I always learn something when I have my S serviced. My mechanic suggests 10k miles between oil change, but 5k on filter. Just had that done plus determination of check engine light which popped on after my last fillup. I have always used93 octane if I can find it. He concluded my problem was a misfire in number 4, most likely bad gas. He said 93 obtain doesn't sell quickly enough due to price and its ingredients separate. So when you fill up you can get excessive water content, especially condensation from hot muggy weather.

He recommended 3 12 ounce bottles of Techron System Cleaner in a full tank of gas and drive the car hard to clean the crap out of the tank, rails and injectors. Cost $20 at Wal-Mart. He would do the service for $150. He feels the purest gasoline comes from BP and Shell.

Any thoughts?

 

I would definitely buy gas from a Tier 1 supplier (Shell is on that list, about all I use when I fill up the S and my Prius).

As for the gas being the cause of the misfire - it is possible. If it keeps happening however, then gas is not the culprit. At a minimum, you should check your coil packs to see...switch them between cylinders to see if the CEL/code follows. If not, then it could be the gas or an actual issue with the cylinder (not sure why one cylinder would have a gas misfire vice others).

 

He did that analysis. Some of it was over my head. He said Honda does not return unused gas to the tank, but knows how much is left in the rails. Number 4 is the end of the line and most susceptible to accumulating residue.

I may not have gotten that all correct, as I said he was over my head. I will update the post after a tank with Techron. I really respect the guy, he is a Purdue engineer and very upfront. He has carte blanche on the car because he knows I want it right. He has never abused that.

 

I see you live near Indy (didn't even look until you mentioned Purdue).

Buy your 93 octane in Zionsville or Carmel; I guarantee you it turns over quickly enough to make that theory a non-issue.

Side note: every car I've owned has run 93 octane and I've never once had a problem with a bad tank of gas (at least not bad enough to feel it while driving or have an overt problem that required any sort of intervention on my part).

 

Shell V-power is my favourite as they don't use ethanol in that grade of fuel in my region.

The best fuel injector cleaner is Redline, it is one of the few fuel products that is strong enough to work with one treatment, one bottle does 2 of our tanks. It contains PEA as does Techron, but at a much higher dose. Techron is good but I prefer Redline.