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DDlighttruck · 10-01-2019, **(Subject: Fuel mileage )**

2003 CM870 in a 2005 9900i. 3.70 gears, 13 speed. I try to keep it around 60-64 mph, and in the 14-1600 range for rpm. Hand calculated, I'm showing an average of 5.95 MPG for the last 20,000 miles. One tank that had to be a mistake showed hitting 7.4, the worst was 4.8. It's been as low as 3 mpg in the winter

When the ECM was "looked at", I was asked if I wanted power or fuel economy. Foolishly I asked for power. I was off road a lot, all flatbed and stepdeck work. Now I'm running a lot more highway miles and realize I made a mistake.

So is that my first step is having a fuel economy "setting" done to the ECM?

I've gone through the excessive fuel consumption tree on Quickserve, and I think I've pretty much got it done. Overheads been done recently, low-pro tires now, exhaust is tight and no obvious leaks, CACs been done (although hasn't been tested in awhile), EGR tune-up was done (150,000 miles ago), de-mandate at the same time the ECM was "looked at" (by one of the guys recommended on here), no check engine lights, I keep up on the maintenance of the filters and fluids. New CAC boots recently too, and new clamps.

Pretty much the last three to check are for any leaky injectors, fuel pressure and fuel restriction. Well, I should have someone more knowledgeable check my turbo, actuator, and actuator controller. Probably pressure test the turbo and CAC too

Is this about the best I can get from driving a brick down the highway?

hhow55 · 10-01-2019, **(Subject: Fuel mileage )**

My fuel mileage improved, when started running 1600 rpm's in 12th gear instead of 13, and keeping my boost at or below 10 lbs as much as possible.

tree98 · 10-01-2019, **(Subject: Fuel mileage )**

Who did your demandate?

DDlighttruck · 10-01-2019, **(Subject: Fuel mileage )**

That’s what I’ve been running, 1600 in 12th (8 low)

One of Unilevers guys did the demandate remotely

Just keep in mind I have zero complaints with the demandate and work performed, they are very knowledgeable and were very helpful in fixing a few other things on my truck. I’d recommend the shop to anyone, if asked!

Chamberpains · 10-02-2019, **(Subject: Fuel mileage )**

What horse power are you set at currently? What region are you primarily hauling in?

DDlighttruck · 10-02-2019, **(Subject: Fuel mileage )**

If I remember right 525 horsepower. I run Ontario/Quebec, the mid-west and the northeast primarily. Some southern runs, some western runs, some east coast

Rawze · 10-02-2019, **(Subject: Fuel mileage )**

pressureize the whole engine to 30 psi. Check for leaks.

Chamberpains · 10-02-2019, **(Subject: Fuel mileage )**

Being a big square Hood and an old cm870 you should be able to squeak out mid 6's into the 7's on fuel mileage. What tires are you running? there's also a lot of fuel mileage in having good driving habits also. Look into hypermiling on here

SIDE_SHOW · 10-02-2019, **(Subject: Fuel mileage )**

when i went to rawzes last week with my truck anf he helped me out i was getting 4.5 to 4.8 rawze drilled me the whole time i was there about running in neutral as much as possible higher rpm and lower boost and slower speeds 58-62 and im happy he did... i have a 2007 pete 386 with an 870 13 speed and 3:36s and first trip from rawze went to ATL to MS up to CT all loaded miles with 40k i the box over all those hills and averaged 7.3 or so on the first tank... you have the rears i want becuase my milage will jump up even higher when i put lower rears in it... i am set at 400 and 1550 torque i go no where fast and takes me so long to get anywhere but i ran 4100 miles this week and saved myself over $1000 in fuel so i dont give a dang if it takes me 6 hours to make 300 miles.... you should read his write up on hypermiling its on this forum somewhere its a good read...
you can rad it here http://rawze.com/forums/showthread.php?tid=2855