What octane gas do you guys run

[Trailman]

PSA for those traveling through Colorado, Wyoming, etc - you should still use 87 here, even though "Regular" here is 85. The 85 rule is a leftover from carburetor days, where it made sense to have a lower octane given lower oxygen density (if I understand correctly). Modern fuel injected systems are already compensating for environmental conditions, however, and expect that you're using 87 octane regardless of altitude, etc.

Would love someone like @ShadowsPapa 's confirmation (or correction).

In any case, to the original question, I use 87, despite lower or higher options.

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[Klutch]

PSA for those traveling through Colorado, Wyoming, etc - you should still use 87 here, even though "Regular" here is 85. The 85 rule is a leftover from carburetor days, where it made sense to have a lower octane given lower oxygen density (if I understand correctly). Modern fuel injected systems are already compensating for environmental conditions, however, and expect that you're using 87 octane regardless of altitude, etc.

Would love someone like @ShadowsPapa 's confirmation (or correction).

In any case, to the original question, I use 87, despite lower or higher options.

I live in Colorado at over 6,000 feet above sea level. The 85 octane works fine. Whether or not the engine is carbureted is irrelevant. Yeah, the user's manual says to run 87 or higher. If running 85 actually caused a problem, hundreds of thousands of Colorado vehicles would have problems. They don't.

Like Shadow's Papa, I'm into classic cars. I've been driving 1960s and early 1970s cars for over 40 years. Yeah, I know what pinging is and my Pentastar has never pinged; not once.

Modern engines have electronic fuel injection and spark control. They quite literally change the air/fuel ratio on the fly. They quite literally change the ignition timing on the fly. They have knock sensors. So, if a Pentastar was to ping, the engine computer would make changes to stop that pinging. If your Pentastar is pinging, it's got a serious problem that has nothing to do with octane.

While the Pentastar engine has seemingly high compression, it doesn't require high octane fuel because it has aluminum cylinder heads which do a better job of removing heat from the combustion chambers than old-fashioned iron. The combustion chamber is also designed to prevent pinging/detonation. (The 351 Cleveland in my Mustang also has combustion chambers which resist pinging/detonation.) This combined with the computerized controls mentioned above keep it from pinging. I know people claim they get better MPGs from higher octane gas. I won't call them liars, but physics does not support such a situation.

Bottom line is higher octane fuel in a Gladiator won't do anything other that cost you more money. But it's your truck. If you feel better about spending extra money on gasoline, go for it.

 

[ShadowsPapa]

PSA for those traveling through Colorado, Wyoming, etc - you should still use 87 here, even though "Regular" here is 85. The 85 rule is a leftover from carburetor days, where it made sense to have a lower octane given lower oxygen density (if I understand correctly). Modern fuel injected systems are already compensating for environmental conditions, however, and expect that you're using 87 octane regardless of altitude, etc.

Would love someone like @ShadowsPapa 's confirmation (or correction).

In any case, to the original question, I use 87, despite lower or higher options.

Thanks for the heads-up on CO fuel. I plan on visiting that fine state in early June for the AMO show/swap meet. Colorado Springs. The thing about buying fuel in that area - for visitors anyway, is that I may fill up there and then drop down to lower elevations while still having a tank of your "regular". Then I'd be running 85 at lower elevations.
Since the air is "thinner" at high elevations you CAN run lower octane there because you will have less air to "compress". But if you plan on dropping in elevation, I high recommend getting 87.
In short - 85 makes sense in the thinner air - so if you LIVE and DRIVE there, it's fine because you will be running lower chamber pressures.
But if you drive in lower elevations or fill up and drive away from Denver, for example, use 87.
It's all because of the lower air density resulting in lower chamber pressures in the engine, ratio be damned.

