What octane should I run?

[JohnnyO]

unless your engine pings under load (predetonation) theres no reason to go for the expensive stuff.

Werd.
That said, later model vehicles have a knock sensor that will keep the timing advanced as far as possible, so if you were to run 89 you might see slightly better performance and mpg but probably not enough to offset the higher price of the gas. The timing will still remain within the window allowed by the computer.
That said, my dad used to have a car that required premium, at least 91 octane. When gas first got pricey a couple years ago he tried using 87 to save a few bucks. The knock sensor dialed the timing back such that he lost enough mpg that was actually cheaper to run premium. But again, that was a car that required premium gas to begin with.
That said, different parts of the country get different gas at different times of the year. When I had my '99 3.0 Ranger it hated the summer blend we get here and pinged like crazy. After many trips to the dealer I gave up and just ran 89 in it in the summers. Other parts of the country get the crappy gas in the winter.
So basically if it doesn't ping on 87, don't worry about it.

 

[shadetree]

Werd.
That said, later model vehicles have a knock sensor that will keep the timing advanced as far as possible,......

The knock sensor does not advance timing, only retards. If the knock sensor is not active, the timing is at it's normal setting.shady

 

[marc11]

I run 87 in my truck and in my motorcycle, that is what the mfg calls for. Occassionally I get light spark ping in the truck under heavy loads, like going up hills and towing and I may add 1/2 a tank of 89 which cures the problem.

 

[marc11]

I've always run 87 octane in the Ranger. Maybe once a year, I'll fill up with Shell V-power 91. On my Kawasaki KLX250s, I always fill up with 91 octane. Runs smoother with it at lower speeds.

Hey, I have a KLX250s as well (versys too and a KLX110 for my son) gotta love the KLX, great dual sport! But it'll run just fine on 87...Sorry for the off topic post...

 

[OilPatch197]

I use 93 in my truck when I can afford it. 93 has more btu's, and it is the only gas around that does not have ethanol(10%)

Any gasoline blended with ethanol (Gasohol) will have a good octane value but a really poor BTU value as Ethanol has such a poor BTU rating.

under $2 I use premium(shell V-power 93) if it's $3+ I use the cheap stuff.(summer)

In winter I use regular, because I have a choke.

I drive a '87 with a 2.0, gets better milage with premium, enough to justify the cost? probably not, but I am using less fuel.

 

[shadetree]

I use 93 in my truck when I can afford it. 93 has more btu's, and it is the only gas around that does not have ethanol(10%)

All gasoline grades for automobiles(with a few exceptions) have ethanol by federal mandate. There is a movement afoot to have it removed from premium, but not yet.

Premium has no more power than regular gasoline. The addition of power comes from the higher compresson ratio that requires the use of premium.

The only difference between premium and regular is the higher octane. The octane rating is the ability of the gasoline to prevent detonation in the engine. About the only way it will affect power is the higher octane burns slower, and can cause the engine to have slightly less power. Because of the slower burn, all the gas may not get burned, and can carbon up the combustion chamber and exhaust system leading to detonation and other problems.

Any gasoline blended with ethanol (Gasohol) will have a good octane value but a really poor BTU value as Ethanol has such a poor BTU rating.

True to some extent, but the amount is so small, unless you are using E85, that the effect is minimal. There is also a very slight decrease in mileage to the addition of ethanol, hardly detectable.

If I had a vehicle that used strictly E85, I would raise the compression ratio of the engine to take advantage of the higher octane.shady

 

[97ranger4x4]

So how to programmers work when you input the use of Higher octane fuel, say 91? To they adjust the timing to compensate therefore increasing power?

 

[OilPatch197]

Premium has no more power than regular gasoline. The addition of power comes from the higher compresson ratio that requires the use of premium.

Then can you explain how my 2.0L four banger gets 3 mpg better milage with premium from a perticular brand?

I can only assume it is in the additives.

I measured how much $ per mile for both Shell and Huck's to see which one is more beneficial regardless of the $/gallon ratio (which would persuade people to use Huck's due to the higher Shell prices), and found that you pay much less per mile on Shell compared to Huck's gas. For example, if you were to spend say $50 on Shell or $50 on Huck's, Shell will give you LESS gas, but MORE miles, therefore more beneficial because it's a less expense overall. While Huck's will give you much more gas for the SAME price, but it won't last nearly as long.

Huck's is advertised as "200%" gasoline BTW. :\

 

[Wicked_Sludge]

To they adjust the timing to compensate therefore increasing power?

correct. with a programmer you can change the timing and fuel curves to best take advantage of a higher octane fuel.

 

[shadetree]

Then can you explain how my 2.0L four banger gets 3 mpg better milage with premium from a perticular brand?

I can only assume it is in the additives.

Now don't go "assumin" on us there oil patch, you know how that works.

Only a few of the major refiners have dedicated pipelines where only their brand of gasoline goes to the dealers. The rest of the gasoline in pipelines is generic, and mostly the same. The different brands then mix different additives to the gas when it distributed to the dealers. So, all gasolines are not the same.

Also, you have winter and summer mixtures thanks to the EPA.

