MPG Run #5

[TominMO]

Today I did another MPG run. Very similar to #3, except:
I was going 60 MPH;
there was a breeze of about 8 MPH;
it was about 5-10 degrees cooler than previous runs.

I went my usual route and was careful to fill up the tank exactly the same both times.

The result was a disappointing 50.5 MPG; I was expecting about 56. The breeze shouldn't have mattered much, since my course is a loop around the city; that should have canceled out any wind effect. Maybe air temp was the main factor, but it might also be that this car is significantly more efficient at 55 than 60. At 55 I got 58.5 MPG.

Today I will wash and wax the car, and do a run tmw, to see if waxing gives a surface that is significantly smoother to the extent that it will affect gas mileage.

Note: I did a run at 60 (MPG Run #4) with windows open, and got 48.0 MPG. That is not too different from today's result, but it was warmer and less breezy then.

[JPT]

Did you have the timing advanced on this run?

[TominMO]

Did you have the timing advanced on this run?

No, that's two runs away. I'll let you know.

[thered56]

Wow. Good reason for me to stick to 50 mph on my work commute. That's quite a difference!

[V8Festiva]

On the return from the Ohio meet I got 49 mpg.
Was running stock 1.3 with 5 speed, 12" tires.
Speeds of 65-70
Windows down and no AC
Hauling maybe 100 pounds of Festiva parts.



Dean
Raleigh, NC

[TominMO]

Wow. Good reason for me to stick to 50 mph on my work commute. That's quite a difference!

At 45 MPH I got 62.5 MPG.

[TominMO]

On the return from the Ohio meet I got 49 mpg.
Was running stock 1.3 with 5 speed, 12" tires.
Speeds of 65-70
Windows down and no AC
Hauling maybe 100 pounds of Festiva parts.

That's pretty respectable! Maybe you had a small tailwind? I'm still pretty suspicious of open windows being efficient tho. Just doesn't make sense to me.

[MJD]

Maybe air temp was the main factor, but it might also be that this car is significantly more efficient at 55 than 60. At 55 I got 58.5 MPG.



Tom -- I have heard that the 55 mph is a real good speed for all cars to be their best with mpg. I know in a minivan of ours, we note that 55 is very good, but who on earth drives that on interstates any more ??

:p

I always drive easy going to town and back, and we are in a rural area. Driving over 60 or so in our Festiva is about all I do.

[Banana Bonanza]

At 45 MPH I got 62.5 MPG.

Traditionally think 45mph is about most economical speed for cars. But that was back before overdrives became common. Maybe even 35mph IF you can pull it in high gear without lugging. It really is all about gearing and wind resistance if everything else is the same. Engines all have their rpm sweet spot.

I think to have the discipline to drive at constant 45 on hiway, I'd have to have cruise control. Even then other drivers have no respect for car size of Festiva, they tend to treat them like they do motorcycles. Now my old beater 4wd F250, they stay well away from, its big heavy old thing and would inflict quite bit damage in any crash.

[TominMO]

Traditionally think 45mph is about most economical speed for cars. But that was back before overdrives became common. Maybe even 35mph IF you can pull it in high gear without lugging. It really is all about gearing and wind resistance if everything else is the same. Engines all have their rpm sweet spot.

I think to have the discipline to drive at constant 45 on hiway, I'd have to have cruise control. Even then other drivers have no respect for car size of Festiva, they tend to treat them like they do motorcycles. Now my old beater 4wd F250, they stay well away from, its big heavy old thing and would inflict quite bit damage in any crash.

Yeah, 45 is too slow for safety on the hwy. Someone not paying attention, or annoyed at your driving slowly and making a bad decision can ruin someone's day, so I won't do any more 45 MPH hwy runs.

Yeah, I think 55 might be the sweet spot for a reasonable speed.