Sugar free maple syrup?!? that's like saying gum free gum!!!

Or non-alcoholic gin. What's the point? :iono:

sugar free sugar!

Actually, our cars are not "tuned" for 93 octane, or any other octane. Octane requirements are dependent on the engine's compression. Octane in effect raises the temperature at which the fuel mixture will ignite.

We need fuel with a higher octane because our engines are high compression. Higher compression=higher temperature.

Also, the engine's computers don't lower compression when knock sensors detect knock. How could they? Compression is fixed. The ECU changes the engine timing to compensate, based on signals from knock sensors. You'll get less horsepower, but that's just a by-product of the less-than-optimum timing.

Lastly, it doesn't matter if the ECU could detect what octane fuel is put in the tank. What would it do with the information?

Indeed!

I notice this when using super cheap $2.60 91 Oct vs Chevron $3.09 or Shell 91 Oct $3.15.

I spoke with Gas Station owner and he said it's due to the ethanol and lack of additives. I noticed the spark plugs wearing out quicker with 87 oct on friends IS300 when manual said to us 91. Gas station owner said ethanol content was about 20-26% (?).

I always thought ethanol tops in gas was about 10%???

:thumbsup::thumbsup::thumbsup:

And high compression ratiio helps achieving better thermal efficiency of the engine.

[ame="https://www.youtube.com/watch?v=t4yh5Pt8was"]Compression Ratio and Thermal Efficiency - YouTube[/ame]

In other words, the high CR and the need for high octane are some of the costs of squeezing 200 HP form 2 liters.

You're right it reduces timing, not compression, my bad, and that in effect reduces the horsepower.

But what I mean is your ECU can detect fuel octane below factory specifications (or factory "tune") and compensate by reducing timing/power. But putting higher octane than factory specs, will not have the opposite effect. The ECU will not detect higher octane or do anything to take advantage of it.

The ECU doesn't detect octane. It gets a signal from the knock sensor and retards timing. There are a number of causes of knocking. Low octane is one of them.

:thumbsup::thumbsup:

I had to retard my brain timing to read this thread.

Fuel quality is easy to measure. You guys are overthinking shit. It's called a data log.

For the Californians... mixing 91 and 100 is silly. You literally have E85 stations everywhere. Get a flex fuel kit.

I think fuel issues should be a sticky and anyone making a new thread should be deleted IMHO. I'd say this goes for oil and tire threads. :P Happy Bunny Day!

all engines must be designed to run on 87 octane, 2L boxer engine is no different. using 87 octane will do no harm, because it's the rule. The manual says a lot of things to lower the liability of the manufacturer such as touchless wash only, wash after driven on salty road every time, don't mod your car... you get the point

i will have to disagree with you on the E85 stations being everywhere, the nearest one from me is a good 20 miles from me, so a 40 mile trip for it, would not be very economical for me.