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Discussion Starter #1
Hi All. I rarely get gas, about once a month-6weeks. My last tank SUCKED. I got 44.1mpg for the tank. Previously, I was getting 50-52mpg on average. Well, I filled up at a different gast station yeterday morning and my mpgs for yesterday were 50.4. So, back to where they were! I know we had some hot weather last month, but i rarely ran the AC and when I did it was in Econ mode. Could it really be the additives in the gas or some other variation in the brand?

(it was really sad to be getting such low mpg's for 6 weeks!)
 

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Are you determining your fuel economy by using the trip MPG guage, or are you calculating it bydividing the mileage by the amount of fuel filled at the station?
 

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Discussion Starter #3
Hmm. The trip guage said 44.1

I went about 450 miles and got 10.2 gals of gas.

Is the trip meter not accurate?
 

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merigayle said:
Could it really be the additives in the gas or some other variation in the brand?
You didn't say what grade or brand of gas you used. Or what the outside temps were. Or what your tire pressures are.
 

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Discussion Starter #5
I do not know the tire pressure. The last tank was either Wawa brand or Hess, i forget. 87 octane. This time, 87 octane Exxon.

I told my husband to check the tire pressures. (he's a mechanic, gotta put him to use :lol: )

It was hot over the past month- sometimes into the 100's. Would the heat, even without the AC on cause that huge of a difference?

The mpg's were actually around 41-42 until the past week when i got them up to 44.1
My lifetime went down too. :(
 

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merigayle said:
Would the heat, even without the AC on cause that huge of a difference?
Outside air temps make a huge difference in fuel mileage. Warmer temps will give you better mpg than cooler temps. But if your tire air pressure suddenly dropped, that could also lower your mpg.
 

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Discussion Starter #7
I will have him check the tires when the rain stops eventually and report back!!

But, if it were the tires, then i would not get better mileage on this tank, no? Maybe it was a whole combination of factors last month.
 

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Sometimes measuring the mileage by amount filled is inacurate. In this case it seems to agree with what the resetable trip fuel efficiency gauge is saying, so this likely is your true mileage. All other factors being equal, warmer weather should increase your mileage. Since this didn't happen you should keep an eye on the mileage for a while to see if there is a pattern developing.
 

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I have gotten some less than ideal gas on occasion. One tank would be normal, and the next would be at least 10 mpg less for the same commute/driving etc. Then the next tank would be back to normal. Temps were about the same, tire pressures ok...etc.
It was a brand name station that I used to do business with almost all the time. I switched stations and I am able to count on my mileage within a couple mpg.
robert
 

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Why is it that the milage is better in warm weather? Warm air should be less dense than cold air, so maybe it's easier aerodynamically, but then it would seem less efficient in terms of the engine breathing (shouldn't effect the electric motor much, warm or cool).

So what am I missing here?

Best Regards,
Rick / CVT
 

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Discussion Starter #12
Rick- i thought it was because the car had to warm the engine and the idle stop will not kick in until the engine reaches 42F? Or did i completely make that up and pull it out my rear??? :?:
 

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http://www.insightcentral.net/KB/faq-co ... html#NoAIS

And AIS is disabled in _ambient_ (outside) temperatures below 40F. Then engine can cool too much if frequently shut down requiring "cold" enrichment. Defeating the whole purpose of AIS (save gas).

Richard:

Complex question. But the most significant factor is believed to be the narrowing of the lean burn window (sorry CVT'rs), aerodynamic drag, stiffer "cold" tires and possible winter fuel blend differences. Plus the additional losses due to longer engine warm-up time.

Also in the hyper MPG range there is such little fuel being burned per mile that radiant and convective heat losses under the hood may play some part too. That's where the cardboard trick helps :!: ;)

HTH! :)
 

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Cold weather reduces the efficiency of the IMA because the batteries are less efficient at lower temperatures. Other factors are tire slippage due to ice, snow, and colder rubber in the tire treads.
 

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There is also a known issue where better than average MPG has been reported just after the tank has been filled. I've noticed it myself sometimes and it has reported on this forum before.

This strictly a guess, but it's probably a flaw in the evaporative control system allowing a very small trickle of gas (instead of gas fumes) in the intake when the tank is full or over full. During closed-loop mode, the ECM will see a rich mixture and lean the engine. Since the MPG meter only counts the fuel entering though the injectors the MPG will go up. Anybody want to experiment?? I read somewhere that the evaporative control system was redesigned for 2006, so honda probably knows it's problem, just does not think it's worthy of a recall.

BTW, If you think you don't fill up your tank often. I've only filled up 3 times this year so far.
 

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Discussion Starter #16
flunky- that is really interesting, because i *DO* get better mpg's right after i fill up. Oh yeah, i rarely fill up either. I walk to work every day so i only drive to the market, the park, and the bank.
 
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