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Originally Posted by forpinks

Also the 106HP (not high performance? I know.) is achieved using high grade high octane gasoline for testing (Since Japan don't have anything lower than 93 octane they even have 120-125 octane) the engine power will drop to 100flywheel HP when you use 87 gas and it will make more gunk to the engine because of the slight combustion difference even with the knock sensors, remember the 1NZ-FE is japan made and tested so It should run 90+octane and will get 51MPG elsewhere except US (may be possible with acetone) which don't have anything higher than 93 basic fuel 100 octane cost like 4.30 vs 3.30 91...

The rest of the world measures octane different than us in North America. In the EU and Australia, they advertise RON. Here we use an average of RON and MON. MON is a lower number than RON. YOU CAN'T COMPARE OCTANE RATINGS BETWEEN NORTH AMERICA AND THE REST OF THE WORLD.

The ignorance in this thread makes my head hurt.

Octane only measures the autoignition characteristics of gasoline. How easily it will explode without a spark.

THE ONLY THING THAT WILL CAUSE MPG TO INCREASE ARE O2 READINGS.

If the O2 sensor reads the car running rich, it'll lean it out within safe parameters. Lean = less fuel used = higher MPG.

HIGHER OCTANE DOES NOT CHANGE THE AIR-FUEL MIXTURE.

Higher octane gasoline can only prevent detonation. If your detonating with 87 octane, something is wrong with your engine/ECU.

A car runs a base timing and advances or retards it only within set parameters. And those parameters are ones set by Toyota Engineers as to be safe with low octane gasoline. The computer will not exceed those if you put high octane gas in and magically the computer knows.

Besides, there is no sensor that can tell what octane is used. To measure octane, you have to find out the percentage of volume is iso-octane and the percentage of volume is heptane. NO production car has the ability to do that...

And anyway, advancing timing does not cause less fuel to be used. It cause more power to be made from the fuel.

Everything else in this thread is anecdotal evidence. There are many, many, many variables. Elevation, wind, drag, tires, air pressure, surface type, load, weight, etc. The most important thing is repeatability. If you REALLY want to prove higher mileage, rent a couple weeks of dyno time in a lab. Control all the environmental variables to be constant for the whole week (temp, humidity, air flow, tire pressures). Empty the car 100% of all gasoline. put a predetermined mass of fuel in the car of a certain octane. Run about 40 tests and take the mean. IIRC 40 is the number where statistically each incremental test after that does not statistically significantly change the mean. Now change the octane and repeat all 40 tests.

Then and only then you can make assumptions if octane can change MPG.