Just got back from a trip to Michigan, from Phoenix, AZ.

Miles there, 2156: gallons of diesel consumed, 118.979 - 18.120 mpg

Miles home, 2112: gallons of diesel consumed, 114.617 - 18.426 mpg

The truck now has 18k plus miles on it, all stock, ('07 2 door 4x4 2500 long bed with a 5.9 and auto trans) and the whole trip was driven with the cruise set at 75mph, engine running just over 2100 rpm.

I didn't drive "carefully" on the pedal, I just wanted to know what it'd get. We drove mountains, headwinds, rain, etc.

My four previous diesels (3 '06 Dodges and an '03 Ford, all quad cab one ton 4wd - and one Dodge was a dually) would get 14 to 16 at the above speed, and better when driven slower.

Kinda makes me wonder what mods to add to possibly gain another 2 or 3 mpg.

 

Drop speed back to 60 and RPM's should be around 1700. MPG will be about 20, so no need for spending cash on mods!! Pour yourself a cup of coffee from the the thermos, sit back and enjoy watching America pass by. You won't have to be as tense and alert at a slower speed! You could have saved 20 gallons of fuel which calculates to about an $85 savings. Modifications will cost you well over $1,000 by the time you do the exhaust, intake and some kind of programmer. Plus you may just end up voiding your Cummins 100k warranty!

 

Drove from Sacramento to LA and back to Sacramento totaling 808.4 miles and used 36.34 gallons without refuling on an OEM tank with vent kit. I managed 22.24MPG hand calculated. I set cruise control at 60MPH and draft big rig as much as possible. Not bad for a truck w/37" tires.

 

Anyone notice the keyword...........60 MPH ?? I have logged 22+ several times at 55/60. ( 2005 W/5.9 auto 2 wd. ) I get 14 pulling a 5000lb trailer.

 

When I keep my RPMs under 2000, my mileage is 21-22 (w/empty truck).

Also, with 18k miles, some might say your Cummins isn't completely broken in yet (but should be real close). I didn't buy my truck new, but I did buy my VW TDI brand new. I didn't start seeing it's best mileage until after 20,000 miles on the odo.

Here's my best mileage: https://www.dieseltruckresource.com/...d.php?t=208012

 

It is said that under 55 your tire resistance is the biggest factor and over 55 wind resistance is your enemy. Therefore if you drive mostly city, air up your tires to 80PSI and if you drive mostly highway keep your speed constant between 55-60 and you should get max mileage. Now if you can stand airing your tire at 80PSI all the time you will get the best mileage. I personally can not stand the jarring I get with aired up tires. I keep mine soft at 45PSI but still mange to get decent mileage.

 

I neglected to mention tire pressure. I usually run 45 or 50 psi. For the trip I aired up to 65psi.

I was tempted to run at 70 for a few tanks, but we were on a travel schedule, so 75 worked for us. I may try a slower speed on a Los Angeles trip. I never got that mileage though on my other trucks, they were larger and heavier, so that may be the difference - but I am very pleased with the mileage.

 

I had read that if you don't tow, you won't see an increase in mileage until you hit ~ 25K. That's exactly what happened to me.

Tip mileage used to be ~ 20-21 on average. Now it's 2 mpg better.

Speed kills.......mileage.

 

Intresting results. Have 227,000 on Blue Beast and injector went down. Over fueling and bad diesel knock at idle. Purchased a set from Pensacola Diesel for 217 bucks. Just cheap replacements and supposedlly a little more power. Fixed issue and miss gone. Had been getting about 17 on OH console when pulling trailer on 600 mile trip. New injectors got 22.5 on OH console and a real 20.6 MPG.Remember this is with 4,000 pound trailer and load in dually bed. Wish had replaced some 50,000 miles ago when first noted iregular vibration(miss) as now know. Summation: Don't hold off too long on replacing injectors.

 

I swear I get 25 mpg if I can drive a constant 45 mph.
But where in this world can you drive like that?
On the road I get 18-19 @ 70-75 mph. And my truck is a hot rod!
I got 57K on the clock.