Did this for my '09 Fit over the weekend, I hadn't been getting more than 30 mpg hwy, which is pretty bad . 35 is more normal, 32-33 city, running 100% A/C, auto trans, no cruise.

Pull the throttle body intake hose, attach the intake cleaner spray tube in front of the butterfly, then re-attach the intake hose. Solvent feeds from the can at during high idle (+500-1000 rpm) for about 15 mins. I used an adjustable broom handle against the seatback to hold the fast idle. When done, spray cleaner into TB, removes deposits very well (I had some varnish around the butterfly where it closes etc). Safe for all downstream components. My CEL came on but went away after 10 miles or so. Finally add tank cleaner, fill 'er up and go for a drive.

So far, after almost 1/2 tank on the cleaner, number are more normal again, 35 hwy and 33.7 city . Bottom line, it gave me noticeably improved mpg. At 45k miles it's never been done before. Tailpipe finger wipe has always been super clean, but lately a shade of grey before cleaning. $37 before $10 rebate, once a year will pay for itself. Ordered a K&N flat filter to let her breathe better too!

How-to demo video:

 

I did a similar procedure to my 12 year old Infiniti i30 with 175k. Running rough especially at idle. However I used sea foam and I ran that through the brakes vacuum lines. It fixed the rough running that's for sure. However my mpg didnt seem to suffer or get better with the problem and fix.

I''m surprised a car that young would need that. Don't really care for the oil coated air filters though. Whole thing with those are the pores are bigger to let more air in, any dirt now gets stuck by the sticky oil the that spray on there.

 

I thought the same way. But mileage was down, didn't believe ethanol content wad to blame. Same driving habits & gas. There were deposits and mpg improved after treatment. I have used K&N before on a previous Civic. Works well. Clean up with dishwashing soap once a year, dry and re-oil, no probs.

 

Interesting. I've used the Valvoline 3 step system that feeds through the brake booster before on many cars and it made a huge difference when finished. All of them were very old and high mileage though. I am kind of suprised it made a difference on a car with such low mileage, I am glad it worked for you

Debating this or seafoam at 100k now... where did you pick up the 3M package?

 

It's on Amazon, find 3M 08963 Fuel System Tune-Up Kit for $37.07 free shipping. There's a $10 mail-in rebate if you buy before July 31. Print out the rebate form here:

http://g-ecx.images-amazon.com/image...373784406_.pdf

The kit did what it claims and is simple to use. Unlike single-point tank-only solvents (used Techron before, no difference) this covers the entire system. I feel this is maintenance just like changing oil. I plan on doing it once a year. As long as you are burning a petroleum fuel, which will leave some deposits over time, periodic cleaning is needed. Even the Fit, which is an ULEV vehicle, is only as good as the gas you're stuck with . I use Mobil 1 0W-20 to help avoid problems there.

 

Ouch even with the discount the sea foam is less then half price...