I filled up my 1995 TBird with only basic mods, PI intake, & Mark VIII converter (Stock Tune and Full Stock Exhaust) with 0% Ethanol Marine 87 Octane Fuel back home in Steinhatchee, Florida.
I drove 430 miles in 8 hours to Miami taking only back roads (US19, US27, US441, & US1) and
never stopped for fuel!
I filled up in Miami and it took 15.3 Gallons to fill the 'Bird up netting 430/15.3 =
28.1 MPG
Historically, I average around 27-28 mpg, so it's no surprise to me; I will be taking the Turnpike home after filling up with 10% Ethanol fuel to check another tank.
Here is the list of previous tanks I have saved:
Car: '95 'Bird w/4.6L
Mods: PI Intake, polished(inside) Upper, U/D pulleys, CAI, J-Mod, 3.27 Gears, new Front Cats/hollowed 3rd & Aluminum Driveshaft
UPDATE: Ok, after CAI added, I checked mileage on multiple tank fulls of fuel:
1st Tank: 26.1 Avg MPG
2nd Tank: 27.9 Avg MPG
3rd Tank: 25.4 Avg MPG
4th Tank: 25.9 Avg MPG (254 miles on 9.8 gallons of fuel)
Lastly, I haven't done anything to the car in awhile except for disconnect the EGR valve because it was acting up. Took a trip yesterday and got this with a bad tire that was vibrating badly and a misfire when it's cold:
5th Tank: 24.8 Avg MPG (322 miles on 13.0 gallons of fuel)
6th Tank: 25.8 Avg MPG (235 miles on 9.1 gallons of fuel) still need that tune-up, but got two new tires!
Fixed the EGR System (and the tire):
7th Tank: 29.2 Avg MPG (213 miles on 7.3 gallons of fuel) went to Tally
8th Tank: 24.7 Avg MPG (193 miles on 7.8 gallons of fuel) running 90+ mph to Tally about 1/3 of the distance
9th Tank: 28.8 Avg MPG (340 miles on 11.8 gallons of fuel) trip to Alabama
10th Tank: 27.8 Avg MPG (353 miles on 12.7 gallons of fuel) return home from Alabama
11th Tank: 30.0 Avg MPG (244 miles on 8.1 gallons) all highway cruise set at 65 mph to Jacksonville Airport.
12th Tank: 27.8 Avg MPG (317 miles 11.4 gallons of fuel) trip to Ocala, Gainesville, and surrounding areas.
13th Tank: 27.6 Avg MPG (448 miles 16.2 gallons of fuel) trip to Orlando, Tampa, and surrounding areas.
14th Tank: 29.5 Avg MPG (386 miles 13.1 gallons of fuel) trip to Orlando.
15th Tank: 27.2 Avg MPG (147 miles 5.4 gallons of fuel) trip to Gainesville and back.
16th Tank: 28.1 Avg MPG (430 miles 15.3 gallons of fuel) trip to Miami.
17th Tank: 28.5 Avg MPG (433 miles 15.2 gallons of fuel) return from Miami.
Ok, I got a new set of tires on the back - BF Goodrich with a tread wear rating of 700...
18th Tank: 27.6 Avg MPG (334 miles 12.1 gallons of fuel) trip to Gainesville, then down to Ft. Myers.
19th Tank: 30.4 Avg MPG (295 miles 9.7 gallons of fuel) return trip straight home from Ft. Myers.
20th Tank: 30.5 Avg MPG (149.4 miles 4.9 gallons of fuel) trip to Gainesville and back.
21st Tank: 27.2 Avg MPG (152.3 miles 5.6 gallons of fuel) trip to Gainesville and back; showing off a little cost me some fuel
Added front chin spoiler from a 1988 Ford Bronco II:
22nd Tank: 30.1 Avg MPG (454.2 miles 15.1 gallons of fuel) trip to Cumming, GA and partially back to pick up car parts.
23rd Tank: 29.9 Avg MPG (304.6 miles 10.2 gallons of fuel) return trip from Cumming, GA loaded with about 300 lbs parts/tools.
24th Tank: 29.7 Avg MPG (189.8 miles 6.4 gallons of fuel) trip to Perry then Gainesville and back home.
25th Tank: 29.3 Avg MPG (170.1 miles 5.8 gallons of fuel) trip to Gainesville with detour and back home.
26th Tank: 29.1 Avg MPG (192 miles 6.6 gallons of fuel) trip to Tallahassee and back home.
RUNNING AVERAGE (all tanks of fuel combined):
28.0 MPG