What octane gas do you guys run

[j.o.y.ride]

So yours sounded smoother with the higher octane? I have used 93 last to fill ups and I feel my jeep runs smoother

Yes it definitely was smoother with 91 added to the 87.

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[Trippin01]

87. JT is very happy with it to

 

[jbmdux]

I've only used 93 since i bought it. There's a Chevron by work that has the best prices in town. 93 is the same price as 87 elsewhere. I was getting about 22+ MPG. A few days before the pipeline deal the prices at the gas station increased, so I just used 87. I got less milage, 17+mpg but i feel the performance is the same. The owner's manual specifically says that higher octane won't net better performance, while that may be true. The MPG most defiantly increased with 93.

Where is 93 the same price as 87? Around Marxsachusetts 93 is always 40 cents per gallon more.

 

[jbmdux]

There is a lot of misinformation about "premium" fuel. It is not premium, it simply has additives that prevent it from detonating due to compression (like diesel engines). The fuel companies/ suppliers are making a ton of money off the terminology and gullible people, they could probably sell it for a pennies per gallon more and more than break even. If your fuel/ignition management system can run the lower octane (octane is another stupid term) you are okay but will have slightly less power and possible lower mileage but for the 20% premium you pay for "premium" fuel you are probably financial better off with the 87.
Yes there are some engines that require the additive to prevent the explosion before the top of the compression stroke. I am not sure what that compression ratio would be or how much turbo or supercharger boost would affect it (it would but I have no idea how much).
I had an Acura MDX and in the owners manual it said 91 recommended but 87 was acceptable but they provided a HP rating 5 HP less. I run 87 in my BMW 320 iX with the 4 cylinder turbo and have as much power as I ever need and I get 28 mpg highway with cruise at 75.

 

[ShadowsPapa]

Octane is actually a perfect term - octane refers to the ability of a fuel to resist self-ignition.
There is no explosion - that's a misnomer.
Detonation is also "usually" after TDC (ATDC), not before. It takes time to build up the pressure and heat.

PREIGNITION is before because it's a ping or knock caused by something igniting the charge BEFORE the spark occurs (trying to correct the use of "pre-detonation" because there is no such thing, there is PREignition, OR, detonation)
Preignition is a ping or knock caused by the charge being ignited before the spark by something hot, like the edge of a valve that's gotten way hot (and usually from a crappy valve job) or by CARBON or anything else that glows in the chamber and ignites the fuel before the spark, causing way early ignition and burning.

Detonation is when the normally burning charge's flame front forces the remaining unburned charge gases "into a corner" so to speak, compressing it to the point of self-ignition. This takes time, it's a burn, not an explosion. When the unburned gases get compressed to the point of self ignition, a second fame front forms and heads toward the normal flame front and the two collide - sonic boom and it resonates in the cylinder walls "PING!" The higher compression the engine has already, the more easily the unburned fuel can reach that critical stage of heat from compression causing self-ignition. The unburned charge is STILL COMPRESSED in a lower compression engine, but because it's started out at higher pressures in an engine running higher dynamic compression, it's going to reach a higher end pressure and reach is faster in a higher compression engine.
Keeping the heat removed, and keeping the charge MOVING, "swirl" keeps it mixed up so you don't have two flame fronts marching toward each other like Roman soldiers in a line. This is why intake design is important, chamber shape and design is important, and other factors - once the charge is in there, keep it moving around, keep it stirred up, then you can't have two lines or flame fronts. It's literally like stirring a trash fire or leaving it be and watch it burn in a straight line across the trash.

This was part of our engine course in college and I studied it as part of my Sun Systems fuel system training years ago, and I've done research over the years to find out the causes, how to prevent it, and how to build engines less prone to either or both preignition and detonation.

Preignition - the charge is ignited before TDC by something hot and/or glowing in the chamber, often a bit of carbon, but can be other causes.
Detonation happens when a second flame front forms "normally" after TDC (ATDC) - it's caused by the remaining unburned gases being compressed to the point of self-ignition by the normally burning and progressing flame front. Depending on RPM, speed of the normal burn, when the charge was ignited by the spark, etc.........pressures are normally highest after TDC.
In all cases, there is no explosion, it's a controlled burn. The charge burning in the combustion chamber takes time - that's why you ignite it - start the burn before top dead center (BTDC) by a few degrees (often as much as 30 degrees or so) and the peak combustion pressures happen AFTER top dead center (ATDC) at about 14-16 ATDC. In other words, on an engine running rates RPM max power the charge may be lit at 34 degrees BTDC and the peak burn pressures happen at 14 degrees ATDC - that's 48 degrees of crankshaft rotation to even achieve peak pressures - and it's still burning, controlled hopefully, no explosion.
I have written papers on the burn process, and so on, but it's a long read with a ton of detail on the molecular make-up of the fuel that is higher octane, what they add to achieve higher octane (it's not "a bunch of chemicals" added to gas to increase octane - normally (without the use of ethanol) it's hydrocarbon mixture of benzene, toluene, xylene and ethyl-benzene. Gasoline aromatics - and they are refined from low-octane petroleum products into a high-octane gasoline additive. A certain amount of BTEX is native to gasoline, it is also added to finished gasoline to boost its octane rating .......).
So it's actually other products of petroleum, normally found in gasoline anyway, that's added to raise octane, ethanol is another way.
My stuff is pages.........

