As an experiment for one of my college courses, I decided to test how speed affects fuel economy. This was a fun experiment as I was able to confirm other graphs made with different cars
Here is my data:
Temp: 69F
Pressure: 30.29"
Avg Wind Speed: 2.53 mph
Road Length: 0.85 miles, slightly inclined
Speed(mph) South(mpgUS) North(mpgUS) Average(mpgUS)
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25-------------38.5-------------40.5-------------39.5
30-------------40.3-------------43.3-------------41.7
35-------------41.2-------------45.6-------------43.3
40-------------40.1-------------47.0-------------43.3
45-------------38.7-------------45.1-------------41.7
50-------------41.5-------------46.7-------------43.9
55-------------38.9-------------42.0-------------40.4
60-------------36.2-------------38.5-------------37.3
65-------------33.7-------------37.2-------------35.4
70-------------32.8-------------35.1-------------33.9
There you have it. A few things to note: My fuel economy stays relatively the same between 30 and 55 mph. I have a 4-speed automatic transmission, and my car was in third at 45 mph (I don't like how my car doesn't shift earlier). At 50 mph is where I was at the lowest rpm range in the highest gear, hence the jump in fuel economy from 45-50 mph. Looking back on it, I wish I would have done 20 mph and 75 mph runs (possibly higher speeds too) to see a decrease in fuel economy at both ends.
One final note: I acheived 46.4 mpg on the 13.4-mile (starting from a stop and ending with a stop) drive back from the test road. I used pulse and glide between 60 and 45 mph.