Octane Opinions

[Weldo]

What octane are you guys running in your trucks?  When you respond, make note of the engine (22r, 22re, etc.)  I've been putting 93 in my 91 22RE.  I figure it makes the engine run cleaner, and maybe a little better.  Higher octanes are supposed to protect against detenation, so I always figured getting 89 or 93 was like cheap insurance.  Opinions?

[FATB0Y]

I run 93 in mt 22re and 110 in my fatboy

[BLACKDOG]

87 in my 91 3.0   but I do buy chevron every once in a while 

[RokCrawlinToy]

My 3.0 runs fine on 87. only use Hi Octane in my cars. 

[BigMike]

I've been running 89oct 76 "ProPower" as first choice or 89 oct Chevron as my second choice. Nothing less

[guywithuglyyota]

Im no chemist, but I was always told to never run high octane in a car only requiring regular. I was told its because the timing on our trucks, and compression is designed for 87 octane. Anything higher will detonate pre-maturely, or burn hotter and cause pre-mature 02 sensor failure. Dont take this for gospel. I used to do the same thing in my accord and it never made a bit of differentce with how clean the engine was, my gas mileage actually dropped.

I do always run quality gas, Shell, 76 and if I have to Chevron, there is definate a difference in qaulity.


read the last paragraph if you just want to cut to the summary of this article.

http://www.csgnetwork.com/octaneratecalc.html

In internal combustion engines, the compressed gasoline-air mixtures have a tendency to ignite prematurely rather than burning smoothly. This creates engine knock, a characteristic rattling or pinging sound in one or more cylinders. The octane number of gasoline is a measure of its resistance to knock. The octane number is determined by comparing the characteristics of a gasoline to isooctane (2,2,4-trimethylpentane) and heptane. Isooctane is assigned an octane number of 100. It is a highly branched compound that burns smoothly, with little knock. On the other hand, heptane is given an octane rating of zero. It is an unbranched compound and knocks badly.

Straight-run gasoline has an octane number of about 70. In other words, straight-run gasoline has the same knocking properties as a mixture of 70% isooctane and 30% heptane. Cracking, isomerization, and other processes can be used to increase the octane rating of gasoline to about 90. Anti-knock agents may be added to further increase the octane rating. Tetraethyl lead, Pb(C2H5)4, was one such agent, which was added to gas at the rate of up to 2.4 grams per gallon of gasoline. The switch to unleaded gasoline has required the addition of more expensive compounds, such as aromatics and highly branched alkanes, to maintain high octane numbers.

Gasoline pumps typically post octane numbers as an average of two different values. Often you may see the octane rating quoted as (R+M)/2. One value is the research octane number (RON), which is determined with a test engine running at a low speed of 600 rpm. The other value is the motor octane number (MON), which is determined with a test engine running at a higher speed of 900 rpm. If, for example, a gasoline has an RON of 98 and a MON of 90, then the posted octane number would be the average of the two values or 94.

High octane gasoline does not outperform regular octane gasoline in preventing engine deposits from forming, in removing them, or in cleaning the engine. Consumers should select the lowest octane grade at which the car's engine runs without knocking. Occasional light knocking or pinging won't harm the engine, and doesn't indicate a need for higher octane. On the other hand, a heavy or persistent knock may result in engine damage.

[Uncle Jesse]

Octane ratings determine how fast the gasoline will burn.  That in turn effects timing.  If your timing is stock then run 87.  87 burns faster than 93.  If your timing is advanced, run higher octane.  Basically, if the fuel burns slower you need to start the spark earlier.  If the fuel burns faster, you can start the spark later.

[abnormaltoy]

Octane slows the burn rate of raw gas. It doesn't burn cleaner. It doesn't make a low engine compression engine "perform" better. What it does do is...allow you to run higher compression with out pre-ignition and it allows you to advance your timing with out pre-ignition. In fact by putting a (much) higher octane rated fuel in your truck you're actually decreasing it's performance. Because the higher octane gas burns slower, combustion isn't complete. If you're truck is "pinging" check the timing.
Mark

[lilbuddy]

91 Safeway Gas (actually is the same as Chevron gas. My friends dad is a trucker and puts the same Chevron gas as Safeway gas into the tanks) 22R, and timing is advanced. It runs like crap on 87. With 91, it runs grand.

