Where I live, an 89 octane blend of ethanol is 20 cents cheaper than premium and 10 cents cheaper than regular unleaded.

However, I've heard that ethanol fuel produces worse gas mileage.

Does anyone have experience with putting ethanol in their RX8? Any performance issues? Major changes in mileage?

 

Make sure you read the owners manual caution on using fuel containing ethanol. It says in part:

"Your vehicle can only use oxygenated fuels containing no more than 10% ethanol by volume. Damage to your vehicle may occur when ethanol exceeds this recommendation, or if the gasoline contains any methanol."

As to your specific questions, I have no idea. However, don't be penny wise and dollar foolish, if you get my drift.

 

All fuels that use ethanol will give you lower MPG because the energy content is lower than gasoline. Correct me someone if I'm wrong but I think ethanol has 40% of the energy by volume than gasoline. This also means you need more of it to produce the same amount of power, which could cause you to reach a limit to what your injectors could inject.

 

Here in Chicago, that's all they sell at all grades is Ethanol blend gas.

The issue with ethanol blend gas is that it contains less energy content per gallon than straight gas.

No performance issues that I see, but replacing 10% of the gasoline with an ingredient that produces 45% fewer BTUs causes a decrease in fuel mileage of about 7-10% depending on the car, environmental factors, etc.

A pound of straight gasoline has between 18000 and 19500 BTUs (British Thermal Units - a measure of the amount of energy input required to raise the temperature of one pound of water by one degree Celcius), but straight ethanol has about 40-45% less - 11500 BTUs per pound of Ethanol (Gasoline weighs about 6.25 lbs/gallon, by the way). A blend of 9 lbs of gasoline at 19,000 BTUs/lb. (171,000 BTUs) and 1 lb. of Ethanol (11,500 BTUs), yields a fluid that carries a total BTU content for its 10 lbs of 182,500 BTUs. 10 gallons of straight gas would contain 190,000 BTUs of energy.

The energy content is what allows the combustion of fuel to do work - push rotors, or pistons, heat liquid, etc.

The more thermally efficient the engine, the less this problem is amplified, and the LESS thermally efficient the engine (as in the more fuel it wastes in the form of heat rather than in generating kinetic energy), the more this problem is amplified.

So, the LONG WINDED answer is yes, using Ethanol has an effect on fuel mileage in your -8. I notice about a 7-10-% increase in mileage when I can burn a tank of non-ethanol gas. I've never noticed any driveability issues.

And that's your physics and chemistry lesson for today, boys and girls.

Stew

 

It is tempting to want to use the cheaper pump, but I think I may just stick with premium or regular.

Although I feel bad since I live in Iowa and ethanol use helps support local farmers!

 

at 10 cents a gallon less (by the way, my mom lives in Newton, so I drive through there a lot. Gotta love Whitey's Ice Cream!), and at the current price of gas, the "cheaper" (it's actaully more expensive to produce but the marketer charges lower taxes on it, so you pay less at the pump) ethanol blend gas is actaully a waste of money. When it was a deal is when it was close to a dime less at a per-gallon price of $1.40! Then it was a deal. Now it's just a ripoff.

I just burn 87 octane regular and it works just ducky for me.

 

Don't forget that ethanol is an oxidising agent and will attempt to eat anything rubber or plastic it can get near ... I wouldn't risk damaging your car just because the farmers need government help to prop up their unsustainable farms.

 

Are manufacturers still using materials that are incompatible with E10? I thought that stopped being an issue over a decade ago.

 

MN Requires E10 statewide, with an exception for small engines and classic autos (very few gas stations sell fuel w/o ethanol!)

The only damage E10 (or less) will do to your RX-8 is lower the fuel milage and the power. Personally I try to find real fuel and put it in my 8. My other vehicles I use the cheapest fuel I can, wherever I am.

(Stay away from E85 though unless your vehicle is setup for it... around here E85 is the cheapest fuel by far...)

 

Agree, E10 is harmless except to your fuel mileage.

 

20 Cents cheaper than premium, and brings out so much problem... how much more is it? 0.2cent x 15.9gallon = $3.18, 4 times a month, that's $12.72. I rather feed my beauty better stuff then save $12.72 a month... even my cable is more expensive....

 

Some of us don't have that choice. Like Fray in MN, I can only buy E10 here in Chicago. have to be 150 miles out in the sticks before real gas becomes available again.

 

This is the Mazda Australian position on Ethanol :

http://www.mazda.com.au/articleZone1...8#Article-2087

They do agree that the rx8 is "suitable" for E10, but ...

Issues which can arise as a result of ethanol being used in non-suitable vehicles

* There is an increased possibility for the metal fuel tanks and lines to corrode or rust.
* There is an increased possibility for plastic fuel tanks to swell and break down.
* There is a possibility for plastic and rubber fuel lines to deteriorate.
* There is a possibility for fuel injector o-rings to break down.
* Carburettor floats and seals are susceptible to deterioration.
* Certain engine components may not be compatible.
* Engine management mapping parameters may not be entirely compatible with E10, thereby creating idle and driveability concerns, starting concerns and hot weather performance issues.

Points to note

* Ethanol is an oxygenated fuel. E10 (which is oxygenated gasoline) may reduce fuel economy by an average of 2 – 3% because oxygenates contain less energy than non-oxygenated petrol. As such, there may be fewer kilometres per tank of fuel when using E10.
* Ethanol has a high affinity for water. Therefore, ingress of water could result in ethanol blends of petrol to break down into separate water/ethanol and petrol layers. This could create driveability concerns as there is the possibility of water/ethanol slugs reaching the engine.


* In some older vehicles, deposits in fuel systems can be loosened by E10 which may cause fuel filters to become blocked.
* Coarse ethanol, which is of poor quality (like ordinary fuels of poor quality), may cause poor idle, derivability concerns and starting issues, even if the vehicle is suitable to operate on E10.

 

Well .... considering that Illinois has had this mandate now for 10 years, and I have yet to see any issues with it, I'd say ... OK, cautionary, but in real practice, no real damage.

That said, the fuel economy "damage" is quite real and quite worse than stated here.

stew

 

I agree with StewC625. The only damage w/ Ethanol is fuel economy.. and my butt Dyno says a bit less power as well.

Use E10 when you are driving to work.. use real fuel when you are on the track or need extra power.. (Since my 8 is not a daily driver.. I try to keep it full on real fuel..)

 

Wish I could do that without driving 150 miles or to another state.

 

My suggestion, look for collector car clubs/hot rod clubs. They may have pointers on buying non-oxygenated fuel in your area.

 

I just drove past a Gas City on the way home and just about crashed the car. They actually had E15 Ethanol on the price sign. And it was $2.35 p/g. That's 40 cents cheaper than current 87 octane prices!!!!! Where'd this stuff come from? Never seen E15 before.