I now have a few miles over 7000 on my 06 Cummins. It is entirely stock except for a K&N air filter. Using a mixture of Power Service and Marvel Mystery Oil for the last two fill ups, I'm getting 17.1 mpg for the last 780 miles. That is a mixture of city and highway driving with little regard to limiting my speed or rpms for economy.
The best I'd gotten in the previous four or five fill ups was 16.9 mpg and the worst 15.8 mpg.
I'd used Howes Meaner Cleaner and had got almost 3/4 mpg better on my first tank using but it seemed to drop off. It was probably because I was driving to get better economy more than the additive itself
I'm pleased but hope it gets even better!

 

What ratio are you mixing the two additives at ?

 

50/50 - 12 oz at each fill up,

 

I'm getting 19.5 if I stay below 2000rpms.I luv it too.NO mods except air box mod.4"hose from bottom and K&N filter.

 

Sorry, but I have to ask. Is this hand calculated or from the overhead dream machine.

 

yall are lucky ive got 8k on mine and it is only getting 13.5mpg, i havent had time to adjust spedo, also waiting for the new smarty software

 

Dont feel bad I've got a hair over 16,000mi on mine and its about the same as yours.

 

it's all about rounding up

I get 15-16 with mixed driving.

 

13-14 for me when driving in awful traffic

18-19 freeway at 65

20+ when driving at 50 mph on country roads with no stops


Fuel mileage is all about the stop and go. It takes a lot of energy to get the 8,000 pound mass in motion. At speed it's quite efficient, but over 60 the wind resistance takes its toll. 50 mph seems to be the best speed for these trucks in terms of efficiency.

 

I'm only at about 6800 and lately it seems my mileage has gone down. Driving habits have not changed. I have not hand calculated in a while, but my overhead used to routinely say 13-15 and now its right around 9 mpg. Any ideas????

 

i finally got around to adjusting the spedo (it was off by 2 mph) and i installed the AFE Stage II intake w/Pro Gaurd 7, i filled the truck up and after half a tank i fillid up again, got 16.5mpg, though it was a fluke but the last 3 tanks have been 16 to 16.5mpg, the time i got 16 i was probably averiging 85mpg, cant wait to see what kind of mileage i get if i drive sensibly

also i have had an intakes on most of the truck i have owned and this is the first time i could actually tell a difference, i have had AFE Stage I on a couple and S&B on a couple

 

I'm not babying the truck or am I hammering on it. Power and economy seems to be increasing the last 1000 or so miles. Now I'm getting the "whistle-pop" on shutdown and it is not blowing black smoke if I stand on the throttle.
The 12 oz of 50/50 MMC and Power Service at every fill up seems to be the optimal mixture. Now that it's warming up and in the low 90s, I may go to strictly two stroke ashless oil and see how it works for a 1000 miles or so. I hand figure the mpg at each fillup and have been doing so for several years. It seems to be a good indication of how the vehicle is running or if I am buying good fuel..