Good morning,

I have a 2006 Civic Hybrid II with 65k on it, and I have been enjoying a 48 mpg average over the lifetime of the car. I religiously use 87-Octane Chevron gas. About a month ago, I decided to do a little system cleaning, as I do about once a year. I put in a tank of 93-Octane and a bottle of Techron additive for a little extra cleaning action, like I've done in the past. Since then, my tanks have been dropping from that 48 mpg average down to 38-40 mpg almost instantaneously!

My driving habits haven't changed, and I'm quite judicious with the A/C as the temps haven't really gotten over 90 yet. I'm truly stumped.

Is it possible that the Techron threw something off with my engine control unit? Did it loosen something that's clogging something else (which seems a little unlikely)? I'd appreciate any thoughts of what might be going on here.

Thank you for any help you can provide.

Jeff

 

I wonder if the higher octane caused the car to adjust the timing and now it's taking longer to relearn? I would try a power reset and see if that brings thing back.

 

Thanks Brian. This morning, I disconnected the battery for a full hour to ensure that the memory would be erased. After reconnecting, I went to the corner gas station and topped off the tank to start fresh.

I'm finding, at least initially, a mixed result. At constant velocities, I can pull around 50mpg. It's the accelerating that's killing me. Gas seems to be dumping into the engine. While I used to be able to register about 5-6 fuel bars (25-30mpg) during acceleration, I'm getting about 3-4 fuel bars (15-20mpg) now. It's still feeling sluggish during pickup, and the engine is butting up against 3k rpm as opposed to the 2500 rpm I used to experience.

Perhaps the computer needs a little time to relearn the process (at least more than 15 miles)?

 

Jeff,
How's this going, have you returned to your previous mpg figures?

 

You might want to consider the possibility that the fuel treatment is purely coincidental. It's possible you are suffering from the dreaded battery pack decline @ 65k, I would also have that checked out, are you running short on charge bars a bit faster than usual.

Otherwise it's possible that the additive fouled a sensor, hybrid cars are a different beast and with their Psudeo-Otto-cycle engines they have added sensors and such to foul up. I would have the car scanned for pending codes and refrain from adding anything to the tank other than gas or have a "real" fuel system service from a shop who you can take up the issue with if they use improper cleaning fluid.

 

Andy, I'm still running around 40-41mpg. Now, I'm sure that an mpg or two is due to the fact that it's been in the upper 90s in Houston, and the hamster running my A/C unit is having a coronary.

I'm going to take the car into the shop and get the thing scanned. This is really disconcerting...

Jeff

 

****. We ran the gambit of codes, and came up empty. Since it practically was the same cost of the diagnostic (which the price was deducted from), I had them flush out the fuel system. If that doesn't do it, I'm going to have to reconsider this thing. I had a series of other recalls taken care of as well. I'm really not one to ditch a car until I absolutely have to (breakdown, flood, etc), but I may have to say sayonara. Fingers crossed...

Jeff

 

what kind of gas to you guys use? regular or premium?

 

Regular (eastern Ontario, Canada, so it also has up to 10% corn based alcohol additive........)

 

My vote would be that you used "premium" in an engine designed for regular. Or, 93 octane when your vehicle calls for 87 (or maybe even 86?) octane. Maybe not fully contributory to losing 10 MPG, but definitely part of the problem.

Regular, Mid-Grade and Premium are misnomers. Marketing terms to get you to think the higher octanes are *better*.