Hey All,

I can't seem to find a reason for this. Bought my 04 HCH-1 MT with 114k, everything has worked just fine since then. The Emissions/Check Engine light came on around 120k. Code scan, EGR valve. Cleaned it out, reset code, everything was great up until about 126k. I commute about 65 miles per day, and was averaging (by onboard computer and fill cost) about 46.5mpg for 12k miles.

About 126k, the check-engine light came back on and the car averaged about 43mpg. Thought it must be the EGR valve or o2 sensor, causing poor mpg. Then I received a "recall" notice from the Honda dealer about some software update. So I brought it in, got the software update (I asked them to check the CEL code and they didn't) and after the software update, the CEL was off and I've driven about 1.5k miles, and it hasn't come back on. That's good. Problem is, now I consistently get about 42mpg, driving the exact same route that I was getting 46.5mpg on before! The temperature has cooled a bit from this summer, but Oregon is fairly temperate, I can't see how going from 75* to 65* would make a 4.5mpg difference. Tires are same PSI, driving habits are the same...

Any thoughts?

 

It seems rare for Honda's computer updates to actually improve fuel economy. The same thing happens with the Insight - I tell people not to let Honda touch their computers. We believe the old ones are better in more ways than just fuel economy.

I might have an older revision computer around that you could try.

 

well..ive read otherwise...that the computer update makes the car rely more on the gas engine to diminish the load on the battery cell, extending the life of the battery cell. So the update would actually hurt your mpg. Also, the car will give you alot better mpg in hot days than colder days. In your case im sure the update had something to do with your loss in mpg