Pro-ethanol measure affect on Prius Gas Milage ?

Depends on where you live:

Personally, I've noticed no measurable difference between E10, Regular, and Premium fuels.

USA Manual:


Australia Manual:

 

some say the mileage is affected by the same percent as ethanol. we don't have non ethanol available to test

 

I generally use non-ethanol. In previous cars, I've had up to 10% worse consumption, and up to 10% better with PREMIUM - both of which rule them un-economical.

In response to someone a few months ago suggesting that they got amazing economy with PREMIUM, I put 2 tanks of PREMIUM through recently - exactly the same l/100km. That's $1.93 instead of $1.70/litre. Certainly not worth it - apart from possibly cleaning injectors, throttle body etc - maybe. It definitely had more power - if I used my imagination boldly.

I also filled up a while back where they only had E10 - and it didn't make any difference, I went back for a 2nd tank, and I couldn't detect any difference. But it's only 2c/litre cheaper - so I use the real thing.

 

E10 contains 3% less energy so 3% less MPG so you see 48.5 MPG vs. 50 MPG, all things equal.
E15 contains about 4.5% less energy so you see about 47.8 MPG vs. 50 MPG

Now to really say that, we would need EPA test data on the ethanol blends, for each vehcile. which nobody seems interested in doing that testing. So EPA uses E0 and makes the mathematical corrections per above to adjust results for expected fuels.

 

I'm trying to get my head around - if my trip shows 43% EV - how will that affect the "... 3% less energy ..."?

 

Not sure, but if you are not plugging in, that's what we would expect short of doing lab testing in a controlled test. We as consumers (not insiders at Toyota) have no rule-of-thumb that says Prius is different on the normal EPA/industry adjustment equations, which basically say that MPG is proportional to gasoline energy content, which energy content is something that can be measured for test fuels.

 

I've logged every fuel fill since March 1974, with spreadsheets since about 1991. With some previous cars, there was almost no differences between fuels. Others were distinct.

My VOLVOs (244 and 940), Datsuns, Mazdas from the '70s-'90s had a noticeable hit to economy with E10. But they showed almost no improvement with PREMIUM.

My 2006 KIA was the first with CVVT and a knock sensor - and E10 affected it slightly worse, but PREMIUM gave a measurably improvement (but not enough to counter the higher $$).

Then 2 FORD Diesels - which wouldn't run on bio-diesel - ran OK, but trouble starting. I soon discovered that the Manual said "DON'T".

Then PRIUS. It's an odd car to track what it's doing with economy. I drove 150km, mostly motorway, yesterday, it showed 24% EV, and got 3.5 l/100km (67USMPG). If I'd driven a similar sized hatchback, I'd have used about twice the fuel - with 0% EV. The efficiency of PRIUS is playing tricks here somewhere.

 

Keep in mind each Country has their own gasoline formulation things going on. Here in USA, many Prii are running on reformulated gasoline, which is quite constant energy content between grades because EPA fixes the recipe, and its all E10, and we cannot get anything else in those areas. You probably have some juicy energy content fuels compared to us, but I am less familiar with OZ fuels. But you probably have more energy variations than we have too.

 

I'm presently trying a tank of ETOH-free here in Florida. The station that sells it offers it only in mid-grade (89). After I filled up, I noticed that it's not Top Tier, which of course, Toyota strongly recommends. It's also $2.99 per gallon (edit -- that's roughly $0.50 more than the E10), so unless it provides a really strong improvement over the vanilla E10 regular (87) which IS Top Tier, I probably won't mess with it again.

How observable it is, I don't know, but mileage certainly should decrease as the amount of ETOH in the fuel increases. ETOH is less "energy dense", so for the same output, you have to burn more of it. Next tank for me will be E10 and I'll see how it works.

 

If it was me, I'd be sampling for some data.
I've done this quite a bit (prior posts), I would be measuring the density of the E0. The way I would do this is fill my plastic gaso can with exactly 1.5 gals of E0 and then I have a scale at home to measure the grams and then I can get grams per cc.

Here in Reformulated Gasoline territory, in so many words, density is limited by EPA to about 0.74 g/cc. EPA does not actually regulatate density, but that is the net effect. So if you saw something like 0.78 that would be 0.78/0.74 or about 5% + 3% = maybe 8% better MPG than the E10 RFG gaso that I am forced to use. The plot thickens for you however, because you have to also estimate the density of the E10 alternative case, which is also probably better than my RFG stuff.

However, it strikes me that non-TopTier, non-RFG 89 Octane E0 gaso could possibly be energetically/MPG juicy as well. So you could alternate fill-ups or add some of your own Techron to make your own TopTier.

The only reason I do not do more study is because I live in RFG area where E0 is unavailable and there is not variation in energy content between grade. So my work here is done unless I move to rural Virginia.

 

I would love to delve into this some more, but practical reality overrules. My home, my garage and all my tools and things are up in Pensacola. I'm presently living out of a suitcase down in Vero Beach (eight hours drive away) doing training, and I'll be here several more months at a minimum.