I just don't understand what's going on. I'm at 6370 miles and I'm driving mostly city miles (lots of EC) and my mileage is going south - and quickly!
During a road trip I took to North Carolina last month I was able to get 32 MPG - driving up to 85mph and going uphill through the Smokey Mountains. Now, I'm back in Houston, I'm driving in EC mode A LOT and the weather is a bit cooler. I just entered my last tank of gas and it's down to 28 mpg!!!
What am I doing wrong? I checked my tire pressure - 44 psi. I thought the mpg were supposed to improve after I broke-in the engine. I thought that I would see it improve even more after around 6000.
Does anyone have any advice? Thanks.

 

Cold weather significantly affects MPG in all cars. It is especially noticable in your FEH (and my Prius) for two reasons:

1 - The ICE runs more to keep it, its catalytic converter and you warm.
2 - It displays the MPG to you at all times and we are hypersensitive to it

One thing that helps here is the addition of an engine block heater to reduce the warm up time. I don't know about the availability of one for the FEH, but there is one available from Canada (its really cold there) for the Prius.

JeffD

 

It's only a bit cooler here - like 5 - 10 degrees F, still in the 90's some days.
The MPG guage says that I should be getting 30.5 but, after I entered my last tank of gas into the MPG database, it came out to only 28.

Yes, I'll admit to being super-sensitive to the guages in my FEH. I thought that was standard equipment with any hybrid.

Here's a question that I asked a while back with no response - Could it be the gas I'm using? During my road trip back East I used only BP regular unleaded. The moment my FEH began consuming it the MPG started to improve - Very, very quickly. BP is not available in the Houston area and the last tank I used was Chevron. Could it be the gas I'm using?

 

Yes, the gas formulation does make a difference. E10 (10% ethanol) has about 3% less energy content than 100% gasoline and 'Winter" formulation gasoline has less energy content than 'Summer' formulation gasoline (The Butane is removed since it tends to stay liquid at low temperatures and your ICE wants the fuel to vaporize for combustion).

JeffD

 

So, what type of gas should I be looking for? one that has a lower ethanol content? If there is a difference among companies - are there some who supply gas that works better in hybrids?

 

You're generally stuck with E10 and winter formulation (in the winter) as they are mandated by law (Ethanol replaces the earlier mandated MTBE which turned out to be a major polutant of ground water - and a carcinogen). Relax, these issues affect all cars equally, not just hybrids.

JeffD

 

YUCK!!!
So, using MTBE to get better MPG defeats the purpose of driving a green car? I don't feel so bad about seeing my average decrease.
Thanks for clearing all that up.

 

1. 28mpg isn't that bad in city driving. If I spend too much time in stop and go city traffic I'll be running at 28mpg....25mpg with the AC on. The best thing you can do is try changing your routes. I found that a jump on the highway first thing in the morning is more efficient for me than sitting at red lights while the engine warms up.

2. Also, don't trust the MPG display in your vehicle. For some reason its calculations are off. Even when I have 2-3 straight tanks displaying at 31-32mpg, when I do the calculations by hand my average is really in the 29 range. There is a thread on it here:
https://www.greenhybrid.com/discuss/...pump.9761.html

 

MTBE also reduced gas mileage, but not quite as much as Ethanol. MTBE also was produced from crude oil, whereas Ethanol is (mostly) produced from renewable resources.

I say this in spite of the fact that my reasons for originally purchasing my Prius were primarily that I'm cheap (MPG) and I'm a Techie (Electrical Engineering Professor).

JeffD

 

Did you have your oil changed recently?

In the Prius community we've found overfilled oil pans hurt fuel economy, a lot.

Check your environmental controls? Is it possible you're on 'defrost' which can result in stealthy AC operation and hit fuel economy.

Are you using a slow, warm-up route in the morning versus hitting the cross-town expressway?

Just some random thoughts from the Prius community that may not apply.

Bob Wilson