Hate to trade my truck with C15 but got a big Mpg education this week with a Volvo

That's fantastic!

 

Me, I replaced the 3:42 rear ends with 3. 73. It's a Columbia with MXS and 18 speed. Power rated at 550 with 1850 lbs, straight torque. I've seen about 1-1,5 mpg better after that but I'm keeping the RPM somewhere near 1400, plus or minus 200.

 

How fast are you driving in 18th to stay at 1400rpm?

 

about 59-60 mph. Actually, I love that. Less stress, better fuel mileage, less repairs. It's cool. Oh! I forgot to mention that I have 22.5 low pro, Michelin multi energy D. I know many people are saying that 1350 rpm it's the good spot but I don't know how, mine is doing better in higher rpm, pulling better and better fuel mileage. I have to admit I'm a little bit confused. If I'm listening to my experience and how do I feel the truck, higher rpm seems to be the answer. If I'm looking at CAT guys lower rpm would be better. But I noticed if the engine is about 1300 before uphill, my boost gauge will go to 45 psi in a second, If I'm starting from 1400 rpm 25-30 psi of boost seems to help enough. The bottom line is that rear end improved the fuel economy. Actually, the best fuel mileage I'm getting when I'm just touching the throttle and even lifting my foot a little bit when the boost is going up. Probably I'm paranoid but even the engine seems to pull better doing that.

 

Hey driver; you spent your money on all the wrong things; like buying expensive sports clothing thinking will make you fit to run.
If you or anyone send me the following info:
Truck make, model. (to check aerodynamics)
Engine make, model, HP, torque.
Transmission make, model, # speeds, final output drive.
Differential ratios.
Tire/wheel size.
The speed you want to cruise (between 55 and 70 miles?hr).
I will tell you what you have to do to get your very best fuel milleage. i will save you a lote of money per year. Just remember that some trucks, Like Freightliner Classic, KW W900, Peterbuilt 379 and others alike can only achieve the best fuel milleage between 56 and 59 mph. Some aerodynamic arrangements need be done.
If you want to race on the road you need not ask anything.

 

Why did they scold u for filling the fuel filters than spinning on do they expect a guy to prime them by hand?

 

as many Canadians do are you referring to 8-9 Canadian or U.S.??? I am Canadian and every guy I talk to back home makes this mistake, there's a 20% difference, and you are also saying 8-9, what is it 8 or 9. if you do a true 30 day average its not 8-9, you will have an exact number, sounds to me that you take your best numbers and brag with them. No doubt those Volvo's are easier on fuel but get your numbers straight if you're going to put your 2 cents in. Just like a buddy of mine who says he gets a 10mpg avg.... funny that his ifta doesn't back this up but yet he still goes on telling people he gets 10mpg with his D13