Is there a recommended gas for Prius?

Some of us go out of our way to buy 100% gas. See E85 Boondoggle of the Day: TTAC Prius Driver Says Ethanol Sucks

Ethanol-free gas stations in the U.S. and Canada is a good way to keep track of stations that offer it.

 

Yes 100% gas is probably better, unfortunately as Alfon mentioned in Oregon we can only get E10. I always use 87 octane around home, when I travel to the mountain states where elevations are higher I use 85 octane when it's available.

Brands, I fill up at Costco when I am near there. When I travel I usually pick Chevron or Shell. I try to find stations that are clean and look like they do a lot of business.

 

Tom

 

All I ever use is E89, and I have had no problems. I am averaging 51mpg right now.

 

Scott, did you mean E89 which would be 89% ethanol or 89 octane?

If you are using 89 octane you might consider trying a few tanks of 87 octane. Some of the petroleum experts who have posted on here (not me) have said that regular gasoline usually contains more energy than premium. The only advantage to a higher octane would be that it has more resistance to pinging or pre-ignition.

 

Very interesting link on the E85 Boondoggle. The lack of intelligence of this guy on the link is amazing. First off, he's running 10% ethanol, not 15% like the title says. Then he calculates his new mileage with only 130 miles. There is a huge margin of error when you only fill with 4 gallons. Just the difference of where the pumps click off could make up to a 15% change. It's just not scientific. But of course that would ruin his rant. Then to think that 10% ethanol will decrease your mileage by over 30% like he is claiming. WHAT? Even if the 10% had NO heating value, he would only kill his mileage by 10%. But ethanol has around 60%, so the decrease for 10% ethanol will be 4%. Or lower your mileage from 44 mpg, down to 42.2 mpg. And that to me is worth it to have a cleaner atmosphere.

 

Thrifty or U.S.A. gas is what my baby seems to prefer.

 

The OP needs to read his Owner's Manual. It's full of stuff like that he needs to know.

89 octane is a complete waste of money in a Prius. It simply isn't needed. If the engine pings it needs repair, not a higher octane fuel.

 

the kind that burns and comes out of a pump, regular grade and preferably from a busy station is all you need to know

 

doesn't matter, stick with anything that is a brand, so you have some, assurance of quality, and try to use a busier station over a slower one that is it

seems hard, neigh impossible to believe that only one particular manufacturer would have a problem with only one particular gas brand.

yes the gas is typically transported thru shared pipelines for the most part, for long distance transport. But no the special sauce isn't added at the station, any brand specific additives are going to be added at the distribution location, prior to shipping to the local station. You really think they have the equipment to mix a volatile substance at a local gas station? That Exxon, Shell, Chevron, et al are going to trust some minimum wage guy/gal to calculate correctly how much of something to mix in and do it correctly on a regular basis, daily, across hundred or even thousands of stations?

I have used it for years, in multiple vehicles, 4's, 6's, 8's, twins in V shaped engines, in-line engines and in opposed engines. German, Japanese, English and US manufactured vehicles. There has never been a gas related problem. 100,000's of thousands of miles all told. While I don't limit myself to one brand, Costco gas is my most frequent brand, probly accounting for roughly 60% of my gas purchases.

Hard to beleive Costco gas was at fault, since they aren't beholden to one distributer. Detonation usually is a problem with too low an Octane.

 

Also the fact that it was about one incident of "bad" gas getting out, and in a limited area of the country and didn't seem directed at one brand of vehicle.

but it is on the web, it must be true...

Yeup, 4 gallons, by the automatic shut off no -less, not actually a measured 4 gallons with a person driving over public roads, yeah, and you are saying that is not scientific? Really?

 

Yes, I suspect he means 89 octane E10.

I will argue the point that a Prius can benifit from higher octane fuel, it is an Atkinson cycle engine that can adjust it's its cylinder pressure to be as high as possible within the detonation limits of the fuel.
The higher the cylinder pressure, the more efficiency an engine can can get from a gallon of fuel. The Prius 1.8 engine has a mechanical compression ratio of 13/1, so it is capable of gaining conversion efficiency from higher octane fuel. it uses a knock sensor to detect detonation and adjusts cylinder pressure Via the Atkinson system variable cam timing and adjusts ignition timing to wring the most energy out of the fuel, just short of detonation.
Granted, the Atkinson system will detune the engine to run even poor quality 87 octane fuel, but conversion efficiency will suffer a bit with the lower octane fuel.

That fellow in the link above that claims huge MPG drop with a Prius burning a 10% Ethanol blend, does not let reality get in the way of a good hate story.

Pure 100% Ethanol has 30% less heat energy that pure 100% gasoline, so a E10 blend that is 10% Ethanol and 90% gasoline has 3% less heat energy because of the 10% ethanol content.

At most, this will drop fuel economy 3% in an engine that can not take advantage of the greater conversion efficiency higher octane fuel allows.

In the case of my 2010 Prius, in my experiments with my Prius on the fuel blends avalible locally , I ran 3 tanks each of(aprox 1500 miles per fuel type) of 87 octane regular, 90 octane E10, and 91 octane premium.

My best mpg of all three fuels was hands down best (by 1-2 mpg) was E10 blended from the same quality 87 octane gasoline base stock mixed with 10% Ethanol.