[Weldo]

I was running 93 and it has not been pinging at all, runs great, even under hard acceleration.  I heard that an engine can run no problem on a low octane fuel, but under heavy load or high RPM, like under heavy acceleration, the lower octanes can cause pingnig and detonation.  Basically saying that your engine only needs the higher octane, maybe 10% of the time.  Next fill-up I'll get 87 and see if it knocks or anything under various engine loads and speeds.  If I notice any, maybe I'll move up to 89.  By the way, whats the factory recommended octane?  Anyone know?

[guywithuglyyota]

I believe it is 87. Japan uses something like 99 but thats there premium fuel.
Thats good to know about safeway gas. Im in the Air Force and we have a gas station on base with mystery gas in its tanks. People are constantly complianing about engine performance, poor mileage etc... I could not use it in my crotch rocket because it would not run right at all. A friend of mine had to have his brand new 750's fuel system purged after using it since it would not period. Some stations apparently have issues with water creeping into the tanks and fouling the gas.

The way gas prices are now 2.73 for regular here, im gonna stick with 87

[Weldo]

Are you sayin' that the factory recommended octane is 87 for American trucks and 99 for Japanese trucks?  If that is so, why the hugh difference in recommendations?

[whiteman]

83 in a 22re with 240,003 mi.  Although I will not use AM PM gas My girl friends jeep will not run off of it, her friend bought a new jetta and ran AM PM 83 octan and after 5500 miles her fuel injectors needed to be cleaned because it ran crapy.  I try to go with shell or 76.  110 in my Banshee! oh yeh! Smells like candy.

[abnormaltoy]

110 in my Banshee! oh yeh! Smells like candy.

Oooh, I love the smell of race gas!  and two strokes!

[BigMike]

Uncle Jesse and abnormaltoy have already said everything you need to know about this discussion.

When I was still in HS I did a comparison in my moms '87 4Runner by running two tanks on 87, then 89, then 93 oct ARCO (garbage gas). Back then gas was only $0.99/gallon/87oct but it still applies today because each grade is still ruffly 10 cents apart. What I found out by tracking my mileage was that I gained MPG by using a higher grade gas. 89oct got about 25 more miles per tank on average and 93 got about 30 more miles per tank on average. I was putting in around 14 gallons, so at these rates, it was like I was gaining about an extra 1.5 by using 89 oct grade gas and about 2 extra gallons by using 93oct.

Then I calculated the cost per tank. At 89 oct compared to 87, 10cents more per gallon would be $1.40 more per tank. At 93 oct compared to 87, 20cents more per gallon would be $2.80 more per tank.

So this means that by using 89 oct I was spending $1.40 more but I was able to travel the equivalent of about 1.5 more gallons, or $1.65 worth of gas (@ 1.10/gallon/89oct).
And by using 93 oct I was spending $2.80 more but I was able to travel the equivalent of about 2 more gallons, or $2.40 worth of gas (@ 1.20/gallon/93oct).

So what I found out with this 22RE engine is that by using 89 oct I was saving on average about $0.25 per tank of gas, and by using 93 oct I was actually loosing around $0.40 per tank of gas

Now sure I could have advanced the timing and done some other engine mods to make it more efficient at the higher octane range, but it was my moms (family) vehicle and I was still in HS. And Im sure many can agree that saving $0.25 cents per tank while getting more miles out of the tank was like finding gold for me in HS.
But if you think about it, I'm getting gas nearly 50-60 times a year - so if by paying more for 89 oct gas can actually save me $0.25 cents per tank and then cut the number of times I need to refill down to 40-50 times per year, now I'm saving myself some real dough. It's like having 10 free refills a year plus your using better gas!

Also, if you've got a newer vehicle, say 96+ with a better OBDII system, then it will automatically adjust the timing for you on the go. You run crappy gas, it will have to maintain a low timing. You run great gas, it will be able to run a high degree of advancement on the timing giving you more power and efficiency.

BigMike

Octane ratings determine how fast the gasoline will burn. That in turn effects timing. If your timing is stock then run 87. 87 burns faster than 93. If your timing is advanced, run higher octane. Basically, if the fuel burns slower you need to start the spark earlier. If the fuel burns faster, you can start the spark later.

