Quote Originally Posted by Fozziekyu View Post
I tried one bottle of Techron , unfortunately I feel nothing has changed ,I guess this is just how Mirage is

but I find out Costco give me bad MPG while Shell give me best MPG, I got a 27mpg with no traffic at all in SF City.... lowest in history

Shell could get my car reach 45mpg in highway and Costco will only make 36mpg in a similar trip, not sure why though
Outside air temperature has a big impact on the fuel economy of the Mirage. Not sure if either tank of gas had a similar operating environment..