a 6.5 was 19mpg. The 6.2 has smaller pre chamber exits which is probably where most of the fuel savings comes from.