Fuel Requirement

I have been using the mid-grade gas since I purchased my 2010 Prius and don't mind that too much. What concerns me now is hearing about a requirement to have 15% ethanol in all the gas. Owners of older cars were counciled to find stations still pumping gas with a lower percentage but I figure that all gas will be 15% eventually. The manual for my 2002 Prius said to not use Gasahol. Will this E15 gas be OK for my Prius? It sounds like I may not have any choice in the future of getting E10 or lower gas.

If I had a flexi-fuel Chevy built for Brazil I would not be concerned, but the gaskets in most cars are not made out of polymers that can stand up to gasahol.

 

Don't use mid grade fuel. It is not required or recommended. Your Prius is designed to use 87 octane regular unleaded. Using higher octane fuel costs more and will likely reduce your mileage.

As for ethanol in your fuel, it's pretty much a fact of life for most of the country. It will cost you a bit in mileage, but there isn't anything you can do about it.

Tom

 

Quite an interesting thread for me to read. The lowest unleaded here is 95 octane then 98 for super and some supers at 100 octane (Shell I think). Our handbook states not to use less than 95 octane but is the same engine and set up as yours.

 

Your octane rating system is not the same as ours. I believe what you are seeing is a combination of higher engine tuning and a different octane rating system.

Tom

 

You sure? It says 95 RON. I thought that was a standard rating.

 

I concur that the use of mid grade fuel is a total waste of money.

Also, almost all cars made in the past several years have gaskets that are proper for use with the level of ethanol which is allowed in gas in the USA. As I understand it, most gas in the USA contains about 10% ethanol. On the other hand, E-85 contains 85% ethanol. Huge difference. Have you seen any verifiable accounts of widespread damage caused by normal gasoline with 10% ethanol in any modern (past few years) automobile?

 

For you, not for us. We use the average of the Research and Method systems.

Tom

 

So how do they compare?

 

There are several rating systems. I don't remember all the details but as I remember it in Europe they use the RON or Research Octane Number and in the USA they NOW use the AKI or Anti Knock Index. Without going back to look this up, I am pretty sure that you can pretty accurately estimate the American octane number by multiplying the European number by .95. So, 100 Octane in Europe is the equivalent of 95 Octane US. Conversely, if you multiply the US octane by 1.055 you will get pretty close to the European (and Japanese) Octane rating.

 

Regular is 87 which is one unit of octane lower than the recommended. The gas I call mid-grade (inbetween regular and premium) is at 92. So should I use regular is that what you are writing?

 

My previous car was a S class MB, I now have a ML 320 MB, both cars call for premium gas, I have always used mid range with no problem, the engine sensors will set the timing for the gas used.
Have a friend who also has a ML that is 10 yrs. old and has always used regular gas with not problem, I am not that brave, I had the S class for 10 yrs. and the ML for 10 and not problems so I don't see why a modern engine like the Prius has will suffer for a one octane point difference.

 

No, 87 is the recommended octane. The 2010 User Manual has an error calling for 88. Toyota has come out and stated that this was a typographical error: 87 is the correct figure.

Tom

 

87 is exactly what is recommended. Some owners manuals had a misprint that said 88. That is wrong. My manual says 87 and so do all of them now.

 

I'll have to look at my manual. Good to hear 87 is ok.

 

It's not only okay, it's recommended. The only exception is at high altitude, where 85 is recommended.

Tom

 

Yesterday on the Clark Howard Show (HLN Network) he reported that the government was going to allow the marketing of 15% ethenol gasoline. He stated that small engines require no more than 10% ... and suggested that owners of small engines (lawn mowers, trimmers, etc)(he also included older gasoline cars) may want to look for dealers continuing to provide 10%.

I suppose that raises a problem for us, especially if the Prius requires no more than 10% ethenol (as reported earlier on this thread). Some of you more savvy writers, how about providing some council on this subject.

I have never burned anything higher than regular grade gasoline in any of my cars. Does the higher grades contain less ethenol? I always thought that ethenol elevated the octane, but cost less and lowered the mpg efficiency. I recall seeing pumps side by side, one w/out ethenol and one with. The "with" pump advertised a higher octane rating, and cost less.

 

Good question, this state will probably require all gasoline to be 15% ethanol rather the feds do or not, at least if our Governor gets his way which he usually does.

The owner's manual pg 570 says up to 10% ethanol, as you mentioned.

I logged on when the Prius Team did its Q and A thing a while back and submitted the question, will Toyota permit us to use 15% ethanol? They, of course, did not accept the question. Actually it looks like if that's all we will have they (Toyota) will have little choice except to OK it for use.

BTW I listen to Clark also, when I can, he has given me some good advice over the years.

 

Oh great, now they're going to raise the scam of ethanol to 15%?

 

E-15 (gasoline with 15% ethanol) will really hurt the small engines. Small engines were made cheaply for light duty (compared to a car) but to last a long time under light use. A snowblower can last 20 years. A mower can last 10 years. An E-15 will eat up gaskets, pumps, fuel lines and even plastic carburetor floats.

Of course, small engine manufacturers would be stupid to make them just for 10% ethanol because then, for whatever reason, if ethanol goes up to 11% or so, the small engine will self destruct. There is probably a safety margin. The question is: what is the margin? and does it go as high as 15%? We won't know until we try or until the small engine manufacture wants to share the data. Of course, your E-15 gas may also have a margin, a manufacturing tolerance, say it is really E-14 to E-16, or E-13 to E-17. So if your small engine has a margin to E-15 but you put in E-17, you will shorten it's life.

As for the Prius, ethanol holds water and sucks moisture out of the air. The moisture rusts the engines, steel fuel lines etc. They don't tell you but 100% ethanol is hard to produce because it is so hydroscopic. The gasoline grade ethanol probably is only 95% or 90% only. So E-10 is probably 90% gas, 9% ethanol, 1% water. The Prius have fewer plastic parts but probably more gaskets and a longer fuel line etc.

Also, you should never change the fuel drastically in a system. That's because there is a buildup of legacy dirt (insolubles) in the system - things that don't dissolve in gasoline or 10% ethanol. This is fine and is to be expected. Everytime you pump gas, you get more insolubles. Now you suddenly change the gas, the insolubles may suddenly become soluble and swamp the system. Maybe the system was designed to handle some dirt and gum. But not 5 years of buildup in one tank. Some of the stuff captured by the fuel filter may start to dissolve.

The sudden burn-off of the now soluble gunk may coat the exhaust. Damaging your catalytic converter.

If it ever come to pass, I suggest you fill up with E-15 a gallon at a time mixed in with old gas to slowly adjust your car to the new gas.

For those of us who drive late model cars, it may not be a big problem because car manufactures will adjust. I drive late model cars not because I am rich, but because I drive a lot and wear them out fast.

 

Oh drat, oh well, I will go back to buying the cheapest gas. A typo!!! cost me money. The main gripe was that Costco did not sell the mid-grade gas so I was buying the high octane stuff. Back to buying the cheap stuff.