Horsepower question

You should turn it up, the motor works less thus for you get better fuel mileage driven moderately, We currently are running the mercedes motors and before they cut them back we were getting almost 7mpg. They cut horsepower from 445 to 400 and cut rpm from 2100 to 1650 and we are down to 5.5mpg. It sucks we are lugging them all the time, cut them from 70mph to 64mph. these are company trucks and its for insurance reasons. It really sucks the trucks have started burning more oil aswell.

 

455 wont get much better fuel mileage than 515 depending on your driving what helps the most in fuel mileage is transmission and rear gears matching for best fuel economy depending on where you run. The lowest I would go on rear gears is 3.42 anything much lower will eat your fuel millage up if you have a lot of hills to climb. Highest I would go is 3.58 and some would say as high as 3.70 but any thing higher will eat your fuel mileage up if you run a lot of flat land

 

The best fuel milage tool you have is that RIGHT FOOT not the HP setting... Using common sense will go a lot further than the hair splitting.. I say just set it at the max.. (If your tranny and rears are rated for the torque) and just feather the fuel peddle w/ that right foot, you don't need to drive "flat footed" all the time.. use that head, and some good old fashioned common sense..

 

I hate to be a nitpicker but 3:70 is the "lowest" ratio with 3:42 being the "highest" it's the opposite of what one would normally think. I have 3:70's in my truck and love that gear set in the hills and mountains on interstates like I-81. It's also great on flatlands as long as you keep the rpms down. My truck runs 67 mph at 1500 rpms with 11r22.5's just right. At 72mph I turn 1600rpms.

 

i'm pretty sure 3:70 isn't the lowest, i've seen 3:90's before, they pull great in the sand.

 

keep us posted on how you are making out. we have made a few adjustments to ours and have not found that magic number yet. still not very good fuel mileage.

 

we had ours turned down to 68 mph and were getting awlful fuel mileage , then we turned it up and are getting better now. its weird for sure.