I just got back from a job interview at Caterpillar in Peoria. I was looking forward to a long enough hwy road trip so I can calibrate my Dashdyno for an MPG correction factor [to get proper mpg calibrations]. My distance calibration was almost not needed – Dashdyno read 394.8 miles while my odometer read 394.4 miles. My only gripe was that when I finally went to fill up my gas the gas price was high for being out of nowhere $3.69 / gal, whereas Peoria had it at $3.37 / gal. But I filled up at a gas pump that maybe was really ACCURATE! After fillup my computed mpg was 22.9476 mpg, vs 21.7 mpg from the overhead computer!

So after my Dashdyno was calibrated I drove over 60 miles at 68 mph and was getting 23.9 mpg from my Dashdyno. Then I sped up at other sections and it seemed I got better instantaneous mpg’s from driving faster at 75 mph! So in all before I hit Chicago hwy traffic I did 113 miles at 25.4 mpg Dashdyno reading, overhead computer at 24.3 mpg. I really think my Dashdyno is accurate enough now, can’t wait for another road trip, next one is maybe Rockford IL for the Vintage BMX show. This time I will try to speed at 75 mph to check for better fuel economy, but usually I don’t like speeding at 75 mph because at that speed you have to be really alert for State Police. And in some states you will see no signs of State Police but they can track speeders – I saw this happen in Texas.

I know hypermilers say go 55 mph for better fuel economy, but if somehow the physics of the 4th gen and because of it’s design – if going 75 mph is best for fuel economy then I’d rather speed at 75 mph! Plus you’d get to you destination faster! So how about you? What is your specific 4th gen [if not listed in your signature] and what hwy speeds were best for your fuel economy? Do you have something to measure instantaneous fuel economy like a Dashdyno or Scangauge?

I drive a 2005 SXT 3.8L with tow package at 127,000 miles.