Surprising gas mileage on a road trip

[Duc Hunter]

So I just added 285's and Spidertrax spacers to my rig the day before driving to Dahlonega, GA (from home base in Jacksonville, Fl) for a weekend of road and mt biking. We were loaded with gear for 2 people 2 Mt bikes on a trailer hitch rack, 2 bikes inside and no spare tire under the bed (does not fit now). Because of the new tires I took my handy Garmin along to see how far off the speedo and odo were. Well the speedo is off almost right at 5% (reading slower than I am going) and the odo is almost dead on 10% low (less miles than I am traveling).

I run 93 octane fuel, and on the way up I got 17.5 miles to the gallon (corrected for inaccurate odo), while going 75-80mph (avg speed on Garmin was 72.1 mph). Yes, filled up and jumped on the freeway for the whole tank. This was based on the Garmin’s mileage too. I thought “that is a fluke”. On the way back I did the same speed, and got 17.8 mpg corrected! The difference between using my +10% for odo correction or the Garmin’s recorded trip mileage was less than .05 MPG. I kept the cruise set at just under 10mph+ the posted speed limit too, most of which was 70mph down I-95. Talk about impressive…for a vehcile with a 4" lift, essentially 33" tires, loaded as I was, with 80k miles on her and running synthetic engine and gear oils. I just had to share my experience.

[bulldog]

Yep these things can get good mileage, especially if you maintain your momentum, and it is relatively flat land.

[Mikestang]

and it is relatively flat land.

They get even better mileage going downhill. :bigok:

I averaged over 89 mpg coming down from Big Bear.

[Duc Hunter]

True guys but I did it going up and then down.....granted the hills here are not as big as they were in CA

[Redline]

Interesting how our odometers and speedometers are not 'off' by the same percentage, this is what I experienced with my (sold) '05 Wrangler too.

With my 255/85R16 Maxxis Bighorns, my odometer shows to be off about the same, but was actually 11% slow, and my speedo is about 6.6% slow.

But, 255s can be slightly taller than 285s and I didn't do my initial odometer error testing over a long distance so my percentages may come down a bit to more closely match yours.