87 or 91+ octane?

[RoadiJeff]

My wife puts 87 in her 2020 Recon 2.0T. With the way she drives I doubt 91 would have any benefit for her. Plus, with gas prices the way they are lately, I'm sure she's not going to switch to anything more expensive.

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[lashlee]

Any time I fill up my wife's 2.0 JLUR I put 91 in it. She says if she gets gas at Costco she put 93 in it, but considering I spent $83 last night for 18 gallons, I may drop down to 87!

 

[shindleria235]

been doing 91/93 pretty much every fill up since i bought my 2019 2.0 in 2020. only have done 87 a few times when no high grade was available or by accident. i watch my mpg like a hawk bc of long commute and overall curiosity about the eTorque system & turbo behavior. two things I'd add here:

- 2-3 mpg drop per fill-up when using 87 after long term use of higher octane. can't speak to the computer readjusting, but this was most apparent in summer/July/August. also when I tend to do most long-trip highway driving which tends to have my best overall mpg (can squeeze out 25-28 on the dash, usually 1-2 mpg lower on receipt math).

- oil change & dealer installing a 40w oil one time made a MUCH bigger difference. like 3-5 mpg, response time noticeably more sluggish, etc. maybe makes sense for winter in a more northerly clime but in the dirty South we still get 60 deg days in February. would rather keep the mpg up, she's enough of a brick as is.

 

[SnowyJeep]

When I first got my Jeep I put a couple tanks of 87 in it. Being my first turbocharged vehicle I thought that the 2.0 had a fair bit of turbo lag. That is, until I came across this forum and read that it pretty much has none.

I was gearing up to purchase a pedal commander, but after switching to 91 the "turbo lag" went away.

As this thread indicates, 2.0T Jeep owners have great success with their choice of 87 or 91. You will not go wrong with either option. However, in my experience there is a noticeable performance gain from using 91 octane.

 

[four low]

I have been doing the cool/ cold weather with 87 ; hot weather will see return to 90, non- ethanol.
I have been getting good mpg and performance with the 87, the difference in price per gallon is $.70 .

 

[jeepoch]

@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

 

[Boatbuilder88]

87 octane in my 2019 2.0T. I've tried 93 and don't notice much (any?) difference. Plus, the oil companies are already getting enough of my money.

 

[Devil6Dog]

@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

Thank you for taking the time to explain this. I was not aware and because of this will continue to use higher octane 91

 

[SaintNick]

Now that I know I can run 87 the 2.0 is back on the table. I'm going to look at a Sarge Green 2 door Willys with the 2.0 tomorrow.

 

[Shibadog]

Now that I know I can run 87 the 2.0 is back on the table. I'm going to look at a Sarge Green 2 door Willys with the 2.0 tomorrow.

and you’ll be fine with the 87 stuff. Here today 93 premium is 92 cents/gallant higher than 87. 91 is $49 cents a gallon higher. If the Wrangler 2.0 required “premium” I wouldn’t own one.

 

[BDinTX]

The question of "Which octane should" falls square in the question category of:
"It doesn't matter what you pick, you are wrong (and sometimes dumb)"

The most common answer is "There are eleventeen different threads on this topic, you should do a search"

Another controversial question: "What is the best oil?" has the top position on lock and shows no indication of being unseated.

That question is closely followed by "Is 2-door vs 4-door better?" There are only six 2-door owners but they are extremely vocal.

Lagging a bit behind that is "Should I regear for 37s" followed closely by "What gear oil should I use".

Edit: The "which engine should I chose - 2.0T vs 3.6 ?" is something the commoners like to squabble over, because all the true playes know the 392 is where its at. (thanks @Trini for the reminder)

Don't even broach the topic of angry grills or larger than 18" wheels because you might get doxxed.

You're probably a hoot at family gatherings - talking about religion and politics...

Seriously - just joking, smiley face to prove it : )
(except the part about angry grills and wheels)

I've tried all octanes, noticed no difference, so generally use 87 unless I'm about to hit the trail, then I tend to put in 91.

*** I have no evidence to support any of these statements much less my own opinion so please don't ask for evidence of such.

 

[Trini]

The question of "Which octane should" falls square in the question category of:
"It doesn't matter what you pick, you are wrong (and sometimes dumb)"

The most common answer is "There are eleventeen different threads on this topic, you should do a search"

Another controversial question: "What is the best oil?" has the top position on lock and shows no indication of being unseated.

That question is closely followed by "Is 2-door vs 4-door better?" There are only six 2-door owners but they are extremely vocal.

Lagging a bit behind that is "Should I regear for 37s" followed closely by "What gear oil should I use".

Don't even broach the topic of angry grills or larger than 18" wheels because you might get doxxed.

You're probably a hoot at family gatherings - talking about religion and politics...

Seriously - just joking, smiley face to prove it : )
(except the part about angry grills and wheels)

I've tried all octanes, noticed no difference, so generally use 87 unless I'm about to hit the trail, then I tend to put in 91.

*** I have no evidence to support any of these statements much less my own opinion so please don't ask for evidence of such.

You forgot to add 3.6 vs 2.0

 

[Heimkehr]

Yea, I know folks say the get more power, better mpg’s etc on 93, but I truly wonder if that’s real or placebo effect.

My JLU has been fed 91+ since the day I took delivery. No complaints.

 

[jmr]

If you want to see what happens running 87 vs premium. Try loading a OBDII app on your phone and a Bluetooth wifi connector in the OBDII port. I did and found it gave more timing and boost with premium vs 87 regular. The engine controller module will pull back timing and boost when it senses engine knock. It's self preservation mode for the engine.

 

[JeepFiend]

The question of "Which octane should" falls square in the question category of:
"It doesn't matter what you pick, you are wrong (and sometimes dumb)"

The most common answer is "There are eleventeen different threads on this topic, you should do a search"

And now twelfthteen

Another controversial question: "What is the best oil?" has the top position on lock and shows no indication of being unseated.

Amsoil. Done and done.

That question is closely followed by "Is 2-door vs 4-door better?" There are only six 2-door owners but they are extremely vocal.

Jeeps are 2 door, SUVs are 4 door.

Lagging a bit behind that is "Should I regear for 37s" followed closely by "What gear oil should I use".

You should always regear, the size of the tire only dictates how much you regear

Edit: The "which engine should I chose - 2.0T vs 3.6 ?" is something the commoners like to squabble over, because all the true playes know the 392 is where its at. (thanks @Trini for the reminder)

"all the true playes know the 392 is where its at." That statement says it all.

Don't even broach the topic of angry grills or larger than 18" wheels because you might get doxxed.

Only get 18" wheels if they're spinners, then it's a whole different ballgame

You're probably a hoot at family gatherings - talking about religion and politics...

Seriously - just joking, smiley face to prove it : )
(except the part about angry grills and wheels)

? ????

I've tried all octanes, noticed no difference, so generally use 87 unless I'm about to hit the trail, then I tend to put in 91.

*** I have no evidence to support any of these statements much less my own opinion so please don't ask for evidence of such.

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