Octane slows the burn rate of raw gas. It doesn't burn cleaner. It doesn't make a low engine compression engine "perform" better. What it does do is...allow you to run higher compression with out pre-ignition and it allows you to advance your timing with out pre-ignition. In fact by putting a (much) higher octane rated fuel in your truck you're actually decreasing it's performance. Because the higher octane gas burns slower, combustion isn't complete. If you're truck is "pinging" check the timing.
Mark

[FATB0Y]

Oooh, I love the smell of race gas! 

Me 2

[Weldo]

So in a 22RE, 89 may be the best bet.  How far would the timing have to be advanced to run 93 at peak efficiency?

[yotaboy79]

i had to run some 114 oct left over from my bike to get home once it actualy ran pritty darned good but i dont have any sensors or catalitic converters to fry

[yotaboy79]

and at damnd near 7 bucks a gallon its not realy cost effective

[Huhwhye]

What people like Uncle Jesse and guywithuglytoyota are saying is right.  You want to run the octane your vehicle was built to run on.  There is no benefit to using higer octane than specified especially on a stock vehicle.  The only thing you're doing is wasting money.  You aslo might be making your truck slower.  If the gas burns too slow and the timing isn't right all the gas wont burn efficiently.  Race cars use high octane because they are built to do so.  Now if you start modifying your truck like some people have done you might see some benefit.

Run the truck on both octanes at the track, on a Gtech meter, on a dyno, whatever.  With a stock 22r/re you wont see any difference.  Like I said only difference will be your wallet will be lighter.

I bought a flash programmer for my daily driver Ford Ranger.  It actually has a 87 octane program that makes a little more power/torque (2-3hp and 9lbs/ft of torqe) not bad for 87, I get better mileage to.  So that's what I use most of the time.  The dyno showed the horse power curve is substantially smoother too.  Small benefit but worth it.  I also have a high octane program dyno shows about 9hp and 16lbs of torque.  That's just for playing around, going to the mountains, or towing.  The High octane cost $2.70 a gallon around here.

[Huhwhye]

Also, if you've got a newer vehicle, say 96+ with a better OBDII system, then it will automatically adjust the timing for you on the go. You run crappy gas, it will have to maintain a low timing. You run great gas, it will be able to run a high degree of advancement on the timing giving you more power and efficiency.

BigMike

This is true to some extent but there is a limit.  If the car was built to run on 87 then the computer maps are made for that grade of fuel.  It is true if you get a crap tank of gas it will retard the timing to compensate, prevent detonation, damage to the engine.  But this is on a microsecond level here.  If the computer senses something wrong that second it will compensate but that doesn't necesarrily mean it will do it constantly.  And that is just if something is wrong.  But if you put 93+ octane in your car it will not advance the timing to take advantage of that fuel. As long as the sensors are not noticing something wrong, pinging detonation etc. things will remain the same.  And when you floor it the stock preprogramed maps take over completely and it takes no reading from the sensor.  And those maps have timing and fuel curves that are set for the grade of fuel the vehicle was built for.  There is always a margin of error too.  The engineers don't want to design a car to run on the higher end of the spectrum.  That way it will only run right if it always gets a good tank of gas.  They make it so when you get a bad tank of gas the car can still run o.k.  Margin of error/safety.

[Huhwhye]

Sorry I keep posting, but a didn't want to have 1 big post and I wanted to address ?'s separately.

Are you sayin' that the factory recommended octane is 87 for American trucks and 99 for Japanese trucks?  If that is so, why the hugh difference in recommendations?

Chances are the octane is rated differently in japan.  Next time your at a gas station read the sticker that says the octane on the pump.  It will usually show that octane is calculated by using a certain method.  There are 2 standards RON and something else (can't remember) then octane is calculated by the weighted average of the 2.

So in Japan they might have their own standard.

[Weldo]

I bought a flash programmer for my daily driver Ford Ranger. It actually has a 87 octane program that makes a little more power/torque (2-3hp and 9lbs/ft of torqe) not bad for 87, I get better mileage to. So that's what I use most of the time. The dyno showed the horse power curve is substantially smoother too. Small benefit but worth it. I also have a high octane program dyno shows about 9hp and 16lbs of torque. That's just for playing around, going to the mountains, or towing. The High octane cost $2.70 a gallon around here.

