Higher the Octane the Better?

[JOE]

Not to familiar with Octane ratings in the states, but in Canada, regular is 87, mid-grade is 89, premium is 91, and supreme is 94. (94 only available @ Chevron) I have never used regular, always mid-grade and up depending on how deep my pocket is. Just wondering though if anyone else experiences better performance running on the higher grades or not. I can fell the difference big time travelling over the mountain passes to Vancouver with the higher octane. What does everyone else use??

[brianp]

I use regular, and haven't noticed any problems. Though I could see that it might be good going over the passes.

[Typrus]

I use regular. King Soopers regular no less. I believe it is 84.. Maybe 85..
You can get 106 from a local store... Can't remember the name of it. My friend with a Supercharged 454 Suburban has to use it. It isn't cheap though....

I've run Super before, but I honestly saw no difference. Now, bear in mind 2 things. I live just over 5500 feet above sea level, and I have yet to attempt any of the 13,000 foot passes. I trek a 20 mile journey that takes me, depending on if I go to Fort or Love, anywhere from 300-800 feet variance in elevation. I also keep my engine fairly clean. Whenever I feel like it, I run a can of SeaFoam through it. Right now I'm doing a valve job and cleaning her out. Can you say smog machine?

I'm going to try some higher Oct now that the valves are adjusted to see what happens. After all, whats 10 cents more a gallon? lol.

[Ogedei]

Crazy that this post is here I was thinking about asking the same question. On my terc running better grade than regular results in bad performance. Terrible at start can not get it to idle up right. I start but I am missing a lot until I get warm and sometime can not keep it running. I do not like to warm up my engine with the pedal I would rather it warms up on its own time. With the higher grade gas I have to use my pedal.

With that said I can use regular gas and a octane booster and be fine. Not sure what exactly is the deal.

[MootsMan]

Something is screwed up with mine....for the last few months, I've had to run 92-93 octane to keep spark knock( or pinging ) from happening. With 87 octane, I get no performance at all. I hate paying the extra .20 per gallon, since I have to fill up every other day. Do y'all think this is a timing issue ? Most of you know what an ordeal it was for me to get the timing straightened out after installing my timing belt, but then the mileage was up around 31-32mpg. I'm down around 27-28 now, and that's mostly freeway driving, at around 65-70MPH. Keep in mind that my engine has issues....blowback into the air filter, although this isn't as bad now as it was a month or two ago. Seems like oil consumption has slowed after running a bottle of Bardahl through the system.

[Mac]

my tercel loves premium. reason being there are is carbon built up in the combustion chambers which causes pre-ignition, but also increases your compression ratio slightly. its common that a high milage engine will perform better with higher octane gas.

[xirdneh]

[quote="JOE"]Not to familiar with Octane ratings in the states, but in Canada, regular is 87, mid-grade is 89, premium is 91, and supreme is


here is something to consider. between the tercels and my full size ford truck i have found that i get 2-3 mpg more from 89 octane (plus) vs 87 octane (regular) on the tercels and 1-2 mpg more on the truck. all of my testing was done on long trips. when you calculate the extra cost of the higher octane and compare to the milage it all evens out. so i see no advantage to using regular from a monetary standpoint.
i suspect the same may be true for premium fuel but have never tried it.

[takza]

I think it's all a BALANCE between ignition timing...carbon buildup...and octane.

Where you could use regular and set your timing to where you don't have pinging above say 1700 RPM in 5th under 2/3s throttle.

Basically saying that if you would use 2-3 oz acetone per 10 gallons on a regular basis to keep the carbon down...you could then use regular and road adjust the timing to avoid most pinging.

Result? ......good power and reduced pinging.

Or...you could do the same thing without acetone...just less power.

I also run heated fuel which gives a 10% mileage gain in summer.

And I use NGK V-power plugs.

I run heated fuel and acetone have good power...no pinging.

[hberdan]

Octane ratings are adjusted for altitude; in Colorado, regular is 85 octane; extra is 87, and super is 89, generally. At lower elevations add two points, so regular at sea level is 87 octane. In theory, at least, 85 octane at 5000' burns the same as 87 at sea level...
The car was designed to run on 87 octane. It's in the manual.
I live in Colorado, and I run mine on 87; the engine knocks on 85; my other Tercels, the 84 and the 86, also run/ran best on 87.
It's worth the extra 10 cents a gallon to me when I can get good performance and good mileage too.
OTOH, if your car doesn't knock on lower octane gas, that's a good sign not to waste money on the more expensive grades; empirical knowledge is best.

[Soutthpaw]

Well if you understand what octane is you can select the best for your needs. the function of Octane rating is to prevent pre detonation of fuel in the cylinders which causes the engine to knock under load. Best to run the lowest octane rating possible without the knocking. generally you are just wasting money on higher octane gas if you dont need it.

Also in the US octane ratings vary by state.

[Typrus]

Its varied by air density, which typically means elevation. I saw 83 once up in a mountain town at around 12,000 feet.

Your best performance is usually attained with an octane just barely above the ping-point.

ALL that octane rating is is a rating as to how resistant a fuel is to auto-detonation (knock). That is ALL octane is. If your engine runs without knock throughout all the spectrum, and is not doing so based on a computerized adjustment of timing or mix, on 84, then you'll get nothing better on 87. If you get knocking somewhere, and new systems will eliminate it using timing and richness adjustments making you think it isn't knocking, then 87 will perform better. But 90 will do no better than 87, so long as the 87 doesn't knock.

Newer systems will fool you into thinking higher octanes are higher performance, because a lower-than-required octane fuel will result in a ping, which the engine senses before you can, and the car will stop the pinging. But in doing so, it will retard performance. The lower the octane, the more the adjustment, the worse your performance. But the higher the rating, the better, UNTIL it doesn't knock at all anymore, then any higher rating is pointless.