But how did this translate into performance and other things like fuel mileage, plug life, etc?

 

What about 90 octane, where I live they offer 87 - 90 - 91, the 90 octane is 10 cents cheaper and with a discount card they will knock off another 10 cents in my college town, I thought about calling the dealer and asking if 90 octane is okay to use. I am just wondering if there is much of a difference in performence, anyone ever called to ask?

 

Honda calls for 91 octane. However, if you use lower octane, the ECU just pulls a bit of timing to compensate. No harm done, not a big deal, but you will lose a little power. In the other direction, going to a slightly higher octane "may" help the engine make a little more power, but above a certain point, high octane does nothing - no power gains, no harm unless the octane was achieved using lead or high concentrations of alcohol.

 

I have a station down the street from my house that has 100 Race Gas at the pump. But t $6.00 a gallon it is not worth it.

 

"Race" gas does nothing for an engine that's not tuned to use it.

 

Thanks for the feed back guys.

 

Correct me if I'm wrong, but using lower octane gas isn't even noticable until you try to accel hard, and there's just less power, right? Its my understanding that since 'normal' driving doesn't require much hp to begin with, the extra octane isn't fully utilized until you push the limit - there's less power, but you don't really notice until you're mashing the gas.

 

The knock sensor is tuned to 91 octane fuel. That's full timing advance. As the ECU detects knock it dynamically rolls back the timing causing spark later in the cumbustion cycle and reducing horsepower. If you use 89 octane fuel you will never notice it, you will just kill power by some X%. If you use fuel higher than 91 you may get more power but not if the ECU doesn't detect knock using 91 because it's already on maximum advance and doesn't advance further than that. It all really depends on knock and not on fuel grade.

110+ octane fuel is made that way by adding lead as an octane booster. Lead will destroy your cat, O2 sensors and just about every other polution control device. It's very bad stuff we got rid of 30 years ago. 105 is about as high as you can get without going to lead as an additive.

100 or 105 race fuel is made for cars with extreme timing advance, high compression and or boost. Your factory ECU will never know it's running $6/gallon race fuel and neither will you. Your car will simply see no knock and leave the timing advance on full just as it would if you used $3/gallon 91 octane pump gas. You are doubling your gas price with no benefit whatsoever.

The only way to take advantage of the higher octane fuel is to advance your timing further than what the factory ECU will do, this will give more power to a point and requires a tuner ECU like AEM or Motec. It also requires a tuner to dyno the car and ajust it to the fuel you are using. If you tune it to 95, using 100 is pointless. There is only so far you can go until you start increasing compression which increases the likelyhood of detonation and you'll need to shift to a higher grade still. Add more compression in the form of boost and you go again.

A stock motor and ECU can't make any value out of gas which doesn't detonate at the ECU's most agressive timing settings which is 91 octane pump gas. Lower than 87 may cause engine damage.

Octane is a hydrocarbon which burns, it doesn't explode. Heptane the "other" gas is volatile and detonates. Mixing these two gives you gasoline and mixing them at a ratio allows you to control how evenly and violently it ignites. Auto manufacturers have settled on 87 and 91 octane as the two ratios they build their engines to use and what the oil companies produce and pump to gas stations.

You can't change that unless you go "off the grid" and buy specially formulated gasolines from specialists. They produce 95, 100 and 105 flavors and also some above that with lead additive. Lead increases the "effective" octane rating (does the same thing as octane in the mix). Octane is more expensive to produce than Heptane so it costs more at the pump.

Jet fuel is for a different animal, a jet engine. In a jet engine air is compressed, fuel is added and ignited. The burning of fuel in the presence of compressed air causes an intese continuous burn and release of energy. Jet engines are ignited like a torch and stay lit the whole time being fed a steady stream of compressed air and fuel.

liquid rocket engines are similar to jets but their pure O2 or NO2 is super compressed and pure. The combustion is intense fed by compressed oxygen but that catalyst is in limited supply so rockets can only burn for as long as their oxidizer lasts. The beauty of havig so much oxigen is that you could use any carbon based fuel. I've seen rockets powered by salamis and recycled rubber tires (spaceship 1 got to space on O2 and good years.

That's not how a piston engine works and the fuel requirements are therefore different. Explosive fuel in a jet engine is bad, that's not what you want. In a car it's needed but only to a point. That volatility needs to be controlled, burn but with a bang igniting the entire chamber at once and having it burn completely and evenly. That's what gasoline is for. Octane tames the ignition of the Heptane so you don't blow your engine to bits.

 

 

True the Honduh doesn't notice better fuel. According to my Senior Logging Technician the 96 octanes lowered timing by a few degrees vs. 91. This is very bad. Why? Less timing leads to