So I haven't seen an answer here, and I'm hoping someone will be able to tell me.

I've read about 87 vs. 91 octane, that 91 is a waste of money if your car can run 87, but my question is regarding ethonal and gas.

In MN all gas is required to be 10% ethonal. As most people know ethonal cuts down on CO emissions (increases CO2) and allows a more complete burn of the fuel. (but you lose some power)

However, we do have a handful of stations in MN that sell non-oxygenated gas (no ethonal). Is it worth buying 91 octane that is pure gas instead of 87 octane that contains ethonal? I'm having a hard time finding out what ethonal really does in an engine/rotary.

 

Ethanonl has less BTU than gasoline, but a higher octane of like 106.

If the gas is rated for 87 and has ethanol, I would think you would get a higher chance of detonation, and less power...

 

dont you mean less chance of detonation, as higher octane fuel burns slower so less detonation.

also if i remember correctly, the OWNERS MANUAL states that mazda does not recommend and ethanol blended fuel for the rx-8

 

Doesn't recommend over 10%, which is what the state is currently at. Technically the non-oxy gas isn't even supposed to be sold for cars unless they're antiques.

 

No ethanol does not necessarily mean non-oxygenated. Could be using MTBE (methyl tertiary-butyl ether) instead.

 

The gas is sold specifically as non-oxy, and is labeled as such at the pump.

 

Ethanol contains about 70 to 75% the energy of gas so if you have a fuel mixture with 10% ethanol you can expect a reduction in power and mileage of about 2.5 to 3% using this mixture.

Methanol is worst at around 65% the energy content.

The new E85 fuel you hear about has about 72% the energy contain of gas so you'd be looking at a reduction in power and fuel economy of 28%. This stuff is crap.