Premium Gas???

[steffen707]

Not sure how this correlates, but when i use 87 octane my mpguino displays about 3-4mpg higher than what I calculate from odometer and pumped gallons, than when i use the 91 octane no ethanol added from the same gas station.

When i use the 91 octane stuff, the mpguino is basically dead on with odometer and gallons at pump calculations.

Anyways, i use the non-ethanol stuff because i've noticed the ethanol stuff screws up small engines, and i get 3-4mpg more from the more expensive stuff.

[Rokeby]

Some posters have said that when they used premium/high octane, >87,
fuel in a car requiring only 87 octane, they got better MPGs. Others have
said the opposite.

Can both camps be correct? Apparently so.

Most sites that discuss premium vs, regular gas are silent on this matter,
But thankfully not Click & Clack, The Tappet Brothers:

Finally, here's a nice irony: to increase gas' octane rating, companies add
ethanol, when they're mixing up a batch of premium fuel. Interestingly,
ethanol actually contains less energy than untreated gas, so the net result
from the ethanol component is a reduction in your MPG. Other premium
additives, however, have the reverse effect, and slightly increase your MPG.
So okay, overall premium provides a very slight net increase in MPG, but it's
so slight that we swear you won't notice the difference.

It would appear that just as when buying regular gas, finding premium
grade gas without ethanol could result in slightly higher MPGs.

FWIW, I'd bet dollars to donuts that ethanol is the cheaper/est of the
additives used to achieve post-refined premium level octane readings.

From Wiki: Antiknock additives
Most countries have phased out leaded fuel. Different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).

[steffen707]

Originally Posted by Rokeby

FWIW, I'd bet dollars to donuts that ethanol is the cheaper/est of the
additives used to achieve post-refined premium level octane readings.

I could be wrong, but when the sign at the pump says, "no ethanol added", I would assume that no ethanol was added to achieve the higher octane rating.

[Rokeby]

I wholeheartedly agree.

And now we, or at least I, know two new things about premium vs. regular:
1. Why all premium grade gasolines are not ethanol free, and
2. When used in premium grade gasolines, ethanol functions as an octane
booster, and not as a tailpipe emissions reducer as when used in regular
grade gasoline.

However, there is at least one new question that comes from all this:

What percentage of ethanol is added when used as an octane booster?

[steffen707]

There is a gas station in my city that has 89 octane with no ethanol added, I should try that. Also i've only used the 91 premium no ethanol added gas from kwik trip as its right next to my house. But the Shell station has 93 premium with no ethanol added and I should try a tank of that too.

Trouble is with my d15z1 swap, I get like 500 miles to a tank. It will be some time before I have to fill up.

[RH77]

I need to run Premium in both Acuras (the TSX for sure due to factory design, and the Integra due to mods -- the fuel savings outweigh the upcharge). Not having that efficiency reduction with ethanol would be nice. (I wonder what they do for Winter blends???)

Anyway, pure-gas.org has a listing of non-Ethanol fuel stations available by State, with the option to add new locations -- and looks to be legit.

Note that some States do not require Ethanol labeling (including my home area of Missouri and Kansas -- so self testing would have to occur). The Site gives details and instructions for the entire determination process.

Best FE,

-RH77

[Ladogaboy]

This topic actually comes up a lot with my family of cars (requires 91 octane). The car has a knock sensor and will retard the engine if the octane isn't adequate. However, as has been stated earlier, the question is whether increased engine wear and damage will result from not using fuel with the octane level that the engine is tuned to run on.

Regardless, I think people also tend to forget the most pertinent detail in this situation. @ ~ $4.00 per gallon for premium versus ~ $3.80 per gallon for regular, the difference in price is only $0.20, or roughly 5% cost savings. Basically, $4.00 on a 20 gallon tank. So, as long as you are not worried about potential engine damage and the switch to regular gasoline does not result in a measurable decrease in fuel economy, it *might* be worth it to use regular instead of premium.

[99LeCouch]

Any engine damage will cost more. And, the difference in performance on a turbocharged or high-compression naturally-aspirated engine might well be worth the premium.

Another difference is that the systems designed to prevent damage are reactive instead of proactive. Sure the knock sensor will cut timing, but engine damage might already have occurred from the knock it sensed.

Using premium in a car that calls for it is a proactive way to prevent damage.

[blownb310]

Has anyone here purchased the Fuel Testers kit and checked to see if the ethanol free fuel they buy is really ethanol free?

Mike