CM870 fuel mileage

[Vjex]

Hei guys,I have 07 volvo cm870 950000 miles.I thought I was getting good fuel mileage (7.5-8.5) according to my dash computer.I would reset it at every fill up and would break 8 mph easily. When filed for ifta,my avg mpg came out to be only 6.7 for whole quarter.Its not too bad,but I do a lot of light loads,have tripac apu,so I dont idle at all.When started comparing dashboard computer numbers to actual pumped gallons,I realized that it is off by roughly 20%!Lets say since last full fill up comp shows I burned 178 gall,at the pump to fill'er full I'm ending up with 212 gallons.I didnt expect that thing to be super accurate,but to be off by a 1/5 -thats a lot. Anyways,does it mean I need all actuators replaced?

[Wiseman]

There's to many variables involved when computer calculates fuel used to idle and move . Every little bit of an error multi played by number of strokes engine makes to move from point A to point B , makes huge difference at the end . At the pump we have only three variables. #1-pump calibration, #2-fuel temperature, #3-cetane number and energy contained in the fuel we pumped. Does anyone know precisely any variable? Answer is NO ! As simple it looks, as complicated it is . I personally won't change actuator(s) , ,unless after inspecting them I find they're worn out and ready for trouble. You should be able to find Rawze's video on how to check M&T actuators.

[Marajin]

(02-19-2016 )Vjex Wrote:  Hei guys,I have 07 volvo cm870 950000 miles.I thought I was getting good fuel mileage (7.5-8.5) according to my dash computer.I would reset it at every fill up and would break 8 mph easily. When filed for ifta,my avg mpg came out to be only 6.7 for whole quarter.Its not too bad,but I do a lot of light loads,have tripac apu,so I dont idle at all.When started comparing dashboard computer numbers to actual pumped gallons,I realized that it is off by roughly 20%!Lets say since last full fill up comp shows I burned 178 gall,at the pump to fill'er full I'm ending up with 212 gallons.I didnt expect that thing to be super accurate,but to be off by a 1/5 -thats a lot. Anyways,does it mean I need all actuators replaced?

If it has custom tuning, it could throw it off by a lot. the brain butcher shops are known for making more fuel and the computer does not know it. it makes dash read high.

the ones that brag about giving 2 or 3 mpg more are the worst for this.

[Isx Lover]

I had a tune done by a well known shop from the western part of the US, and my dash read out would be as much as 2mpg more than what I was actually getting. The better my mpg got the farther apart the two would read. Working with Gearhead now and it is much closer than before and the truck runs MUCH BETTER!

[Cuya]

Mr. Hag said Gearhead knows his stuff. i would get in touch with him.

[greg67]

Gearhead is your man for sure. He did my truck and he really knows how to make a CM870 run.