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Old 03-09-2008, 07:14 AM   #1
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Octane rating

Does a 2002 4Runner require 91 octane, or is 87 fine. I looked at the owners manual but it says that 87 is required with some other rating of 91. So I couldn't determine which it's supposed to use.
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Old 03-09-2008, 07:18 AM   #2
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Yes, 87 is fine.
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Old 03-09-2008, 07:55 AM   #3
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I use 85, which is considered regular up here (due to elevation). Whatever octane "regular" is, that is what you need to put in.
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Old 03-09-2008, 08:52 AM   #4
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sweet, thanks
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Old 03-09-2008, 09:17 AM   #5
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Does a 2002 4Runner require 91 octane, or is 87 fine. I looked at the owners manual but it says that 87 is required with some other rating of 91. So I couldn't determine which it's supposed to use.
87.

This is an endless debate it seems. Truth is, all modern engines must run correctly on '87.

As to how well, my Ridge manual states 87. Further, they state you are wasting your money to use a higher octane. This is correct, and the frist manual I've ever owned that puts this fact in print.

Some like to believe they are "taking care of their baby" or some such comment.

Some have a problem with their EC setup, which seems to helped by higher octane.

Some mod their vehicles such that they think they must run higher octane.

Because of EC designs, the timing adjusts to correct for pre-ignition. There is actually more energy in lower octane fuel. If your vehicle works correctly, you lose no power, and have a lower cost per mile.

Period.
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Old 03-09-2008, 09:30 AM   #6
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Some vehicles must use high octane, I just wanted to make sure the 4Runner was not one of them. My Camaro needs high octane, 10.5 to 1 compression, runs horible on 87, it contiues to run/knock after you shut it off. The supercharged Frontier I just sold needed it, if I used 87 in it, it would retard the timing and dump the boost, resulting in no power and very bad mileage. I understand that every vehicle will "run" on 87 but if it's not designed to it will lose power and the mileage will suffer.
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Old 03-09-2008, 11:11 PM   #7
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I use 85, which is considered regular up here (due to elevation). Whatever octane "regular" is, that is what you need to put in.
Is that any cheaper than 87 in other places?
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Old 03-12-2008, 11:03 AM   #8
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Because of EC designs, the timing adjusts to correct for pre-ignition. There is actually more energy in lower octane fuel. If your vehicle works correctly, you lose no power, and have a lower cost per mile.

Period.
Octane has nothing to do with the energy in gasoline. It controls the rate of burn for the fuel. Higher octane burns slower than low octane, this gives longer expansion during combustion.
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Old 03-12-2008, 11:28 AM   #9
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Is that any cheaper than 87 in other places?
Seems like it. I was out in Reno a couple of days ago, and 87 was up around $3.30 or something like that. Here in UT, it's $2.90 for 85. The difference in Octane and location probably has a lot to do with the price difference.
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Old 03-12-2008, 12:20 PM   #10
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Octane has nothing to do with the energy in gasoline. It controls the rate of burn for the fuel. Higher octane burns slower than low octane, this gives longer expansion during combustion.
octane doesn't have anything to do with the energy content...correct in a literal sense

BUT

in gasoline for automobiles, higher octane gas has less energy per liquid unit than lower octane gas

if your engine can run on 87, use it for better mileage

if you have higher compression engine which requires a higher octane to prevent detonation, use the higher octane stuff


the only benefit of higher octane on a taco or 4runner, is if you have done
engine modifications and are using high compression pistons, new ecu program, and radical cams, then you will get some performance out of higher octane gas. the fact you are running higher compression cancels out the energy loss of the higher octane fuel, so you end up faster from the engine mods and the fact it doesn't detonate


using high octane gas in an engine that doesn't require it, just lowers your mpg and empties your wallet

--->usually, but not always. in special high octane formulations that you cannot buy at the local gas 'n sip,
you may find high octane -and- high energy fuel. this is specially formulated and not available in stores.
--------------------
read up

http://en.wikipedia.org/wiki/Octane_rating

Last edited by edzo; 03-12-2008 at 12:28 PM.
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Old 03-12-2008, 12:26 PM   #11
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does having variable Valve Timing, and ignition timing give you any more power while running premium, than just a regular fuel injected engine?

BTW, both engines normally run on regular.
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Old 03-12-2008, 12:37 PM   #12
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Octane has nothing to do with the energy in gasoline. It controls the rate of burn for the fuel. Higher octane burns slower than low octane, this gives longer expansion during combustion.
The point is, octane modifiers occupy volume. Which translates to less energy per unit volume. 87 octane has more energy per unit volume than 93, for that reason.

Of course it doesn't do you any good if you can't tap that energy. Pure gas would have the lowest octane, and the highest energy per unit volume.

Capiche?
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Old 03-12-2008, 12:52 PM   #13
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does having variable Valve Timing, and ignition timing give you any more power while running premium, than just a regular fuel injected engine?

BTW, both engines normally run on regular.

nope, no more power

it will if you have higher compression to go along with the fancy timing, but it isn't the gas giving the power, it is the fancy mods. the octane allows you to tweak the mods and compression without 'sploding to bits
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Old 03-12-2008, 12:58 PM   #14
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I have a 91 4Runner and it seems to prefer high octane fuel
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Old 03-12-2008, 01:04 PM   #15
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Higher octane gas CAN give you more power. If the explosion occurs too far before TDC, part of the energy from the explosion pushes the piston BACKWARDS. Most of the energy will still be exerted on the downstroke, so the engine will continue to turn over properly and produce some power, but not as much. High octane gas insures that it is the spark that ignites the fuel and not the compression.

As a result, your engine my "ping" under heavy throttle. If you were to test out a multitude of octane ratings, you would find that say, an 83 would give very little power, the 85 modest amount, 87 full power and no benefit from going to a 89 or 91 octane.
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Old 03-12-2008, 01:12 PM   #16
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does having variable Valve Timing, and ignition timing give you any more power while running premium, than just a regular fuel injected engine?

BTW, both engines normally run on regular.
VVT and ignition timing allows your engine to run correctly over a broader range of fuel and rpm's. In fact it allows the use of lower octane gas with the same compression ratio, all other things being equal. VVT also can give you more torque at lower rpm's
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Old 03-12-2008, 01:28 PM   #17
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VVT allows most IC engines, depending on how it is applied, to run more efficiently (more mpg's) and produce slightly more power at a given RPM.
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