How much does the gas mileage go down with the top down? Has anyone seen a report on this?

It will NEVER stop my wife from riding with the top down. LOL

She loves her 2011 IS 250 Convertible. We average 27-29 mpg with the top down approx. half the time.

 

I don't think you can do better than that...I got 29-30 mpg and I don't have a vert, so that's really good.

 

We just took a 800 mile round trip with our IS250C. We averaged 29.8 on the way and 30.8 headed home. This is Interstate driving with minimal city driving. I drive 70-75 on the Interstate.

We did ride with the top down in Dallas for approx. 30 miles in the city.