Discgolfer74

So, I filled up with 100 Octane a couple of days ago, but don't notice a difference (except my wallet is a bit lighter). Since the gas prices have gone down, I have been consistantly using 94 Octane vs 91/92. I thought I'd give the 100 a shot at $6.749 per gallon, but feel like I just threw my money away. What was I to expect from the high octane?

Supafly

using 100 octane will not do anything unless you have re-tuned your map.
it will be just spit out your tailpipe as you're not fully burning all the fuels.

Up here in Canada i pump 94, the reason behind that is because it has its own pump....All the 87-92 share the same pump...Chevron ftmfw.

cayman63

dumbass

trikoid

Most modern cars are tuned for a specific octane, in our case 92 (if I'm correct). With knock sensors, the computer can retard the timing if running lower octane, but I don't think it will advance the timings beyond that useful for 92.

Also, the biggest use of 100 octane is for those running turbos or really high compression ratios so that they can tune them with high boost AND advanced timings without knock.

Discgolfer74

Lesson learned...

but the acceleration did feel smoother when I opened it up yesterday. Maybe it was all in my head. Kinda like how it feel like it runs better after a fresh wash

So, when I upgrade the chip, the higher octane would make a difference? Or should I just stick to the 94 Octane?

tom0329

Octane is the speed that the flame wall advances across the combustion chamber. The high the octane the slower the burn. If you go to high with the octane chances are you are pouring unburned fuel into the exhaust system. That could heat up the cats and damage them.

trikoid

Tom has a point.

However, if you get chip for your car, it will likely advance the timings. You can probably ask about that, and in fact I think I've seen chips available with tunings for different octanes. Tell them what octane you will be using every single day, and they can set the timings to match that.

But in the end, you should use the gas your car is designed for. Big example: my dad tried 94 octance in his 1987 Corvette, and it ran horribly. the mechanic told him to use 87. High octane isn't "better" it's "different." A slower burning gas (94, or 100 in your case) is useful sometimes, but it can be a detriment other times.

I would believe you if you think the 100 octane was smoother feeling because of the slower burning. Did it seem faster too? I'd be a little surprised unless you had a turbo...

Discgolfer74

I don't want to say it was faster. The acceleration was so smooth, I didn't notice that I was already over 100MPH. I typically drive 80MPH - 100MPH on my way to and from work, so I can't really say. It doesn't seem to need much throttle to get up and go though. Unfortunately, I haven't noticed any improvement in my MPG.

Okay, I found where I got this fantastic idea: thread link

I was really hoping for a nice HP gain.

seephor

The main purpose of higher octane is for engines that run high compression which increases the likelyhood of knocking (premature combustion induced by heat/compression). The higher octane fuel takes more to combust as well as burns slower. if you use higher ocane in an engine that is designed for a lower octane, you'd basically be expelling unburt fuel which may damange emission componenets etc.

Uninformed people quite frequently associate a higher value product to mean something better which is the case most of the time but doesn't apply to the octane rating. The higher cost of high octane fuel is mainly due to the lower demand for it.