Here's another fun thing about compression ratios - when a modern engine (or legacy engine for that matter) talks compression ratio, they are talking STATIC theoretical compression ratio. That means if the engine is 100% efficient at pumping, you get a full chamber but not over full, then run the piston up and compress that air with no loss, you get that number, say it's 11:1
You take a volume of air, and compress it, and you compare the volume before and after.
But engines aren't perfect pumping machines - in fact they can run MORE than 100% or less, depending on variables like cam timing, LSA, valve opening, the number of degrees a valve is open compared to closed, intake runners and more.
For example - I had a 1970 Javelin 390 that had detonation issues - it finally developed a miss and I noted the crankcase didn't pull a vacuum. I opened it up and found number 5 piston busted. #2 didn't look so hot either. I put 1971 larger chamber heads, better pistons, etc. and lowered the compression ratio from about 10:1 to a bit over 9:1 - I forget the exact numbers now.
I STILL had some minor ping under certain conditions. I was scratching my head - what the heck was going on? I chatted with some racing guys, hard core fellows, and we talked about my cam choice and other factors - the Edelbrock intake, cam timing and such - come to find out I had LOWERED the static compression ratio but built an engine that had a high dynamic compression ratio. That meant that over certain RPM it was actually running higher than 10:1 compression due to the cam and increased intake efficiency.
It wasn't all due to the build though - I later put in a professionally cleaned radiator, a 3 row core instead of the stock 2 row core rad and it helped a ton. The engine never over-heated under normal conditions but apparently I had some hot spots helping cause ping.
OK, all that brings this up-
VVL, VVT.
In effect, these engines have a system that can on the fly impact your dynamic compression ratio. They can change the valve lift and the valve timing and it's the same thing as if I swapped cams in one of my cars depending on my driving conditions.
Advancing a cam builds more low-end torque and increases throttle response. 4 degrees advance bring the peak torque in about 200 RPM sooner. If you are a Jeep rock crawler with a 4.0 - try that trick.
Retarding the cam timing builds more high RPM power. That's why engine builders seeking performance are concerned about degreeing the cam.
Anywho - modern engine like the 3.6 will actually have different dynamic compression depending on the valve lift and valve timing. That can impact detonation tendency.
Static compression is only a fraction of what can or will happen.
Cam timing, valve lift, intake efficiency, exhaust efficiency and many other factors come into play. It's not as simple as it once was - and actually, it never was all that simple. You can have a high static compression ratio and your cam sucks and you end up with low dynamic compression, or the other way around.

 

[ShadowsPapa]

I live in Colorado at over 6,000 feet above sea level. The 85 octane works fine. Whether or not the engine is carbureted is irrelevant. Yeah, the user's manual says to run 87 or higher. If running 85 actually caused a problem, hundreds of thousands of Colorado vehicles would have problems. They don't.

Like Shadow's Papa, I'm into classic cars. I've been driving 1960s and early 1970s cars for over 40 years. Yeah, I know what pinging is and my Pentastar has never pinged; not once.

Modern engines have electronic fuel injection and spark control. They quite literally change the air/fuel ratio on the fly. They quite literally change the ignition timing on the fly. They have knock sensors. So, if a Pentastar was to ping, the engine computer would make changes to stop that pinging. If your Pentastar is pinging, it's got a serious problem that has nothing to do with octane.

While the Pentastar engine has seemingly high compression, it doesn't require high octane fuel because it has aluminum cylinder heads which do a better job of removing heat from the combustion chambers than old-fashioned iron. The combustion chamber is also designed to prevent pinging/detonation. (The 351 Cleveland in my Mustang also has combustion chambers which resist pinging/detonation.) This combined with the computerized controls mentioned above keep it from pinging. I know people claim they get better MPGs from higher octane gas. I won't call them liars, but physics does not support such a situation.

Bottom line is higher octane fuel in a Gladiator won't do anything other that cost you more money. But it's your truck. If you feel better about spending extra money on gasoline, go for it.

THANK YOU for the reminder - yes, aluminum heads. Aluminum heads resist detonation. You can have the exact same engine, and all you do is swap to aluminum Edelbrock heads, same compression ratio, same everything else, and they won't ping.
Fast burn chambers resist detonation because it takes time to build up the pressure - the charge is all burned because the cornered gases can self-ignite.
Nice - a 351C Mustang. Great engines for sure.
The VVT and VVL of the Pentastar will impact things as well - move the torque band, impact throttle response and change dynamic compression ratio.

