I've only had mine for a little over 3 months and it seems to get horrible gas mileage. I've read all the previous postings and seems alot have this problem but supposedly it gets better with time. I think fords rating was with a stripped car(just engine and frame) ;)

Mine seems to get really good mpg. It's been averaging around 21. I fill up for about $9.

I used to get about 20 to 22 mpg also, but now I'm averaging between 25 to 29 mpg with mine. That includes city and highway miles. I'm telling you, the Spiralmax insert helped my car out greatly. I don't sell them, I don't work for them, I'm just a happy customer sharing the news. www.spiralmax.com

have you tried just city driving? My highway mpg is 27, i think it's normal. i'm interested in this spiralmax, does it gain more hp?

I don't know actual horsepower numbers using Spiralmax; never had mine dynoed. The company claims it adds HP, and it "feels" like there is more power to me. What I can tell you is that I've noticed better throttle response, and comparing RPMs at the same speeds with and without it, my RPMs seemed to drop 300-500 with the Spiralmax. As for gas, sorry, I'm not patient enough to run a whole tank just in the city.

I have no idea what a Spiralmax is, but I have a question. How does it change your RPM without changing your gear ratios? If your car had 300hp vs 130hp with the same gear ratio at 35mph in 3rd gear it would still be around 2800rpm. The 300hp would just get you to 35mph much faster.