Took a trip to Calgary and back on the Speed3. 1500 km round trip (just shy of 1000 miles).
On the way there, I used the throttle for passing, and stayed somewhere in the range of 80mph, kissing 100 mph when passing trucks. I hit 125 mph once because it got there so easily.
Topping off at city X, I had 490 km on the trip, quarter of a tank left, first click was 41.3 liters. I think you'll find that equates to 8.37 L/100km, 3.7 litres to the gallon and 62 miles in 100 km makes that equation 62/2.26 equals=
27.4 US MPG exactly what its rated for highway.
On the way back, I decided to perform a little test. I stayed UNDER the speed limit (a first for me), stayed off the throttle for passing except just mild speed gains to avoid stones from semi trucks. I rarely had to pass

I didn't allow the throttle to close downhill, and used that momentum to and gravity to slow me down uphill with the throttle in the same position, tried to get the car to settle at its cruising speed of about 68 mph at the crest of the hill. I had to estimate the liters because the jackass gas station forced me to PREPAY under their 24 hours prepay rule >

I put in as much as I dared, 41 litres, I heard it go up the neck just before I ran out of the $60 I put down, so I'm correcting to 43 for accuracy (warning light goes on at 45 liters down, and it was not on yet).
The total? 710 km! And the fuel light was about one hair from turning on. Trip computer said 53 km left, although 30 km went missing in the last ten minutes of the trip back, as it got increasingly pessimistic.
Thats 6.05 l/100km, or
37.9 MPG! If the OP was going 60mph, I validate his fuel mileage claim.
EDIT: Coincidently, my 94 civic DX consistently got 38-40 MPG consistently no matter how I drove. 38 If I aggressively passed and 40 if I tried to wring the miles out of it. And that car had 1000 lbs less mass to move and had a motor 160 hp short.