Anyone else worried about carbon build up on the intake valves? Supposedly it's a big problem for gas direct injection... Gas doesn't wash the valves. I'm thinking about running a spray cleaner like CRC though the intake. Any thoughts on this?

Just run a high quality detergent rich premium gasoline for a couple tanks, i reccomend chevron or shell 91. If you could see the inside of the l15b1 combustion chamber, you would notice the DI injectors are placed just behind the intake valve seats, when the piston is on its compression stroke, fuel actually sprays the backside of the intake valves before they are closed. Honda was very intelligent to do this. Please avoid poor quality gasoline and run premium every now and again (or full time, like me) and you will have no carbon coking issues.

Hope this relieved your worries a bit. Read up a few posts in this thread for more information on the subject from myself and GAFIT.

What you are doing is plenty good to keep your DI system running clean! Running 91 octane exclusively is more or less so you can force tune the ECU to set a base map for that Octane, and in turn you receive more power, better fuel mileage, and in my opinion a much cleaner fuel injection system once the ecu has adjusted to a higher octane, long term mapping.

By using chevron 87 you are Already doing more than 90% of the people here who apparently fill up on "the cheapest they can get", combine that with the fact that you have the common sense to run a tank of Premium every now and again you're definitely on the right track to keeping your l15b1 clean and happy.

Thanks for the feedback.
I guess I'll stick to my usual routine.

I admit, I realize I'm probably wasting time and money with my occasional, random, "blue moon" tanks of premium.
But I don't do it very often. If any "improvement" I notice is purely placebo affect? Well, I'm OK...I'll pay for that placebo affect.

you're doing great, and don't worry the Blue Moon tanks of 91 octane are actually quite beneficial. 91 Chevron has a lot more detergent in it then mid-grade and 87, mid-grade is just a mixture of 87 and 91 I believe at a rate of 2 parts 87 and one part 91 so you're definitely doing a good thing for those direct injectors. They love the techron!

We should organize a Honda Fit meet in the East Bay somewhere. Not sure if you'd be down for that..would be awesome to see other GKs and other generations of Fits, collab and share knowledge~

Thatd be great! I would say ANY honda welcome but, sometimes that brings in a rough crowd out here 😂. Most of us fit owners are older and have our shit together ironically enough, i could see it being a very cool chill information rich meet.

ive read about it but usually i sell my cars before they hit 50k so im thinking this will be an issue for the next owner(s).. so no, i doesnt really think about it. plus, dont they offer some sort of special cleaning service at the dealerships after 50k miles or so? probably good to have that done if you plan on keeping the car for a long time.

seems most car manufacturers are only concerned about the first one or two owners or renters, and by the time the car reaches 50K+ they want you to buy a new car.