And on the 85 - it's a matter of air density up there like you said.

 

[Trailman]

I live in Colorado at over 6,000 feet above sea level. The 85 octane works fine. Whether or not the engine is carbureted is irrelevant. Yeah, the user's manual says to run 87 or higher. If running 85 actually caused a problem, hundreds of thousands of Colorado vehicles would have problems. They don't.

Like Shadow's Papa, I'm into classic cars. I've been driving 1960s and early 1970s cars for over 40 years. Yeah, I know what pinging is and my Pentastar has never pinged; not once.

Modern engines have electronic fuel injection and spark control. They quite literally change the air/fuel ratio on the fly. They quite literally change the ignition timing on the fly. They have knock sensors. So, if a Pentastar was to ping, the engine computer would make changes to stop that pinging. If your Pentastar is pinging, it's got a serious problem that has nothing to do with octane.

While the Pentastar engine has seemingly high compression, it doesn't require high octane fuel because it has aluminum cylinder heads which do a better job of removing heat from the combustion chambers than old-fashioned iron. The combustion chamber is also designed to prevent pinging/detonation. (The 351 Cleveland in my Mustang also has combustion chambers which resist pinging/detonation.) This combined with the computerized controls mentioned above keep it from pinging. I know people claim they get better MPGs from higher octane gas. I won't call them liars, but physics does not support such a situation.

Bottom line is higher octane fuel in a Gladiator won't do anything other that cost you more money. But it's your truck. If you feel better about spending extra money on gasoline, go for it.

I have two vehicles - a VW Golf and the Gladiator. The JT is much newer. When we bought it I decided to put 87 in it (following manufacturer recommendations). In the Golf we put in 85 (but yes, it also is recommended to use 87, and we ignore that).

I agree with you I've never had a problem with 85. But there is a decent amount of literature out there saying that modern vehicles do not benefit from the 85 rule. Again - I do use 85. I'm just pointing out that the manufacturers and the EPA say to use 87.

Denver Post article for instance.

This article covers more sources, and better.

 

[cb4017]

I ran 87 octane in my 2019 JLU and now my JT. They both ran fine and I never noticed any pinging, even in the summer when hauling my small travel trailer. Been driving since 1970 so yea, I know what to listen for.

I have tried 91 octane and did not notice any benefit. The only fuel I tried where I did notice a benefit was 87 octane ethanol free. About a 1.5-2 mpg increase. Unfortunately ethanol free is very hard to find around here and expensive.

 

[Klutch]

I have two vehicles - a VW Golf and the Gladiator. The JT is much newer. When we bought it I decided to put 87 in it (following manufacturer recommendations). In the Golf we put in 85 (but yes, it also is recommended to use 87, and we ignore that).

I agree with you I've never had a problem with 85. But there is a decent amount of literature out there saying that modern vehicles do not benefit from the 85 rule. Again - I do use 85. I'm just pointing out that the manufacturers and the EPA say to use 87.

Denver Post article for instance.

This article covers more sources, and better.

Interesting. Thank you.

 

[Sazabi19]

I thought if a station only had 91/93 you could still select 87 but it gave you what it had. Weird.

I only run leaded gas through my truck, I like the way the emissions smell better. I also put in a bit of castor oil for the flavor.

In all seriousness you won't hurt your truck running the better gas, you'll probably just end up running a bit rich. The good news is that you may have have a bit more in the detergent dept running through there, so that's always good.

 

[ShadowsPapa]

I thought if a station only had 91/93 you could still select 87 but it gave you what it had. Weird.

I only run leaded gas through my truck, I like the way the emissions smell better. I also put in a bit of castor oil for the flavor.

In all seriousness you won't hurt your truck running the better gas, you'll probably just end up running a bit rich. The good news is that you may have have a bit more in the detergent dept running through there, so that's always good.

