hi -have 12000 miles on my 2009 tch and have been using regular gas - just tried filling up with mid-grade - put in just under 10 gallons to fill. strangely the gas mileage is much better over 40 - anyone else exlerience this or is it a fluke? thanks

 

The mid-grade might not have ethanol in it. Ethanol reduces your gas mileage. It's only in here to keep people thin i.e. you can't afford to eat corn any more!

 

I have tried mid-grade gas in my 1994 Corolla, 2003 Corolla and a 2006 Ford Five Hundred. In all of these cars I got less performance and less mpg with the mid-grade gas.

Your TCH should run just fine on regular gas if you using a quality brand. Here is the site below that list the better brands to use.

After looking at the list, page down and click some of the links that explains why top-tier gas is better.

http://www.toptiergas.com/retailers.html

 

Depending on location, gasoline might have certain additives (winter gas after Nov. 1, I believe) and other fomulations at different times of the year. All of which could affect mileage.
In addition, weather variations, weight, etc. Can cause mileage to fluctuate.