87 Octane Ethanol Free or 90 Octane Ethanol Free??
 

Not about the dollars, all about the numbers. Gotta get those MPG numbers up.

I'm driving a 2000 Insight with LTO conversion.

So Ethanol Free >> Ethanol for the MPG numbers, but which octane should I be buying? Some gas stations near me have 90 others have 87.

On my fuel log I track the gas type used. That's the 2020 log, you can find my older log (Pre-Lithium) in there as well.

In theory if you can find non-oxygenated ethanol free in a lower octane it should give the best fuel economy. (I’ve only seen it in MN)

Historically there were some comments that the Insight required higher octane overseas but generally 87 has more energy content.

Not sure which would win out, I guess if money is no object throw in some 0w16 oil and dose the tank with some MMO and run a separate tank of each.
I’m leaning toward 90 winning but only by a hair

Will be interesting to see your results.

I have 0W-16 in the engine, what is MMO?

It's hard to get conclusive fuel tank results because of factors like weather and traffic. My tanks vary greatly. Random things like, did I forget to activate my clutch switch on the high way (to keep it from regening in lean burn if the SoC gets low) a couple times, have very large effects.

Marvel Mystery Oil

To my knowledge 90 should not make any more power unless the ECU can specifically detect it and adjust ignition timing for it.

Typically engines with high compression can have knock when above ~80% load, and the Insight has pretty high compression. It also has a knock sensor. If the sensor detects knock, it'll pull a few degrees of timing, which affects both power and fuel economy. I believe any knock detected also throws a CEL but I'm not certain if there's a threshold (above zero) for that. But, typically, an engine will not knock on the octane it's rated to have, and if it's not knocking, and the ECU isn't pulling timing to get rid of the knock, higher octane shouldn't help economy because it only really provides more resistance to knock.

How is the LTO conversion?

since it has VVT buy the highest octane you can afford you will be able to pull a higher timing on it

with 87 i barely get 18.5/18.5

91 octane 23/31.2mpg it's able to pull a tight timing of upto 42 degrees advancement with it

it's normally around 27-35 degrees on average

with 87 oct 12.5 degrees advancement is where it tops out at retards the timing in AFM mode to about -2 to -12 degrees it would also rapid flip flop between v8 and v4 (sure that can;t be good for the engine)

it's more likely to search for gears with 87 octane

Variable Valve Timing (VVT) is not ignition timing (spark plug timing). VVT would not indicate an engine's ability to benefit from higher octane, and would not allow changing any variables affected by higher octane.

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Octane (number) is only relevant to compression ratio. (Pre ignition)

The additive package is what’s really relative to any performance gains.

Go to a race track or airfield and buy gas. (110 octane race gas or 130 avgas)

Currently (approximately) around $4-6 per gal.

You’ll see what real gas can do...;)

When I was young and spilled some gas you dare not light a cigarette or create a spark unless you didn’t care about your eyebrows. Now you almost have to hold the flame to it to make it burn.

How things have changed. :(

Petroleum Companies figured out how to extract the chemical compounds in consumer grade fuel for other products (more profit) while leaving the bare amount necessary for ignition in a internal combustion engine.

There is a silver lining with today’s E85 though. One can build a high hp , high compression engine (15 to 1) to easily take advantage of the high Octane number (108) .

Research where your fuel comes from. As there can be noticeable differences. Brand names usually have their own storage tanks (additives) that they pull from but not always. No name gas stations usually get whatever is available through the bulk distributor. (Crap shoot)

Seriously, try some race or avgas and let us know what happens.


:)

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Hate to tell you this but AVGAS is heavily leaded, will clog a cat in one tankfull. Probably the same for race gas, but I'm otherwise qualified.