7 MPG Pre Egr 12.7 Detroit 60 Series 470?

Well, the general fleet 1400-1500 works quite well for me for many situations. But then, I have to do a lot of two lane, rolling hills, many times with up to 46,000 lb in the box. And that is a consideration that anyone has to look at... what they are doing, and where they are doing it. If I am running the Indiana toll road or similar, I have no problem with lower RPM's, even loaded up on the heavy side, and I take advantage of that. But yanking 46,000 lb of bulk oatmeal or bee barf (honey) on highway 20 in western Iowa and, especially western Illinois from Dubuque to Stockton, or hwy 151 from Dubuque to Madison, WI, these nice neat little charts for general 4 lane flat running do not measure up too well. And low rpms on tougher pulls will rack up some serious EGT's on a Detroit. I rarely bump 900F EGT's even on a hard pull on a hot day. Charts are neat to make generalizations from, but they are only a general guide. And high EGT's are an indicator that exhaust is not flowing readily enough out of the cylinders and manifold. That makes things inefficient from a fuel standpoint also. It takes higher RPM's to effect efficient exhaust flow on a tough pull. Higher RPM's do not always equate to higher fuel consumption. Lower RPM's, the engine also has to deal with fighting rotational inertia. Different engines have differing rotational inertia thresholds. A engine may need more fuel at a lower RPM to generate a given power to the wheels than at a higher RPM if the lower RPM is below the rotational inertia threshold. And while it may take a little more fuel (GPH) to get over a hill at a higher RPM, if the time to do it is less, the total fuel used may actually be less than the longer time it takes to go at a lower RPM and downshifting. There are too many variables out here in the real world to pigeon hole everything onto a chart. And we haven't even talked about turbo efficiency and a thousand other variables.

But we take today... 20K in the box (53K gross). I ran about 1400 RPM / 61 mph all day. Averaged 8.2 for the day (based on fueling tonight) and had a south crosswind of about 10-15 mph. Just had mild rolling hills. Charts are cool for this type of running.

 

The best bang for the buck is the ScanGauge, period. Get your driving sorted and then start looking at the more expensive changes that take much longer to pay for themselves.

Another thing to think about: Use your GPS to track fuel economy instead of the truck odometer. Unless your truck speedometer is spot on, the GPS will give you more accurate numbers.

 

Scangauge D: https://www.google.com/search?q=sca...AUoAQ&biw=640&bih=279#spd=3098580565561969679

 

I came across this post today and wanted to say that you could flirt with 8mpg if you drive it right. I have a 2007 classic xl with a pre 12.7 Detroit and a single over 13, 2.80 rears on 445-50 22.5. I've installed ppm, michilen energy tires and, fleet air filters. Driving in 12th gear (direct) at 58mph with my rpms at 1385ish, no cruise unless it's super flat like Florida and my 30 day average is 7.77. That number is with heavy and light loads from Michigan to Florida and everything In the middle. I use Kevin rutherford's app lets truck to keep track of my mpg. Name on there is (milkin it) the best thing you can do for your mpgs is slow down.