I live in the north where I have to deal with sub freezing temps for 5 months per year, where fuel system freezing is a problem unless you use a "heat or dry gas " type moisture removing gasoline additive or use E10 which does the same thing with the 10% alcohol content.
Another advantage is that ethanol is a great fuel system cleaner and prevents / removes gasoline gum and varnish deposits from the entire fuel system.

I have used E10 for 30 + years with great results, ( since the days when they called it gasohol.

I also roll my eyes whenever I hear the old lie that it takes more btu's of Hydrocarbon energy to produce Ethanol than you get out of it.

The latest Dept of agriculture research states that for each 1 BTU of diesel and natural gas used to produce fertilizer, grow, transport and convert the crop to ethanol , you get 2.3 btu of ethanol energy plus you get back 17 pounds of DDG (per 60 pounds grain input)which is a great livestock feed.
That 2.3 btu return for each 1 btu invested , means we have an extra 1.3 btu of sunlight converted to liquid fuel to run our cars.
A clean renuable fuel that cost no lives in the middle east.

 

It seems to me that my 2003 prius runs better on the non-ethanol stuff...after I studied out a potential reason i came to the conclusion-my year model did not have flex-fuel technology. Possible?

 

I would be surprised if there are less than 10,000 such threads on the internet discussing which octane of gas to use, whether we should use name brand or not, talk of moisture in little-used tanks, etc.

And in at least a thousand of them I've said I get the cheapest gas I can find that meets octane rating specified in manual. In this case I get the cheapest 87 I can find. It's all the same.

 

This would be true if the Prius engine could adjust the intake valve timing to adjust for octane, but it lacks the sophistication to do that. All it can do is retard ignition timing if knock is detected, but under normal conditions regular gas will not produce knock given the standard compression of the Prius engine.

The 13/1 compression ratio refers to the power stroke expansion ratio. The compression ratio is considerably lower. Granted, it could be that high if the intake valve timing were changed, but then you would have an Otto cycle engine that would require very high octane fuel, or a low compression diesel engine.

Tom

 

Possible, although my 2010 is also non flex fuel.
You really do not need flex fuel for E10, while you would for E30 or E85.

E10 is not only accepted , but , it's use is encouraged in the 2010 Prius OP manual.

It may also be that the 2003 fuel system calobration is not the same as a 2010, which may be part of why your Prius does not like E10.
Also, all E10 is not the same quality, the companyI buy fuel from uses their same good quality 87 octane gasoline stock to blend with various amounts of E 85 to produce E10 , E30 or E85 from the same blender pump.
I have read that some suppliers use a poor quality, low octane gasoline stock, then mix it with more than the indicated 10% Ethanol to bring the octane up to an acceptable 87. This stuff will not do as well as E10 made using a higher quality gasoline stock.

If you wish to experiment, try using different brands of E10, especially those from a company using blender pumps. They like to keep things cheap and simple, so they have a tank of regular, a tank of E 85 and a tank of premium conected to one blender pump, and blend various amounts of regular and E85 to produce E10, E30, E85.. This limits their ability to use a very crappy grade of gasoline stock to blend their E10.

 

I disagree, my Prius has an Atkinson cycle engine that controls cylinder pressure via a variable intake cam timing system.

If the knock sensor senses detonation, it retards the intake cam timing / closing of the intake valves to allow part of the intake air charge to blow back into the intake manifold, giving the cylinder less air to compress, thus dropping the cylinder pressure just below where the avalible fuel will detonate.
The mechanical compression ratio of the engine is 13/1 as stated in the OP manual, but cylinder pressure is reduced by the intake cam retard system (Atkinson cycle) to allow the use of lower octane fuel at wide open throttle, yet maintain maximum possible cylinder pressure at part throttle for best fuel economy.

 

Variable intake cams were added for the Gen III Prius, and they do provide some adjustment of the compression ratio, although it is still very limited. The variable valve timing was designed to increase efficiency by reducing the need to drag air across a closed throttle plate. It wasn't designed to take advantage of high octane fuel. Certainly you could do that with variable intake timing, but I don't believe this was done with the Gen III Prius.

Some newer designs are being tested in the labs which improve on this idea to the point where throttles are not needed.

As you point out, the Prius engine simulates the Atkinson cycle by delaying the closure of the intake valves. As we all know, a real Atkinson cycle engine has a unique crankshaft design that allows for differing compression and power strokes. However, it has now become common to refer to the modified Otto cycle engine in the Prius as an Atkinson cycle.

You can call the 13:1 ratio a "mechanical compression ratio", but that is a bit disingenuous, as the engine never uses the full stroke for compression. The 13:1 is really an expansion ratio.

Tom

 

It depends on which generation Prius you drive, if your Prius is a generation 3, the operators manual says on page 105, the recommended fuel is 88 octane OR HIGHER.

The gen 3 Prius 1.8 engine is designed to take advantage of higher octane fuel.
my 2010 Prius gets 1-2 mpg more using 90 octane E10 compared to 87 octane regular.

 

It depends on the generation Prius you drive,
The operators manual for my 2010 Prius generation 3 , on page 105, recommends 88 octane OR HIGHER.

It makes a difference on fuel economy. My 2010 Prius makes 1-2 mpg better on 90 octane E10, as compared to 87 octane regular.

The beauty of it is that "here" , 90 octane E10 is 5 cents a gallon cheaper than 87 octane regular, plus it eliminates the need for an anti icing additive in winter