 

[rafaelsmith]

I run 87....the cheaper the better.

I tried running 93 in my JK for awhile and it ran worse than with 87.

 

[Aonarch]

Run what it's rated for, 87.

As said, octane is just the fuels resistance to detonation.

116 octane would run like pure shit, even if the station called it Ultra Platinum Gas.

Now if you are in an odd situation, like the Mojave Desert, towing a trailer, maybe a higher octane would help prevent detonation or knocking.

But for 99% of us, 87 octane is what the engine is programmed for.

Now if you have an aftermarket tune that adjusts the fuel map, ignition, spark, etc that's great, run a 93 octane tune.

I'll be running the Livernois 93 tune once its released for the 2021 model.

 

[Bucephalus]

Where is 93 the same price as 87? Around Marxsachusetts 93 is always 40 cents per gallon more.

It's always like $.40 more.. But this part of Miami always had it cheaper. That stopped a week before the gas shortage...but it was selling the gas that cheap for at least the passed 8 months. I hope they do it again.

 

[Dakarider]

I use 87 most the time. They sell 85 around where I am though and has run fine with that I used a couple times. But this gas station I live near just converted from Mobil to Sinclair and they have 89 mid grade that I might use more.

 

[BT911]

21 gladiator using 87 since the day I got it. Recently it seems as the weather has gotten warmer I’m hearing a ping when accelerating slowly from a stop. Jeep seems to run fine getting decent gas mileage. I’ve taken it to the dealer and they always claim the don’t hear it. So frustrating. Am I doing any major harm to the engine by just ignoring the ping? It’s a lease so I’m not to concerned besides the fact that I don’t want to get stuck somewhere down the line because I decided not to push the issue

 

[Mr._Bill]

21 gladiator using 87 since the day I got it. Recently it seems as the weather has gotten warmer I’m hearing a ping when accelerating slowly from a stop. Jeep seems to run fine getting decent gas mileage. I’ve taken it to the dealer and they always claim the don’t hear it. So frustrating. Am I doing any major harm to the engine by just ignoring the ping? It’s a lease so I’m not to concerned besides the fact that I don’t want to get stuck somewhere down the line because I decided not to push the issue

It has to be an issue they can confirm and reproduce in order to attempt repair. Otherwise, there is no way to know if the issue is resolved. Try running higher octane gas and see if the pinging goes away. If not, just drive it until the lease is over. Follow all the manufacturer guidelines for fuel use and maintenance, and keep records. Then, If the engine does fail, they can't blame you. The dealer visits, if they actually looked at it and provided a service sheet, will show you did your part to keep it in good running order.

 

[Dan in Pasadena]

General rule of thumb is 9.3:1 and below for 87. Jeep got this one wrong. Which is why the new 3.6s ping so much.

Whose "rule of thumb"? Yours? What is "patently false" is the idea that a multi billion dollar corporation like FCA is using incompetent engineers that would specify using a lower octane fuel that would cause detonation (pinging) in tens of thousands of engines under their warranty.

PS: Mine doesnt ping at all. They shouldn't because they are computer controlled to modify timing if detonation is sensed. Unless you are lugging the crap out of a manual I don't see how they could ping for more than an instant.

 

[ShadowsPapa]

Whose "rule of thumb"? Yours? What is "patently false" is the idea that a multi billion dollar corporation like FCA is using incompetent engineers that would specify using a lower octane fuel that would cause detonation (pinging) in tens of thousands of engines under their warranty.

There's a lot of engines running 10:1 and higher compression (static compression) running "pump gas" which we describe as 87 octane - and I'm talking "old school" engines with cast blocks and heads. These days it's a matter of design as much as other things.

 

[kevman65]

I run 90 octane, because that is the only ethanol free gas I can get around here.

The MPG is up over the 87 octane, but not enough to justify the price difference.

 

[Dan in Pasadena]

There's a lot of engines running 10:1 and higher compression (static compression) running "pump gas" which we describe as 87 octane - and I'm talking "old school" engines with cast blocks and heads. These days it's a matter of design as much as other things.

Agree. It isn't me that's claiming 10:1 compression is extra high compression. It' not "low" compression but it certainly isn't like the old days hen guys would be running 12 or 13:1 on the street.

For example the mildly cammed 6.0 LQ4 in my off topic '55 Chevy truck is an iron block engine. It is 9.5 compression now. LS engines hardly qualify as "old school" and I run 87 in it all the time. It is running the Holley Dominator EFI and runs great. It's "only" making a bit more than 350-360HP and similar torque; which is fairly low for that engine. And it never pings in the least even if I bury my foot in it.

Sorry, it's dusty in the 2nd pic:

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