87 or 91+ octane?

[COJeeper]

I’ve treated mine as I have with any turbo or supercharged vehicles I’ve ever had. I’ve ran 93 since day one. On average it only cost me $3-$5 more a tank to use 93 instead of 87.

That's true. Costco is .36 different between 85/91 and .36 x 21 gallons = $7.56.

However, with my natural gas bill over doubling, cost of milk at $8.49/gallon, a head a freaking iceberg lettuce at $2.19.... I need to save that $7.56 just to survive! racist times we're living in

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[COJeeper]

I wish someone had access to the means to qualitatively test this on a dyno or a track. I'd love to know how much more power is available with a higher octane fuel. That way I could decide if it was worth paying extra at the pump.

Fixed if for ya.

Evereyone has access to a chassis dyno. It would be easy. Pump the tank, put in 91. Run it and get the corrected numbers. Pump the tank, put in 87 and repeat. Just do a search and you'll find one in the area. Like anything else, it costs money and that's what stops people from doing it.

Eveeryone has access to a drag strip. Find a local one that has a test and tune night. Do a few runs with 91. Pump the tank and repeat with 87. Make sure that the weather has not changed much as that will change times. I used to run a NHRA Super Comp Dragster, so I know that weather can make a difference. Like above, that takes money.

I tried. I contacted two shops out here in CO and neither responded. I can just assume they got the email, saw Jeep Wrangler, and instantly deleted it thinking, "we race honda civics here, we go VROOM VROOM FAST with LEDs on the ground, we're fast and furious!"

I really wanted to know if it made a difference and how much and willing to pay a reasonable amount to find out.

 

[BasherXt]

That's true. Costco is .36 different between 85/91 and .36 x 21 gallons = $7.56.

However, with my natural gas bill over doubling, cost of milk at $8.49/gallon, a head a freaking iceberg lettuce at $2.19.... I need to save that $7.56 just to survive! racist times we're living in

completely agree 100%. Everything has gone nuts. I do have some fuel rewards accounts, that’s the only way I have been able to justify to continue to use 93. If I didn’t I’d be using 91 or maybe even 87. Or getting a bicycle

 

[Chance_P]

I use 91. I was using 87 briefly when I first got the 2.0, but I started having issues when going 75+ on the highway so I switched and no more problems

 

[jonyothan]

I’ve treated mine as I have with any turbo or supercharged vehicles I’ve ever had. I’ve ran 93 since day one. On average it only cost me $3-$5 more a tank to use 93 instead of 87.

Same here. everyone running 87 will have to do a carbon blast way sooner

 

[diesel_dave]

Is there any agreement here whether these will need a periodic "Italian tuneup"? My wife has the 2.0 and she drives like an old lady. Probably never gets over 2,000 RPM. Haha.

I have a 4xe and I drive the piss out of it so it sees plenty of RPM, boost, etc.

Should I "borrow" her Jeep once a month or don't worry about it?

 

[Heimkehr]

Is there any agreement here whether these will need a periodic "Italian tuneup"? My wife has the 2.0 and she drives like an old lady. Probably never gets over 2,000 RPM.

Should I "borrow" her Jeep once a month or don't worry about it?

Click
3rd sentence of the 2nd paragraph.

 

[jjvincent]

Is there any agreement here whether these will need a periodic "Italian tuneup"? My wife has the 2.0 and she drives like an old lady. Probably never gets over 2,000 RPM. Haha.

I have a 4xe and I drive the piss out of it so it sees plenty of RPM, boost, etc.

Should I "borrow" her Jeep once a month or don't worry about it?

It's actually a design issue for gunked up intakes. Some DI engines suffer from it, yet others do not. Same for IDI engines.

For example, I see the Family Taxi all of the time. It's typically a Chevy Equinox with the DI 4 cyl in it. It never gets top tier premium gas. It usually goes way past it's oil changes. Plus, it never gets driven hard. Those you never see misfire codes due to gunked up intakes.

Then you see the same scenario with a VW Tiguan and in the same period of time, it has a gunked up intake. Then you'll see another Tiguan where the owner has maintained with the best of the best and for fuel, top tier highest octane they can get. Yet they get a gunked up intake.

Then you have Grandpa driving a Cadillac with a DI motor in it. It probably never sees over 2K rpm. He always sticks in the best gas on the planet and same for the oil and usually gets it changed every 2K. No gunked up intake.

Then there's like the Equinox but replace that with other brands and they seem to do fine, yet others do not. People with SUV's are not like Jeep owners who use only the best of the best and not treat it like an appliance. With that, only time will tell if the Jeep messed up on the crankcase ventilation.

Audi had this problem starting in 1984 with the 5000. They changed the crankcase ventilation and even though they were IDI, the intake gunked up. Thus they ran too lean on startup and backfired like crazy. It got so bad, Audi would fix it by walnut shelling the intake system and a new designed crankcase vent system. Problem went away.

As for the "Italian tuneup" that was because back in the day engines ran too rich and we had that garbage leaded fuel. The combustion chamber would cake up with carbon and so would the plugs. I ran into this with Porsche 911's back in the day and it was really bad with the MFI engines. They even had a special plug for those flat 6's to try to keep them from fouling. Carb motors were not much better. Best part was those plugs were only $12 ea back in the 80's. Now they are over $40 ea. I can tell you, just going to unleaded now just has the plugs looking the typical coal black, No more carbon buildup.

 

[diesel_dave]

It's actually a design issue for gunked up intakes. Some DI engines suffer from it, yet others do not. Same for IDI engines.

