rdharper

I suspect this would break differently for 22re's and 3VZE, but thought I'd keep it simple to start with...

Elton

ive owned a 22re the 3.0L and now the 3.4L and ive only used 87 and i have had zero problems

95RunnerSR5

87, there's another thread about this. unless you have pinging issues, forced induction, or a suped up engine, 87 octane is better than any of the others

AH64ID

An engine that has older technology, prior to OBDII, will get some minor performance gains from increasing octane. OBDII computers, most anyways, are designed to run on 87 and 87 alone. Increaseing octane only increases your fuel bill, unless you reprogram for it..

Now the 4.0L is more advanced enough it notices the difference and compensates for it. In fact the owners manual even says for increased perfomance use 91 octane. But ours runs fine on 87, or 85.

LOCKnGO

When I first moved from Connecticut to florida I had a bad Pinging problem,I was feeding her 87 up north down here i had to switch to 93.... that was untill I discovered a cracked dizzy cap. 87 all the way now.

BigWavePaul

iTrader: (1)

My choice of fuel is 87 octane. I choose to put in the good stuff because that's what the owners manual calls for. Being in Colorado Springs, we have a choice of 85 grade up here, elevation: 6500 feet. An 85 octane fuel burns the same as 87 octane would at sea level. The reason that the 85 is like 87 up here is the air/fuel mixture. I checked my owners manual and it says that 91 is best for this beast-94 Toyota, DLX, 4X4. I want the good stuff, she deserves it. So, I put in 87 up here to burn like the 91 would at sea level. When we roll home to Alabama it will be 91 until I get sick of the price difference. The only thing that octane is for is to eliminate knocks and pings. Race cars have high compression ratios, about 9.5:1 or more and the pinging on 85 or 87 would literally rattle them to death. I'll bet that my truck would run on beer as long as the percentage was above 5 or so! It keeps me goin' strong.

WashingtonApple

89 for me, at around sea level. My 22RE has 242k on it, does seem to ping pretty bad on 87, and less on 89, plus I need all the help I can get to coax it up some hills. I dont know how much difference it really makes with the power but theres something to be said about the placebo effect.

crackerjack

Boy this is one of "those" threads...I guess what I've gathered so far is
1. Higher "Octane" has nothing to do with oxygen moliculs which would make gas more explosive (lower octane is more explosive)
2. Higher Octane is less efficient and slower to explode
3. this is where it gets fuzzy for me,...so because its less explosive the timing has to be advanced more, spark ahead of TDC
4. high octane because it is slower to explode a higher compression can be built into engine with higher compression you get a bigger explosion hence more power???

ken.vs.ryu

i can't wait for $0.99 87!!!

bodo

Is this the same thread as "Fuel"? Seems like a waste of space to have the same thread on the same page.

rdharper

The key is to think about when it would be ideal for the force of expanding gases to be applied to piston.

All this playing with octane, timing, compression ratio, is to get as close to that ideal as possible.

If you have a high enough compression ratio, you don't need a spark.. as in a diesel. But if you use gas, instead of low volatility fuel such as diesel, you'd explode the gas way before the start of the power stroke.

On the other extreme, suppose you use diesel in a gas engine.. you'd have a hard time getting it to burn and expand at all at any point in the power stroke.

85 Ethanol is a relatively low volatility fuel, not as low as diesel, but way less volatile than gas. Burning that can be accomplished in a standard gas engine by playing with timing and compression. And rot proofing all the fuel lines etc.

ovrrdrive

Higher octane has a higher resistance to detonation. That's it.

The rest of that is myth and bunk.

The only one that deserves a comment is #3. Higher octane does not require more advanced timing, it allows bigger advances. You retarded or factory timed vehicle will run just fine on 100 octane, albeit with no benefit at all.

ovrrdrive

http://www.pontiacstreetperformance....Mythsgas1.html
http://auto.howstuffworks.com/question90.htm
http://www.state.mn.us/mn/externalDo...ctaneFacts.pdf

snap-on

87 most of the time 89 or above when towing because ill start to get pinging when the motor runs hot under load.

CoedNaked

Gas is usually comprised of Octane and Septane. Octane resists burning while under compression well. Septane does not resist compression well and if it is compressed it burns/explodes readily. Septane is cheaper to use than Octane, hence this is why less Octane gas is cheaper. So if you have 87 Octane, you have less Octane than 93 Octane as an example, but more Septane than 93 gas.

Now bearing that in mind, the more you compress the fuel/air mixutre, the more powerful of an explosion it has, driving the piston back harder. But the key is to compress the gas, and have the sparkpug ignite it, you don't want to compress the gas and have it explode from the compression prematurely igniting it alone. Remember that the piston is timed with the spark plug. If you compress it and ignite it without the spark pug this can bend a rod because the Piston hasn't reached the top of it's stroke (when it has compressed the gas the most for the most powerful explosion). If your truck doesn't have a high compression ratio to begin with, then you won't need the higher octane gas as long as you don't expierience pinging because it compresses the gas and it resists detonation/premature burning and it explodes fine.

Having said all of the above, I run 89 Octane just to be safe. My truck rarely pings, I've heard it here and there while pushing it up hills and such, so I like the insurance that 89 provides.

Homer666

If I'm not towing my trailer - I will stick with 92 octane from the local Husky. If I'm towing my trailer, then I will track down some of the "Truckstop Husky's" that carry 94.

I also carry octane boost with me at all times - I don't trust the gas stations we run into out in the boonies (I ended up having to toss in 2 bottles of Octane Boost just to tone down the pinging caused by 1 tankful of so-called premium gas from a backwoods station).....

crackerjack

THX I was kinda grimmasing waiting for the "hay dumby" replies to come haha
The diesel comparison helped to clarify THX

Keggo

I only use 91... it's only at most a dollar or two more per FULL fillup...

AH64ID

Where I live husky sells the cheap oxygenated gas, where 89 really acts like 85-87, 91 like 87-89 and they dont even have 94... but crappy gas it is...

Where are you at? Glad to hear Husky isnt the bottom of the barrel gas everywhere...

ovrrdrive

You know, in other situations people pay premiums for oxygenated gas.

More oxygen in the fuel leans out the mixtures which allows people to use bigger jets, or fuel curves as it may be, and produce more power without having to rely on advance and compression alone.

VP oxygenates a lot of their fuels and people pay big bucks for that...

http://www.vpracingfuels.com/vp_01_fuels.html

Are you sure oxygenated fuel is a bad thing?