90 octane over the ethanol 87 octane will be a slight to negitable increase in performance, but no ethanol over 10% ethanol will net about a 10% increase in fuel economy. Just my opinion ofcourse. I have found it to be true in our old cars, but little to no difference in the computer/efi systems of today.
That may well be your opinion - but it isn't actually what's happening.
There's documentation and written articles all over the web on this subject, of course - but the undeniable
facts are that "straight" gas has around 125,000BTU of energy in a gallon (mid-grade octane) and pure ethanol
has about 75,000BTU.
A mixture of the two (for example, the 10% ethanol blend they do around here) yields around 110,000BTU - and
less energy/"food" (BTU) per gallon is going to mean less fuel economy in the same application, every time.
Doesn't matter if it's an old car or a new one, that's always going to be the case.
Of course, another natural byproduct of that higher BTU content is more power possible from that same gallon
as well.
Yes, computer cars of today can adjust and maximize the optimum use of different fuels on the fly
a whole lot easier, but the fact still remains you get less potential
Work from the same amount of
Fuel
with ethanol blends vs. pure gasoline of similar octanes.
All the maladies associated with ethanol usage in old cars is a whole 'nother kettle of fish I won't get into
here (also well known, well documented, etc. out there)...but there's only one reason ethanol blend gas
is generally cheaper at the pump than 100% gas is:
Government subsidies.
Not at the pump so much, but at the production end of things.
Ethanol costs substantially more to produce than gasoline does initially, after all - but with all the government
subsidies in place (not to mention, the government mandates on the corn-producing industry), the end result
is it takes government monkeying with the market in order to make ethanol cheaper to use.
Yes, that's all by intent, of course.
I also am not going to address the "reasons" government is so heavy-handed into the fuel business (enviro-,
sustainability, tree hugging and all that other kumbaya stuff versus the higher prices of our food in stores due
to what those same mandates have done to the supply chain) - everyone has their own opinions on such
and anyone has zero % chance of changing my mind on any of it.
Personally, I use non-ethanol gas in everything I have that needs gas. Fred the GTX runs
noticeably worse
on the ethanol blend and I've had to replace the old style (but newer) "rubber" fuel lines on him with line
made for use with fuel injection (and the local box auto parts stores still have the old type on reels as well, so
watch out!); my chainsaw and weedwacker have both had to get new carbs because ethanol ate the plastic
parts in the old ones (the local co-op mechanic gave me the heads up about it, since the 2-cycle oil you mix
in their fuel does NOT stop this from happening).
The late model vehicles I'm not as concerned about, as the trade-off in 10%+ less fuel economy (I keep logs)
is compared to the higher price of pure gas - but around town, they get the pure stuff too and within a 1/4
tank, they noticeably have more power as well.
So...
"Straight" gas is the superior product per gallon - but with all the monkeying around with pricing going on,
if all one is concerned about is cash outlay, your own conclusions may vary.
