Lower MPG om high octane fuel?

[127.0.0.1]

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.

[woof]

I've never owned a four-cylinder that actually like 87 octane (USA's lowest). I always end up using 91/93 and always get better power and mileage everytime.

When you drive a manual, you seem to really feel the smaller differences sense you are more attuned to the car's pulse.

[127.0.0.1]

Originally Posted by woof

I've never owned a four-cylinder that actually like 87 octane (USA's lowest). I always end up using 91/93 and always get better power and mileage everytime.

When you drive a manual, you seem to really feel the smaller differences sense you are more attuned to the car's pulse.

I would love to dyno this comment...if you are talking about a motor that will
ordinarily use low octane.

in a motor designed for 87 and above, (the Toyota VVT-i Yaris motor)
and if it is has no maintenance problems, what you state is not possible
except with bad gas...which can be a real issue depending on where
you get your gas and the tanks they store the bulk in

you simply cannot go faster and get better mpg with a hydrocarbon
that has less energy content -unless - you boost compression and air

[tcpty]

Originally Posted by 127.0.0.1

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.

RIGHT ON THE MONEY!! EXCELLENT EXPLANATION !! KUDOS!!

[Yaris Hilton]

Originally Posted by 127.0.0.1

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.

All of that's true except the first and last sentences. Higher octane fuel doesn't inherently have less energy per gram, and running higher octane than necessary won't hurt your mileage or performance. You just won't gain anything, and will have wasted your money. Now, if the higher octane is gained by adding more alcohol or other "oxygenates," then the first and last sentences become true. But it's because of the lower energy density of "oxygenates," not because it's higher octane. That is a common way for different octane levels to be produced today.