Lower MPG om high octane fuel? - Toyota Yaris Forums

127.0.0.1 · 10-06-2009, 01:06 PM

higher octane means less energy per gram of fuel

it only makes more power if:

you have higher compression engine that can make use of the
(obviously) bigger injectors, higher air/fuel compression pre-spark and pack
more air in (bigger intake, forced air induction)

or

if you have a normal motor, but it is running crappy or has deposits
on the cylinder, or for whatever reason the knock sensor is always
retarding the ignition...then high octane might make the knock sensor
quiet down and you'd get better overall performance. But this
is treating a symptom not fixing the root cause

High octane fuel in an engine that doesn't need it is a waste of money
and you get less mpg

all high octane does is, it has less tendency to detonate at the higher compressions,
[so you can squeeze the crap out of it and then light it]. Now you get more power and
speed, and perhaps the same MPG. but without high comp pistons, and special
intake mods (turbo-blower) and an ecu designed for it...you will only end up with less
power and less mpg with high octane.

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10-06-2009, 01:06 PM	#2
127.0.0.1 Banned Drives: '10 Yaris5drHB+99 4runner LTD Join Date: Sep 2009 Location: NE Posts: 672	higher octane means less energy per gram of fuel it only makes more power if: you have higher compression engine that can make use of the (obviously) bigger injectors, higher air/fuel compression pre-spark and pack more air in (bigger intake, forced air induction) or if you have a normal motor, but it is running crappy or has deposits on the cylinder, or for whatever reason the knock sensor is always retarding the ignition...then high octane might make the knock sensor quiet down and you'd get better overall performance. But this is treating a symptom not fixing the root cause High octane fuel in an engine that doesn't need it is a waste of money and you get less mpg all high octane does is, it has less tendency to detonate at the higher compressions, [so you can squeeze the crap out of it and then light it]. Now you get more power and speed, and perhaps the same MPG. but without high comp pistons, and special intake mods (turbo-blower) and an ecu designed for it...you will only end up with less power and less mpg with high octane.