best speed for best mpg

[weatherdan822]

does anyone know at what speed you get the best fuel mileage? I have an 04 hatchback with a 4 speed automatic. I've done fuel runs at 65 and also at 70 mixed with some city driving for both.

 

[destineal]

Well what are your numbers from your fuel runs?

 

[weatherdan822]

Well, you can click on my fuelly link above ^, though typically for a mainly 65mph fuel run, I get about 320 miles at ~29 mpg whereas at 70 I'm not too sure because the only full 70mph run I've had I did a fair bit of idling near the end right as I got to about 315 miles so the data was a bit skewed, although I did manage 33 mpg for that trip. It seems a bit counter-intuitive though because I've always read that 65 will always be your max mpg speed. Thoughts?

 

[WillD]

0mph

I couldn't resist.

 

[weatherdan822]

haha, nice ^

 

[b5a4]

I have 2005 3s hatch with the 4-speed auto and have been averaging 29mpg with 30:70 city/highway driving. As for the best speed, typically slower is going to be much more efficient because you are going to be at lower RPM, less drag etc.... I am interested to see how much a difference in mpg you would get from 65 to 70... You should try it again using the same section of road for consistency sake and see if you are getting any difference. I think that maybe filling at a different pump, weather conditions, tire pressures, different roads and other factors are why you were seeming to get better gas milage at 70 than 65mph

 

[dgross7]

If I use a whole tank on the highway, I normally can get close to or break 400 miles. I think it's hard to say a specific speed is the best because there are many other factors to fuel economy