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Svtrucking · 10-25-2018, **(Subject: Cm 871 MPG low )**

2010 KW T660 full aero
10sp 3.55 rear 22.5 tires
Cummins CM 871 455st

I’ve had this truck just about 5 Years. Since I’ve got the truck I have yet to see my MPG over 6.0 on regular. My average has always been about 5.5mpg typically drive at around 68mph running produce CA to Fl 43k in the box. I’ve done the whole egr tune up cleaning after watching the Rawze videos and also have replaced the imap sensor, differential pressure sensor. I also clean the back pressure sensor all of this has not increased MPG. I recently had head gasket go out an headcrack at about 800k miles and did complete engine overhaul. All the work was done at Cummins new head, cam rods, front bell housing, turbo, egr, egr cooler, oil cooler all the major components that go along with overhaul were changed. The DPF am DOC new as well with new doser. It’s been a year since overhaul and can’t seem to get better MPG. The water temp goes up to 210-215 on hard climbs and fan stays running. Oil temp stays above 200+. Not sure what seems to be the issue. Could it be something simple as driving? Or some other sensor or this truck is just not spec’ed for great fuel mileage. Any help would be much appreciated.

volvo126 · 10-25-2018, **(Subject: Cm 871 MPG low )**

I would say it's your driving. If you slowed down to 58 mph that would get you 1 full mpg

Lonestar10 · 10-25-2018, **(Subject: Cm 871 MPG low )**

Being from the great state of communist California tuning is most likely out of the question so I would say either slow down or buy a newer truck if you want to run those speeds to get better fuel mileage at least 2014 or newer stars and cascadia's for 7 at that speed with the correct specs

Chamberpains · 10-25-2018, **(Subject: Cm 871 MPG low )**

Its definitely not just "simply" driving. There is a lot of things in ones driving habit that will murder fuel mileage.

Have a read over of this for a lot of good ideas for better fuel mileage driving habits.

http://rawze.com/forums/showthread.php?tid=2855

schISM · 10-26-2018, **(Subject: Cm 871 MPG low )**

(10-25-2018 )Svtrucking Wrote: The water temp goes up to 210-215 on hard climbs and fan stays running. Oil temp stays above 200+. Not sure what seems to be the issue.

I would start with the coolant system. Make sure there’s no signs of belt slippage (bad tensioner).
Plugged radiator/CAC/AC condenser. Water pump (bad impeller). Faulty coolant sensor reading incorrectly. If the engine fan is on alot/all the time it will really affect your mileage. Also don’t forget to inspect your brakes to make sure they’re not dragging(bad slack adj.) or an air valve on the parking brake side leaking causing them to drag. All that extra heat going into your coolant system costs $$$. Good luck.

Svtrucking · 10-26-2018, **(Subject: Cm 871 MPG low )**

(10-26-2018 )schISM Wrote:
(10-25-2018 )Svtrucking Wrote: The water temp goes up to 210-215 on hard climbs and fan stays running. Oil temp stays above 200+. Not sure what seems to be the issue.

I would start with the coolant system. Make sure there’s no signs of belt slippage (bad tensioner).
Plugged radiator/CAC/AC condenser. Water pump (bad impeller). Faulty coolant sensor reading incorrectly. If the engine fan is on alot/all the time it will really affect your mileage. Also don’t forget to inspect your brakes to make sure they’re not dragging(bad slack adj.) or an air valve on the parking brake side leaking causing them to drag. All that extra heat going into your coolant system costs $$$. Good luck.

Thanks for the input. The radiator was pulled when they did overhaul just about a year ago and was flushed and cleaned. As far as the CAC can’t recall if that was cleaned or flushed. I’ve read online it could also get plugged on the inside as well an would require flushing out. No signs of air leaks but will check the brakes again.

Chamberpains · 10-26-2018, **(Subject: Cm 871 MPG low )**

Your CAC shouldn't ever get plugged with anything. Unless you have major internal problems in the engine or turbo failure and you would definitely know. You'd be losing oil very rapidly and complete catastrophic failure shortly there after.

Where your radiator, CAC, and A\C condensor can get plugged, is in the cooling fins. Bugs, dust, dirt, bent fins all can obstruct proper air flow. You can visually check for bent fins, they make tool to straighten them if they're not in horrible shape. If they are plugged with dirt and bugs they can some times be blown out by washing and air blowing reverse the normal air flow (from the fan side forward) If that doesn't work to clean debris then they'd need to be pulled and give better attention.

A quick check you can do is have someone shine a bright light on the fan side of the rad, condenser and CAC while another guy looks on the other side for adequate light shining through or really dirty gunky spots

Waterloo · 10-26-2018, **(Subject: Cm 871 MPG low )**

Take your truck to Mr Hagg, let him fix it. And slow down. ;-)

Svtrucking · 10-27-2018, **(Subject: Cm 871 MPG low )**

(10-26-2018 )Waterloo Wrote: Take your truck to Mr Hagg, let him fix it. And slow down. ;-)

What are the shop details where’s he located. I’m based out of Ca.