Convertible aerodynamics

Just finished recording my fuel usage for our BRBS trip.

Great weather on the way down, so topless all the way. Our Interstate mileage averaged 27.5 mpg

Ran into lots of rain, very heavy at times, so top up on the return. Our Interstate mileage averaged 29.1 mpg

Except during heavy downpours, we were travelling at 70 - 75 mph - occasionally a mile or 2 over that.

Would I drive with the top up on a sunny day to get that extra 1.6 mpg? Nope!

[hpwizard.com]

Yep sounds just like my mileage except that i got 27.6 travelling at 70 - 75 mph and that's because I ran with the top up and occasionally ran 3 or 4 miles over too

That's incredible mileage -- that's like 8.5 l/100km. I'm lucky if I get 19mpg (US) or 12l/100km on average.....

Quote
m4240z
That's incredible mileage -- that's like 8.5 l/100km. I'm lucky if I get 19mpg (US) or 12l/100km on average.....

That was mileage I got on the Interstate part of the trip. Once we got into the mountain Boxster Roads, mileage dropped, but permagrin went up.

Around town, I get around 21 - 23 mpg.

I just did a fillup on my Boxster -- you are either quoting Imperial Gallons, or a remarkably restrained right foot....

I'm getting about 12.7l/100km -- average, but, with, admittedly, quite a bit of urban driving.

Quote
m4240z
I just did a fillup on my Boxster -- you are either quoting Imperial Gallons, or a remarkably restrained right foot....

I'm getting about 12.7l/100km -- average, but, with, admittedly, quite a bit of urban driving.

It's US gallons. I did say that it was all Interstate/highway driving.

Mostly urban driving, the difference between top up and top down aerodynamics won't have an effect on gas mileage because of the low speeds.

I seldomly do only urban driving in my Boxster, but around town, it tends to use in the 10 - 11l/100km range.