93' Convertible Cavalier.... Roof up and Down Comparision

[andrew54]

So I just took a drive from Toronto To Montreal in my Vert. ~550km each way.

On the way there, I drove 100km/h with the Top Up, and Windows up. During the morning. Acheived 32MPG.

On the way Home, Same Speed, but Top down with Windows up. However, the night was much cooler, and required the use of Lights, and Heater on full. Got 30MPG.

So now Im not sure if the much cooler outside air, combined with the additional draw by the lights and heater could be More than 2 MPG, but that atleast gives me the indication, that there isnt a big difference.

Does anyone think that these varances could be more than a 2MPG difference?

[JRMichler]

My truck's mileage changes 1 MPG per 10 degrees F. The electricity for lights and heater blower is worth a few tenths of an MPG.

Another variable is wind. Five MPH of headwind or tailwind will affect my mileage by about 1 MPG. A crosswind has the same effect as a headwind.

Another variable is elevation change. I regularly drive about 60 miles with an 800 foot elevation change. Downhill averages about 5 MPG better than uphill.

Your mileage, of course, will vary.