By the way patch, where do you live?shady

 

[rangerbum]

Only reason I run 93 is because there isn't any Ethanol in it. I dont support Ethanol, or like the way it makes my truck run a little rough. I have been using premium(93) lately because of how cheap it is, might as well!

........but, when my truck was stock, premium actually made it run funny, whereas now it makes my truck run great. When I ran it in my ranger stock It sort of sputtered a bit, oddly enough.

 

[Hawker]

Ethanol does deteriorate the performance of the fuel even while maintaining the burn rate (octane). While running 87 octane (w/o ethanol) produces a noticable difference improvement in (mpg/performance) vs. 87 w/ethanol. I don't see the same improvement going to 89 or 93 octane. You can't just compare one tankful vs another. This is speaking from my experience in my truck only.

I see the same improvement in mileage in my Miata using only 93 oct. w/o ethanol vs with.

My conclusion after watching this debate for years is that you use the octane fuel the car was designed for. There are no engineers who've done extensive testing lurking here on the internet that can begin to match what the manufacturer has done on this subject. If you want improved performance, find somewhere that has gas without ethanol.

 

[lil_Blue_Ford]

Not that I really want to open this can of worms but... I have to disagree to some extent.

I've driven an 89 F-350 with a bored-out 460 for work since around summer of 2001. Back then it ran great on 87. It ran so well on it that the joke at work was that the truck would run on water if you put it in the tank. More recently, however, it seems to lack power and not run nearly as good. Fuel economy remained the same, just a shade over 8mpg. Then the prices on gas started coming down an we ended up with enough money off a gallon of gas at the local place to put 89 in for pennies, so we did. Surprisingly enough the truck seemed to run a lil better and when we calculated the fuel economy, surprise, 9.4mpg. We've switched back and forth a couple tankfuls now and the results have remained the same, we get just a shade over 1 mpg better with 89. The tankful we're working on now is 93 octane, and I have to say it's running like a r@ped ape, just like it used to. Which makes me wonder what they're doing to our gas... I find it hard to believe that it could be the truck itself...

 

[Hawker]

Not that I really want to open this can of worms but... I have to disagree to some extent.

I've driven an 89 F-350 with a bored-out 460 for work since around summer of 2001. Back then it ran great on 87. It ran so well on it that the joke at work was that the truck would run on water if you put it in the tank. More recently, however, it seems to lack power and not run nearly as good. Fuel economy remained the same, just a shade over 8mpg. Then the prices on gas started coming down an we ended up with enough money off a gallon of gas at the local place to put 89 in for pennies, so we did. Surprisingly enough the truck seemed to run a lil better and when we calculated the fuel economy, surprise, 9.4mpg. We've switched back and forth a couple tankfuls now and the results have remained the same, we get just a shade over 1 mpg better with 89. The tankful we're working on now is 93 octane, and I have to say it's running like a r@ped ape, just like it used to. Which makes me wonder what they're doing to our gas... I find it hard to believe that it could be the truck itself...

I don't know that this is at all inconsistant with an engine as it ages. Carbon buildup can have the effect of raising the compression which would reduce performance. The higher octane adjusts the burn rate back to closer where it was when it was young. (you can explain this like giving an old guy a viagra - he adjusts to back like when he was younger. Give a young guy one and... I dunno,, could get bad) (that's all an attempt at humour - you can smile now)

 

[85_Ranger4x4]

All gasoline grades for automobiles(with a few exceptions) have ethanol by federal mandate. There is a movement afoot to have it removed from premium, but not yet.

I don't think it is federal yet.

Around here:

87 - regular, no mention of ethonal
89 - E10 or 10% ethonal
91-93 - premium, no mention of ethonal
E85 - 85% ethonal

I used to run 89 because it was cheaper and my Laser called for 90, but I traced my fuel line icing to it in my Ranger and switch across the board to 87, no more problems. Never had a problem with it in my Laser or F-150.

89 or E10 also gives my tractors fits, a little water condensation and the alcohol seperates out, engines with 6.5:1 compression new do not care for pure alcohol (which is heavier than gas and goes thru the carb first) Probably wouldn't be a huge issue if I farmed all the time with them, but if I fill the tank up it would go bad before I could use it all.

Not that I really want to open this can of worms but... I have to disagree to some extent.

I've driven an 89 F-350 with a bored-out 460 for work since around summer of 2001. Back then it ran great on 87. It ran so well on it that the joke at work was that the truck would run on water if you put it in the tank. More recently, however, it seems to lack power and not run nearly as good. Fuel economy remained the same, just a shade over 8mpg. Then the prices on gas started coming down an we ended up with enough money off a gallon of gas at the local place to put 89 in for pennies, so we did. Surprisingly enough the truck seemed to run a lil better and when we calculated the fuel economy, surprise, 9.4mpg. We've switched back and forth a couple tankfuls now and the results have remained the same, we get just a shade over 1 mpg better with 89. The tankful we're working on now is 93 octane, and I have to say it's running like a r@ped ape, just like it used to. Which makes me wonder what they're doing to our gas... I find it hard to believe that it could be the truck itself...

About the time the price started dropping they switched to winter fuel, which really dings milage as it doesn't have the energy of the regular stuff.