91 vs 87, real difference?

Ksvette

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So.....here is what I want to know. Anyone have some good solid data on if it makes a difference? Jeep said 91, then I guess changed and said 87 is good unless really hit or towing, then 91.

Let's assume we all know premium isn't automatically better. Octane helps with knock, and if not needed then is a total waste.

Also, does turbo have an effect on this? My first forced induction. My other toys have 8 cylinders, do this is a new world for me lol.

So go.... convince me to use 91, or convince me 87 is good.
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Cmcclaflin31

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In theory, turbo engines will have more compression in the cylinders. (Not saying this is always the case.) Typically with higher compression, you want higher octane. As for swaying you one way or the other, my owners manual RECOMMENDS 91, doesn't say I NEED 91. It also says if you want to, you can use 87. The way I look at it is it's programmed to run 91, but it can register that you're not running 91 and will adjust accordingly. My thoughts are if I use 91, which is the recommended grade, then there's a possibility I will have a slight increase in power and/or fuel economy. This wouldn't really matter about fuel economy since premium is far too much more than 87 to worry about fuel economy and price. However if I'm going on a long trip, I'd like to be able to travel a little further instead of having to fuel up. If it actually boosts gas mileage, I don't know. I've never fueled up with 87, only 91 or 93. If the manual says it recommends that type of fuel, I like to use it.
 

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So.....here is what I want to know. Anyone have some good solid data on if it makes a difference? Jeep said 91, then I guess changed and said 87 is good unless really hit or towing, then 91.

Let's assume we all know premium isn't automatically better. Octane helps with knock, and if not needed then is a total waste.

Also, does turbo have an effect on this? My first forced induction. My other toys have 8 cylinders, do this is a new world for me lol.

So go.... convince me to use 91, or convince me 87 is good.

Previously addressed and can be located with the forum search. See post 25 here by @CatskillsAlex - https://www.jlwranglerforums.com/forum/threads/what-octane-is-everyone-running.15481/page-2
 

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Like the manual states...........lower octane can be used with reduced performance.

Modern engines will retard timing and adjust to reduce the possibility of engine knock/ping.
How noticeable it is depends on driving conditions. A winter day with an empty jeep vs. a hot day pulling a camper with a loaded jeep you will likely notice a performance difference.
 

ztobro

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Personally I run 91 or 93, whatever is available. I think it runs smoother, turbo comes on sooner and it accelerates faster. Could it all be in my head? Definitely. Have a noticed slightly better fuel economy with it? I have, nothing crazy but 1-2 mpg more on average helps. I’ll use 87 in a pinch but seeing how the manual recommends using 91 or higher that’s what I’m going to stick with. :like:
 
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Ksvette

Ksvette

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Interesting, and I certainly agree on compression (again, my V8s mostly all require premium due to compression). Just u hat tried both, and really don't see much difference.
 
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Ksvette

Ksvette

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Jesus the lack of knowledge when it comes to forced induction is sad.

Put premium in it. You bought a $50k car why are you trying to save five dollars a fill up.
Wow easy there. I have used a bunch of both. I own three vettes, all REQUIRE premium, not a recommend thing. No premium equals knock. My cadi can run on anything. If it is needed, no issue. If not, why do it? Obviously if pulling the camper, use premium. But just daily? Why, if not needed. If needed yes. But no need to be an ass.
 

turbosix

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Wow easy there. I have used a bunch of both. I own three vettes, all REQUIRE premium, not a recommend thing. No premium equals knock. My cadi can run on anything. If it is needed, no issue. If not, why do it? Obviously if pulling the camper, use premium. But just daily? Why, if not needed. If needed yes. But no need to be an ass.
Your vettes will pull timing and be just fine unless they're c4s.
 
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Ksvette

Ksvette

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Your vettes will pull timing and be just fine unless they're c4s.
One is c4. One is a c3 with a c4 lt1 I stuck in it. The other is a modified c6. Prior to that, a modified c5. Has to be 91 or ping. C6 can still pull timing yes, but will run like crap. I haven't noticed that with the Jeep. Hence the question.
 

turbosix

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One is c4. One is a c3 with a c4 lt1 I stuck in it. The other is a modified c6. Prior to that, a modified c5. Has to be 91 or ping. C6 can still pull timing yes, but will run like crap. I haven't noticed that with the Jeep. Hence the question.
Yeah the older stuff will try and fail. I have a grand national that will try but you'll end up with a blown head gasket in about one second of a WOT pull.

The new stuff is much better at saving itself.

I just don't see the point in getting a nice new turbo car and throwing the cheap shit in it unless you're in the boonies and there's nothing else available.
 
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Ksvette

Ksvette

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Yeah the older stuff will try and fail. I have a grand national that will try but you'll end up with a blown head gasket in about one second of a WOT pull.

The new stuff is much better at saving itself.

I just don't see the point in getting a nice new turbo car and throwing the cheap shit in it unless you're in the boonies and there's nothing else available.
Mostly it is q daily, not a toy. It will get what it needs to perform the most efficient (based on mileage, engine life, and cost). I don't care if it is fast, I got other stuff for that. It just seems a little odd how jeep jut it. Mostly if over 95 been getting premium. If pulling, definitely premium (those two instances are displayed in manual as a must I think).

When premium is within about .30 for it, premium. But some places want as much as a dollar more...then 87. It does get a majority of top tier gas for the detergent. When not top tier, definitely 91. It won't make up for the missing detergent, but hopefully a little less nasty build up if timing being used to full advantage.

I guess the curiosity is, how much timing is being pulled? And how much does that effect turbo (as again, first boosted car)? I know on my ls2, if timing bus pulled, it is a lot and I can certainly tell. On this, I haven't seen much. Maybe a bit more lag in the turbo, but I also wonder if that is in my head as I am looking for it.

P.s. grand national.... sweet ride.
 
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