So when you say you made more power with a higher octane program, I assume you advanced your timing and made other necessary changes to take full advantage of the higher octane fuel?

Also, if I advanced the timing on my otherwise stock 22RE a few degrees, could I possibly get better performance and mileage by running 93?

[kyle_22r]

i've thought about straining out our bucket of waste gas(from customers lawnmowers that have been sitting for years, probably mixed witih a little hy-tran since that's what the bucket originally had) at work and burning it in my truck.  probably would give me some hellish carbon deposits and clog my fuel filter before i burn it all off from all the varnish in it, and it'd probably gum up my spark plugs, but i think otherwise my truck would love it.  i've always ran the cheapest gas i can find in my toyotas, 22Rs love the stuff!

[Huhwhye]

It's more than just adding timing, they adjust the advance curve.  They also adjust the fuel delivery to optimize performace.  They take a bunch of similar vehicles with different levels of modification and they test them so they see how they respond and where the factory put them.  Then they can come up with programs to improve power and torque.  It seems to work pretty well.  The dyno I saw was from a person on a different forum, a reverend no less so he can't be lying right    What is also interesting is these guys came up with a program that does something with 87 octane.  Most places will tell you they can't do that and there's no benefit to a 87 octane program.  That's because they don't do their own programs.  They buy programs from people who make them and sell to chip companies.  Hypertech for example doesn't impress me.  They won't do an 87 program, last I checked all they have is a 93 octane program.  Here in Cali the best gas we have is 91.  I asked them about it and they said it won't work and they have no interest in making (or buying) something for the California market.  Jet won't do an 87 octane program and they also won't remove my speed or rev limiters.  Technically I'm buying a Superchips tuner but with programs made by a third party.

The guy doing my program is a Ford Master Tech and started his own business on the side.  These programs were in part developed by him and in part developed by a Ford chip guru that used to be independant and now works for superchips.  It also comes with a cable that plugs into my laptop or P.C. and allows me to fugde with things myself including Axle Ratios and Tire sizes, Idle / Part Throttle / Full Throttle Air / Fuel Ratio, Engine timing and idle, Automatic transmision shift points and pressures, and finally Rev and speed limiters plus this guy and email me updated programs or modify the programs if I add modifications to the truck.  Then I download the program into the tuner and put it in the truck free of charge.

[Uncle Jesse]

I guess what it comes down to is does your truck run good on 87 octane?  If it does, stick with it.  Little mods like a few degrees of timing and higher octane are not going to make enough difference in performance to warrant doing them in the first place.  As far as I know ecu's have no way of telling what octane fuel you are running in your car.  Some older vehicles had a jumper you could short to adjust for octane, but that has gone away.  Also, remember that we are talking about adjusting static ignition timing.  Fuel injected vehicles have ignition advance adjusted on the fly as you drive down the road, and you have no control over it.  As you go down the road normally, spark advance increases because the burn rate of the fuel stays the same, no matter what rpm you are at.  The faster the engine turns the earlier spark happens because the fuel still takes the same amount of time to burn.  So now add some high octane slower burning fuel.  And you've only changed static ignition timing.  So overall timing will be advanced, but the engine control still may not compensate fully for it.  Blah Blah Blah, we could go on forever, but my owners manual doesn't tell me to run premium, so I'll stick with 87.

[Weldo]

Sounds like I'll be filling up with 87 from now on!  So here's my next question, is there a point when you've modified your trucks motor that it becomes a good idea to run a higher octane.  What I mean is, say I took a stock 22RE and added a header and 2 1/4" exhaust, a cam, and a high flow intake...would I want to go up to higher octane?  How about if I added some low compression pistons and a turbo?

[abnormaltoy]

Well...a low compression engine becomes a high compression engine when you throw a turbo on. I run 91 octane in mine because I've got 11:1 compression. Right now the engine is out (hell the whole truck is out!), but I've got an SDS ignition/fuel system, header, LCE head and a (gasket matched) late intake that will have a 5.0 Mustang throttle body on it. I basically set the timing by trial and error...advance it until it starts pinging then back off a wee bit.
Mark

[yotaboy79]

usualy as compretion increases so does the need for octane for instants my motorcycle because of all the work ive done to it im stuck running straight 114 oct race gas in it other wise it will start detonating because of all of the compretion

[abnormaltoy]

Remember, compression is free HP...up to a point!