Follow the biodiesel VW guys around here - smells like your favorite fried food HAHA.
Maybe should add some omega 3s to it - pop in some fish oil pills. Make it run smarter, too.

Just as sort of a post script - I find it interesting that compression ratio enters into this since the LS engines, like the LS3, and depending on which generation of this, that or the other thing, displacement and so on - in the 2000s ran 10.7 and even 10.9 ratios, 87 octane............ that was over a decade ago.

 

[PAULIEWANKENOBI]

I have run 87, 89, 93 in both my gladiator and my wife's 2020 grand Cherokee with 3.6l in it. I can tell you BOTH of the vehicles ping with 87. I usually run 89 in both, and my wife filled both with 87 when I was away(without my knowledge) and I heard pinging in my truck with the top down doors off, and hers with windows open. I actually asked her what she put in and didn't know till she told me. So in MY experience 87 pings, 89 and above doesn't. Just my 2 sense.

 

[Rubiwoo]

I have zero ping on 87 octane in mine and I get good gas mileage.

I am down in Mexico right now and I noticed our JT pings at low ram's like crazy. I never noticed it before while in the States. I will test after we get back in the States with a couple fillups

Might be the cheap crap gas. The stations say they are Arco or Chevron, but I have a picture of a Pemex fuel truck at the Chevron that says otherwise.

 

[j.o.y.ride]

I topped off my half full 87 tank with 91 and the pre-detonation that was reliably there basically disappeared. And this sort of strained sound the engine would make at high speeds was suddenly just smooth sounding. The wife noticed both without me telling her I had used 91. I almost exclusively use the Chevron in town.

Tank was about 60% full so it would be like a net 88.6 octane.

 

[ShadowsPapa]

Filled it up with Fleet Farm regular (87) again this AM - it was a reasonably quiet day, little wind and part of the time we were driving with what wind there is, all the hills, accel, decel for traffic and so on, engine quiet. The only noise was when I'd reach an slight incline and the thing would drop down a gear (this does a lot of back and forth shifting indicating it's really under a load at those lower RPMs in the upper teens) and it was quiet except for the sound of the air intake. When it downshifts you can hear is sucking in air a lot like my 4.0 does.
We must own rare Jeeps all the time or our gas is better here - even at Fleet Farm, Casey's, whatever, never hear any ping at all and my wife can hear a whisper clean across the house on the other floor or hear one of our cats meow in another room with the door closed. You can't say a thing to anyone without her hearing it. The girl has ears like a hawk. "What was that sound" I used to hear all the time. She accused one of my cars of having a tiny squeak like a mouse and no one else could hear it - she did. I must have finally fixed whatever it was without knowing it - she says the car is quiet now.

 

[CapnStereo]

I am NOT a mechanic, and quite frankly don't know what the hell I am talking about. I do know what my mechanic and a couple others have told me, and solved an issue in my 08 wrangler. In my case, I was told it's not the octane, but the detergents. I was burning a quart of oil ever 2k in the wrangler, and my mechanic flushed the engine (65k on it) with Seafoam, and told me to periodically run 93 top tier, and a can of seafoam. Naturally, I overdosed on the advice, and ran high octane from then on, and periodically added seafoam. Never burned a quart of oil between changes (every 5k) after that. My friend works on boats, and swears my mid grade and 91, says it keeps valves and other things clean. That's what he uses in his truck. Again, detergent, no mention of power. So, with my JT, I alternate between the hi and 87, using top tier. No pinging, but again, I would not know what to listen for. And mileage has been 22+

Also, I enjoy the discussion, but BE NICE! Knowledge and opinions are important to share. Leave the slights for the less informed.

Best,

Cap

 

[Lucrob]

I’m curious to what all you guys run? I have always ran 87 since I bought it. However with the gas pipeline issue I was only able to find 93 the other day and it seemed like the truck liked it better. I don’t know if it was in my head or not but truck seemed to run smother and had more pick up. Do you guys ever run anything over 87

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