Well it appears I have a problem with my 2006 HCH2 with about 18,000 miles on it in service since April 2006.

When I first got the car, driving it like my Volvo, I got about 44.5 MPG on it, with 32 lbs in each tire. Now a year later, driving with 40 lbs all around, and many tanks at or above 50 MPG, I am now getting 43.5 no matter what I do.

About a month ago, I had a broken gas door cable for some unknow reason, so the fuel latch door was basically open until it was repaired last week. At that time, the mileage went from 50 MPG to 43.5 MPG almost immediately. The gas cable has been replaced, but the MPG is the same. My instantaneous MPG meter shows the engine uses gas the same as always, with most of that instantaneous MPG meter staying between 50-100 MPG almost all the time, same as always. The car performs and drives the same as always. No change.

The only change is that no matter how great that instantaneous meter looks, the results don't reflect in the tank MPG meter. It just wont bump up above 44-45 no matter what. Sad part is, when I take gas, the meter for the tank is accurate.

There are no leaks. The engine /IMAeems same as always, no problems; Assist works/autostop is fine. I mean no mechanical problems at all. SO no leaks, engine seemingly having same fuel use pattern, Instant MPG meter on target, tires at 40 lbs; experienced hybrid driver with lots of tanks over 50 including the car over the summer with air.

I had heard, way back when, something about fuel vapor capture and gas mileage. I simply can't think of anything else, but I can't really explain this. I am looking for ideas or opinions.

Thanks in advance.

 

You and me both. Although I can still get to 50mpg on the trip meter but I really really have to work at it for some reason. I just had my first oil change and I'm thinking the dealer over-filled it but that dip stick, you have to twist it to get it out and the oil is so light colored it is really hard to figure out what the level is (I gave up trying to read it). For me I've noticed on acceleration it is eating more mpg than before and I'm having to rev slightly over 2k rpm to get the same acceleration I thought I did before the maintenance. If it's isn't an overfill then I'm thinking all the gas stations have switched over to E10 and that's finally worked through my current tank of gas.

 

OK. Then my question becomes-- Will a 10% addition of ethanol cause a 10% reduction in FE under the identical driving conditions? My reduction in mileage by hand calculation is exactly 10% interestingly enough. And why can't I see it in the instant MPG meter. That seems the same.

 

Marc,

I was going to mention summer blend fuel... until you stated that you had run it through a summer last year. Very interesting. Only thing I can think of which could cause a dramatic difference in MPG with possibly no other obvious symptoms... is wheel alignment. Perhaps you've hit a nasty pothole during the winter? Tires would still be 40 psi... and steering could (perhaps) still be okay... but with a bad toe-in, you'd be scrubbing rubber (ever so slightly) leading to poor mileage and tire wear. Take a quick look at those tires to see if you see anything abnormal.

One other thing I just thought of... perhaps you've gone through some really dusty / dirty conditions and your air filter is plugged up? At 18,000 miles you wouldn't have changed it yet. Worthwhile to open up the air cleaner and inspect the filter. If you have access to an air compressor, you can remove the filter... tap it to shake out the biggest dirt... then blow it out with the compressed air (or replace it if it looks really bad!).

That's all I can think of for now. Good luck!

 

Thanks for the ideas. First off. I read up and see that a 10% ethanol blend really shouldnt drop the mileage like this. Maybe 3% max; and ethanol has been around for awhile. But I might change gas stations at the next fill up. Which will be like/tomorrow.

As far as dust. Well yes. Houston where I am is an absolute mess as far as construction and I drive through and in it every day/7 days a week. I can change the filter/ but like I said-- the engine and how it performs really is just fine. I dont have any complaints--except after the service recall on that DC Cap thing forced regen comes on more often-- BUT the problem predates the recall by one tank--the MPG is not changed by the recall service.

I actually had the tires aligned not too long ago- still "under alignment warranty" I suppose-- it pulls a little to one side--but not so much.

I really feel I know how to drive the car fairly well as far as my " hybrid-E's" so to speak, and have had no problem getting 50 MPG or higher for almost the entire life of the car. Dissapointing to see this--but I'll stick it out and try and figure this out. I might actually sell the car and get another one if I feel I can get the jump back to 50 with a new purchase-- but thats a ways off for now.

Thanks for the advice-- well appreciated.

 

Try doing your mpg calculations by hand with a spreadsheet for a few tanks. Maybe the problem is the accuracy of the in-car display.

 

Curious, I was just in Houston over Memorial Day and the drop happened after I filled up down there (Though the 270 mile trip back up to Dallas +3 days normal driving was just fine.) I just got the DC Cap recall done also but noticed the drop in MPG right after the oil change (they had to special order the part so I had to come in again). Like you it was around 10%. It seems to have gotten better but I can't really tell as I'm having to turn on the A/C. Currently getting mid 40's which considering A/C and summer blend is about right for me. Go figure.

Have you noticed the instant meter lower than usual on acceleration? That was the biggest thing for me. Also I used to be able to get high instants (above 50mpg) once I maintain a speed around 37mph and up but now it seems I have to be above 40 to get it.

 

I am guessing it is the same problem I am having with my 02 Prius. Its called running the A/C.

With the a/c off and me sweating the mpg is sky high. With the a/c on, I lose close to 8mpg easily if I am not careful.

my 05 HAH is not affected one bit.

Tony

 

If the alignment was done at about the same time as your mileage drop, that could be suspect. They may have aligned to the incorrect specification... especially if it's pulling to one side.

Also, a dirty air filter might not be evident with a performance problem... at least not obvious (especially if it's built up dirt over time). You might still want to throw a new filter in there just to confirm it's not a contributor to the problem.

As others have said, A/C can be an issue, too. Living in Houston... and having gone through a summer already, I'm sure you used the A/C last year. I lived in Houston one summer back in the 80's. I've never been so hot and sticky in my life! I live in inland LA now... very hot in the summer, but dry. I can usually survive without A/C by cracking open three windows an inch. That won't help you in Houston, though!

Wondering if the four mentioned items (summer fuel, air filter, alignment and A/C) have all contributed to bring your numbers down.

 

Maybe some gas is evaporating.
You said they worked on you gas door.
Maybe the seal for your gas tank was accidentally affected.