High Speed Fuel Economy

My GTPP M82 at 80+ averages 22.x over a 325 mile trip.

GT-SV said:

23 mpg hand calculated at 75-80 in northern CA is what I’ve observed w/2016 GT auto, including many long stretches at 80.

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^ yep that is close to my 23 mpg via my 2016 GT 6 sp auto tranny w/3:15 gearing.

2018 GT Premium, A10, 20" rims, 3.55 gearing. 195 Mi trip w/70-75MPH mostly and averaged 25MPG measured manually. I did not do WOT pulls (no room to drive fast). I get 20MPG average on my daily driving on highway and bumper to bumper traffic.

I have found over the last few years in my 15' GT/PP that highway mileage is increase as speed is increased....my best mileage of 22+ has always come while maintaining 80 mph + or - a few....

FIVE_LITER said:

Shortly after installing my whipple I drove two hours or so on the interstate at 90+ and my on dash reading was around 23. My computer at that time would read around 2 mpg less than what I hand calculated.

I've since calibrated it and got it to read half a mpg lower than what it actually is, but I haven't messed with it for a while. Maybe this spring I'll get it spot on once I get the car out of hibernation.

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How do you calibrate it? My Ecoboost reads about 1 mpg or more high. Thanks.

SVE progressive springs

I recently dropped my GT 1.1" rear 1.4" front and get better mileage but haven't taken a long trip yet to see just how much better. I edit to proclaim a 2 mpg increase due to the progressive lowering springs installed 1 month ago. Less air under the pony matters. Believe it or not?

Likely no measurable improvement in fuel efficiency due to lowering springs.

CurtisH said:

How do you calibrate it? My Ecoboost reads about 1 mpg or more high. Thanks.

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Before you start the car press and hold ok on your steering wheel to get it into engineering test mode or something like that. I don't quite remember what you adjust but somewhere on the forums here there is a thread on all the specifics.

HeavyMetalMonk said:

I measured about 25-26 mpg according to the computer with cruise set at 80-82 over about 50 miles. Rumor is the computer is about 1mpg off.

You can definitely drive 80+ in socal without getting a ticket.

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Is there a trip computer? I'm probably just blind but I checked everywhere I could think of but didn't see one. I figured the fuel efficiency was so bad they just thought why bother.

I have a 2018 GT with the digital IC but I haven't seen anything resembling a trip computer. Although I think I saw a MPG units somewhere in setup menu.

Trip from NC to TX, using 93 octane with Stock Tune. All highway, driving about 5-10 over the posted speed limits 70-80mph... EXCEPT in Missisipi. Just as we crossed into the state, a caravan of F-250's 2500's all jacked up, came rolling past. Trailed them at 120mph for most of the state, execpt when I got a phone call, then dialed it down to normal speeds a few minutes, then when off the call, jumped it to 140 for about 15 minutes to catch back up and then roll at 120 again. Back to normal speeds at the Louisiana border.

The Trip computer said the entire trips economy still held at 24mpg average.

I average about 18.3 mpg with mixed driving, 3.73 gears. Not sure about a pure highway drive yet, but if I could guess, probably 25-26.

NoVaGT said:

Not a lot of people have access to the ability to drive 80+MPH for extended periods (few hours) without getting ticketed.

Why do you ask?

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The freeways in Texas are typically posted with 70 to 75 mph speed limits. So people drive 80 mph.
The toll roads are posted with a 80mph limit...with some sections having a posted 85mph limit.

My car sees extended 80 mph on most trips. Cruising 80 mph....I'll get an honest 22 mpg no problem. I'm sure I could get a bit more if I tried.

Just made a road trip to DC in my Performance Pack GT. On the way down I drove very economically keeping my speed between 60-70 and got up to 28mpg. On the way back to Pittsburgh I drove much faster closer to around 80 for a lot of the drive and my mpg dropped to ~24

2018 GTPP A10 with 3.55...
23mpg averaging 90mph on the way back from WannaGoFast in Dallas last weekend.

From home to Indianapolis, IN. 295 miles in just under 4 hours. cruise set at 75-80 mph. There may have been a few short 100+ mph shots when going around the Chicago tollway! Got 27 mpg per the dash! Very happy with that. Very little wind or elevation change. Done at night with little or no traffic. :cheers:

6M with 3.31's!!