For example, I see the Family Taxi all of the time. It's typically a Chevy Equinox with the DI 4 cyl in it. It never gets top tier premium gas. It usually goes way past it's oil changes. Plus, it never gets driven hard. Those you never see misfire codes due to gunked up intakes.

Then you see the same scenario with a VW Tiguan and in the same period of time, it has a gunked up intake. Then you'll see another Tiguan where the owner has maintained with the best of the best and for fuel, top tier highest octane they can get. Yet they get a gunked up intake.

Then you have Grandpa driving a Cadillac with a DI motor in it. It probably never sees over 2K rpm. He always sticks in the best gas on the planet and same for the oil and usually gets it changed every 2K. No gunked up intake.

Then there's like the Equinox but replace that with other brands and they seem to do fine, yet others do not. People with SUV's are not like Jeep owners who use only the best of the best and not treat it like an appliance. With that, only time will tell if the Jeep messed up on the crankcase ventilation.

Audi had this problem starting in 1984 with the 5000. They changed the crankcase ventilation and even though they were IDI, the intake gunked up. Thus they ran too lean on startup and backfired like crazy. It got so bad, Audi would fix it by walnut shelling the intake system and a new designed crankcase vent system. Problem went away.

As for the "Italian tuneup" that was because back in the day engines ran too rich and we had that garbage leaded fuel. The combustion chamber would cake up with carbon and so would the plugs. I ran into this with Porsche 911's back in the day and it was really bad with the MFI engines. They even had a special plug for those flat 6's to try to keep them from fouling. Carb motors were not much better. Best part was those plugs were only $12 ea back in the 80's. Now they are over $40 ea. I can tell you, just going to unleaded now just has the plugs looking the typical coal black, No more carbon buildup.

Thanks for the comprehensive response! Follow on question is how have 2.0s been with gunk buildup in the intake?

 

[jjvincent]

Thanks for the comprehensive response! Follow on question is how have 2.0s been with gunk buildup in the intake?

Wait and see or search for "misfire". When they gunk up, they will go beyond the threshold for misfires (it's counted per cyl) and then when it does, it throws a code. I check my misfires and so far, no more than 1 or 2 for a drive cycle. I don't know what the threshold is but on many cars, it's around 30-40. The way that's measured is they count the speed of the teeth on the crank sensor for each pulse. So if #1 misfires, the crank spins slower on that pulse then speeds up on the next cylinder that fires. Thus, it is counted as a misfire. If you just unplug a coil pack and start it, it feels rough. That's the crank slowing down and speeding up every two revolutions.

For modern engines, it's more critical and picks up small misfires.

 

[Heimkehr]

If you just unplug a coil pack and start it, it feels rough.

Some years ago, I experienced a coil pack failure on a new VW Golf. It idled as roughly as I'd guess an engine could do while still running.

The defective part was quickly and correctly replaced under warranty, and I filed away the memory as something to consider if or when I ever experience similar running conditions in another vehicle.

 

[8ball]

@NJbeachbum,

This topic seems to come up (very) frequently. Unfortunately the choice of fuel is and likely will always be, rather subjective. This is due to many factors. First is probably cost followed closely by performance, even if just perceived.

Today's engine controllers do a remarkably good job of reacting and adjusting the combustion equation based on both fuel quality and type. It does this dynamically for every combustion event. Unfortunately what most people don't take into account is the real potential for 'knock' even if imperctable by the driver. Knock is a condition that occurs when any combustion occurs before the piston achieves a position called Top-Dead-Center (TDC). When this happens, the explosive energy in the piston works against forward crankshaft rotation and actually then negatively (retards) engine output power.

However, and most importantly, when this pre-detonation occurs, potentially violent mechanical forces are created causing vibration (hence called knock). Any knock whatsoever, of any kind is detrimental to the reliability and longevity of the engine. All of the piston's sliding surfaces, especially it's rings can prematurely wear or even be damaged leading to eventual loss of compression.

Lower octane fuels tend to promote knock because octane is NOT a measure of a fuel's energy content, but rather its flashpoint. Fuel combusts at a particular temperature and pressure threshold. The higher the octane, the more consistent this temperature and pressure flashpoint becomes. Therefore, the easier it is for the spark timing algorithms to predict and manage optimum location of the piston to only produce positive (not negative) rotational thrust and thus lowering the possibility of knock.

Furthermore, even though the engine control computer will sense knock and react to try and prevent any further events, a knock event already HAS happened. Recall, any knock (whatsoever) is DETRIMENTAL. The idea then is to try to prevent any knock from occuring in the first place. A lower octane fuel will only decrease the probability of preventing knock all together.

I have previously posted (in rather good detail) more about this in other posts. Please refer to:

https://www.jlwranglerforums.com/forum/threads/question-about-3-6l-v6.89074/#post-1855152

In summary, lower octane fuels are offered, and even recommended, just to lower the overall cost of vehicle ownership. But using the lower octane offerings only increases the potential and higher probability of knock conditions in general. Higher octane fuel will lower the chances for any knock event to occur in the first place. Thus greatly improving engine lifetime reliability and longevity.

Again, everyone's opinions will always be somewhere across the entire spectrum for any number of various subjective reasons. However, from the perspective of overall best long term performance, independent of cost, higher octane fuel is always your Engine's best friend.

Happy motoring...
Jay

Great explanation. It’s not performance or cost savings for me but, long term reliability. I didn’t spend 60K on a Jeep to put the cheap stuff in it.

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