Run what the manual recommends, period. I don't know why there is so much discussion about it. You're talking a couple bucks per fill up. If money is that tight, you shouldn't be buying a new Jeep. To me it's very cut and dry.
I have the 2.0 and have driven the 3.6. I'm also in Colorado at 6,000 feet elevation (and go up to 12,000 on occasion) so I've always preferred turbos if available. Assuming it's reliable, I don't think you can go wrong with the 2.0, it's quite fun to drive.
Drive them both and pick which you like best. Some like the extra low-end power of the turbo I4 and don't mind the lag. Some prefer the rev-happy nature and sound of the 3.6L. And some are so hell-bent on using a clutch pedal that the choice is made for us (like me).
But it's not cut and dry. It depends where you drive it and how. The manual says the engine is designed to run on 87 octane. It goes on to say that there will be a benefit in performance when using 91 octane in hot conditions or when towing. Putting 91 octane if you drive in winter at 5,000 ft above sea level is a waste of money. Has nothing to do with money being tight.
The altitude loss has little to do with carbs or fuel injection. The air density at 10,000 feet is less than it is as sea level - fuel injection can't change that. There is less oxygen in the air - period. Ambient air pressure at sea level is about 14.7 PSI, at 10,000 feet it drops to around 10 PSI. That's why turbos don't lose as much power at altitude as they can make up that air density deficit.
... Well then there you have it, though. It is cut and dry. 87 octane unless in hot conditions or towing. Just follow the manual.
Couldn’t agree more. I have a 2020 Rubicon and the manual states 87. No problems.
So, I'm just an unfrozen caveman, but what I do know from unfrozen caveman science is that a higher compression engine requires higher octane to prevent pre-ignition. Pre-ignition occurs because the gasoline will ignite easier at higher pressure (for a given amount of oxygen). The 3.6 is a fairly high compression engine in the Jeep. When the similar engine was used in the Pacifica, the compression ration was 10.2-1, In the Jeep it's 11.3-1. If you aren't getting any pinging, it probably wont hurt your engine or anything, but where the ignition happens (in the cylinders cycle through to full compression) will affect power. I buy the highest octane I can easily find around here: 91. I'm at altitude so it's about equivelent to 93 at lower altitudes. I'll save that for another unfrozen caveman science lesson.
Keep in mind, that Mazda engine is a direct injection system which can run higher compression ratios as compared to the "old" traditional multiport injection that our Pentastar is based on. 11.3 is pretty high for standard multiport injection. This is why guys like Livernois can extract so much more power using 93 octane - they can get a lot more advanced timing using the high octane fuel on a high compression engine like this.
