I'm driving from Urbana, IL to Louisville, KY next weekend, a distance of about 235 miles. I have only about 500 miles on my new 2006 Honda Civic Hybrid, so I'm still well in my "break-in period". The car is set up as it was at the dealer (in regards to tire pressure, etc) and is stock. I intend to drive 9 mph over the speed limit with no stops, so I'll probably average about 73 mph. I don't intend to run the a/c, but only God knows how hot it will be that weekend!

So, what's your best bet? I'll post my actual mileage when I get back.

 

When I have the cruise set at 75 here in Indiana's July heat (AC on) I get around 39-41. With your green engine, you may see around that or a little less.

 

I voted. I bet 42-44.

 

I voted 35-39mpg based primarily on the speed. Aero drag gets pretty nasty when you get into the ~75mph range, and even the Civic's fantastic little engine is going to have to burn extra fuel to get the atmosphere out of the way.

 

Yeah, I'll bet the speed is going to get me more than anything else. Just for fun, what would you guess the difference in mpg would be between:

A. 75 mph with the a/c on for 3 hours of flat interstate, and
B. 65 mph with no a/c on for 3 hours of flat interstate?

I have no idea. Maybe I'll drive to Louisville using Option A and drive back using Option B and find out!

 

I often drive from CU to Libertyville, so assuming relatively no wind, I'll predict A) 42 mpg B) 48 mpg.

If you can catch a good tailwind, you may hit close to 50 mpg at 65-75 mph . If you take a headwind, expect low-mid 40s; maybe upper 30s if you are 70+ mph.