14L Detroit, Eaton 10spd, 3.70 Gears...

You should be cruising at around 1350 rpms for decent fuel economy so that rear end gearing puts your "sweet spot" around 55 mph? If you are going faster than that then that is your problem! (assuming low pro 22.5's).

My 1995 11.1 liter detroit likes 1400-1500 rpm but I have 4.11 rear so with high pro 22.5's my "sweet spot" is about 55-60 and I've gotten 8+ mpg all summer driving 55-60. I save about $40 in fuel for each extra hour it takes me to get-r-done so less miles per week = more money!

 

Gazoo, the last FL I drove had the same setup, I was getting around 6.5-6.8 (running around 65 all the time). If you slow down a little your mileage will come up, mine would only go down if I was pulling heavier loads (38000 or so) and running up and down I-77.

 

Sorry I took so long to reply, it was a company truck, the 14L det was set to 430/470, 65 mph on the cruise.

An I noticed the same thing, when I could limit my idle time, it made a HUGE difference.

 

Yah, it chaps my posterior that the APU manufacturers lie about fuel consumption at idle to sell their crap. Half a gallon an hour at idle is what most motors burn. Anyways you should get a diesel fired bunk heater, they are only about a grand installed. For four hundred bucks I put in four Interstate ECL (extended Cycle Life) batteries so I can run stuff without worrying about starting in the morning - they can still supply 2000 amps at -20 ! The typical starter develops maximum torque at 2000 amps but only needs 1000 amps to develop maximum power once the engine has started to turn good. You still have to idle if it is going to be too cold to start in the morning - unless you also install a diesel fired engine heater.

 

Might want to check for a website, I'm sure they could direct you to an Interstate battery dealer in your area Gazoo. And for the fuel fired heater, check out Espar.