Why the drop in fuel efficiency?

you may have nailed it. ethanol = 10% reduction. and your new route may not be helping. go thru the 'why am i not getting expected mileage' questionaire for more suggestions and welcome to the club!

 

Not sure if this helps or not, When NY changed the additive in the fuel mix. I dropped more than 3 MPG. when using the 10% Cornflake mix I get even worse.

 

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It sounds like you've already given your most likely reasons in your explanation.

I assume that this move means a change in typical weekly driving patterns? Perhaps more shorter trips and less longer trips than before the move? Perhaps a bit more stoplights, stop signs, and stop-and-go traffic than before? Whatever it is, I doubt that your driving patterns are exactly identical to what they were before the move.

I believe Ohio has had a very hot July. Your A/C has probably had to work harder than usual to maintain the interior temp at 70.

Does this mean that you used to keep it in a garage? Perhaps being parked in the sun more often now than before means that the interior starts out hotter on average than when it was garage kept? This would mean that initially the A/C would have to work harder just to cool the car down in the first place.

Yes, if the gas stations you typically used before the move had no added ethanol and the gas stations you typically use now do have ethanol added, it will have an effect on MPG.

 

The first thing to do (as always) is to check the tire pressures. The new mechanic is probably setting them to 35 PSI. They can safely be set as high as the value given on the sidewall of each tire, although the ride and handling will change.

The ethanol in E10 fuel cannot reduce MPGs by more than 3%, except possibly for the first few fillups during which water that was in the tank is being removed by the ethanol. So that is not the explanation.

I easily get 45+ MPG with drivetime temps running 90'F to 105'F and the AC set at 75'F .

 

Hi Richard! I must disagree with your statement. Almost everyone here in FL. I talk to says they lost 10-15% with the E10 we are required to buy. I personally experienced that with my Lincoln Navigator and Lincoln Town Car. ( traded in the Town Car for my 2010 Prius III).
Ed

 

They must be doing something to the fuel in your area because no one else around my area or even on this forum experiences such a drop in MPG. How are you testing this idea?

 

Do you have any update for us on what tires you've got. As in the exact model and size?

 

I think it is a combination of AC set to 70 deg F with the mixture (including heavy congestion?) driving. The tire pressure may also play a role so make sure you check the PSI.

Here is a tip if you drive alone. Once the cabin temp is lowered (from initial inferno), close the two AC vents on the passenger side. That will double the air flow on the driver's side. Point them directly (as per your comfort) to you. I find AC set at 78 deg F comfortable this way. I prefer 76 deg F but on a really hot days above 90, 78 deg F is very cool.

 

I would claim that the simply not knowing what type of tires you have statistically costs you about 2 to 3 MPG. I say "statistically" because there's a strong correlation between not knowing what tires you have and having non-LRR tires.

 

I agree. 70'F seems a bit much, the A/C must be running full blast the whole time.

I keep mine at 76-78'F when it's too hot to roll down the windows (>86'F) or driving at high speeds. I don't like hot temps at all, but 76 is good enough (I'm an efficiency junkie).

 

I just got done using my brothers Jeep for the past month, not running ANY A/C. Now that I've got my car back, even 78 was chilly yesterday and I bumped it up to 80. I find that I tend to start higher, and if I need to adjust during a trip will do single degree increments until I feel more comfortable.

I'd start with a higher initial temp setting and see how that affects things and if you are still comfortable at a higher setting.

 

I am posting this in case the OP is not aware. Plus it is important to mention it.

For a regular car (like Jeep), there is no fuel economy incentive to adjust the AC temp. The AC compressor runs off the gas engine with a belt. The faster the gas engine revs, the colder the AC gets. If you want warmer air, no problem - just mix it with some hot outside air.

Prius AC is full electric with compressor that can run at various speed according to the temp demanded. So there is incentive to conserve and be creative.

 

i get 41.3 mixed mpg (as per MFD) in my 06 prius with 87k...I have brand new air filter, use Mobil 1 5w30, warm up almost all the time, drive it like i stole it (usually), i run nothing but Shell 89 V-Power gas, my a/c is cranked between LO (64) and 71 degrees, and I run oversized 195/60/15 LRR Goodyear Assurance fuel max tires pumped up to 40 psi all around...

EDIT: oh and my car has had all recalls/scheduled service performed (30k/60k and 90k was done early b4 i bought car)

I attribute my gas mileage to my fast driving habits combined with my short work commute (8 miles each way)...I could complain about 40mpg in the prius, but if I got that in my Legend let's say, I'd probably kiss the next random person walking in front of me. So I'm gonna say I'm ok with it

 

My Prius gets better MPG when on the recycle inside air (not the fresh air setting). I get about 48-51 depending on city vs. freeway.

 

Hi! No testing, just speaking from experience and talking to others that track their mpg when they fill up. I have also read replies to readers from the automotive guys in the newspapers that agree with the 10% loss. Florida is considering E15 and scaring the heck out of us. Aside from the mileage loss, the E10 is tearing up all the rubber fuel system parts in our garden power equipment. Bad stuff, E-gas, and our Government subsidizes it!

Ed

 

They are confusing it with other causes; it's easy to do. E10 [1] contains 97% of the energy of gasoline by volume, and is a fine pollution-reducing oxygenator and injector cleaner. (Note that this does not explain or excuse our idiotic tax policies regarding fuel ethanol used to make E15 and up.)

[1] thanks to corwyn for pointing out my previous error