I ran premium (91) for a few years on my 2013 and found the fuel mileage slowing degraded over that time. So I started running what the factory recommends (87) and the fuel mileage has slowly crept back up where it should be.
With VVT and KR working to maximize performance and preventing detonation, I'm confident the engineers have squeezed as much as they're going to allow from the 3.6L motor mounted in a Wrangler - without someone tampering with the fuel/ignition tables.
We had one member here that was doing just that and he was running premium. But he really knew what he was doing...
I personally believe mine runs better on 87, obviously using Top Tier fuel. I've been using Chevron with Techron...
I'd like to see what the 3.6L does timing-wise with regular vs premium. My guess is "nothing interesting" ... but on the LTZ in my Colorado the difference is dramatic. However the LTZ is pretty modern by comparison (which has both pros and cons).
Yes, Daimler-Chrysler vehicles were noticeably very sensitive to regular vs premium, because they tried to advance the spark timing for premium. I'm guessing Fiat did not do away with the DC approach, only fine-tuned the programming.
For many engines regular is recommended, does not mean that premium is not better for performance. I run premium and I don't have a heat problem, no ticking at start, and my oil cooler has not leaked,, LOL. But my MPG sucks at about 12-13 average because of how and where I drive, not to mention lift, tires, and added weight.
Regular and Premium require different ignition timing. If you have a tuner and can tune for Premium fuel you will see better mileage and better performance. If you don’t have a tuner and run Premium on a factory tune you will likely see poorer fuel economy however it my run smoother as it is a higher grade fuel with no ethanol.
I use to run Premium with a tune in my 2008 3.8L and that made a huge difference over 87 regular and the factory tune.
I had the 3.8, now 3.6 and have used regular in both. Figured i wouldnt see enough performance or fuel mileage gain to justify the near 20 percent hike in cost around here, but wouldnt be surprised if that new 2.0L required premium.
Ethanol is a simple fact of life, beside being a oxygenator it is also a octane booster. The days of non-ethanol fuel are slowly going away.
Unless you have a tuner that calls for a specific octane run what is in the manual. If you are pinging or knocking you need to have the issue corrected as this should not happen on an otherwise healthy engine.
99% of the premium gas sold in the US has just as much ethanol as the lower octane fuel marketed by the same co. Premium fuel is determined By the octane not Ethanol content.
The tier rating is determined by the detergent additive package by the distributor at the tank farm. The fuel from the refiner's to the farm in most cases all comes through the same pipe line and is graded , blended and sorted at the farm. You can choose to buy Ethanol free gas if it is available in your area but you will pay more. Ethanol is just an additive to reduce emissions
Be careful with what you are saying unless you are sure and it's recent knowledge. Very few of you even have access to ethanol free gasoline and bumping up to premium from regular isn't going to help for many people.
Most states have no guidelines about ethanol and premium and ethanol is used, in part, to raise octane. So you're just as likely to see it in premium gas.
There are very few places here in CT that sell ethanol free and they charge an high price for it. You're not going to daily drive with it. It's also typically 94 or higher octane.
I really dislike it - I would happily pay more for ethanol free gas; I have four vehicles and a lot of small engines and I do believe they suffer for it.
Timing between 87-91 will adjust instantly, a few piston cycles, would engine make more power? , probably 2-3%, would it offset the price difference of 10-15%? - probably not.
In other words if your engine is running well on regular (no pings,hesitations, misfire) I wouldn't suggest running premium except for maybe towing, off-road. 100+ heat etc.
Normally run the regular. When out for a weekend of wheeling I fill up on premium. I feel the jeep has much better performance at lower RPMs with out knocking/tapping.
I couldn't agree more with you here. Maybe cuz I have a MT but I sure as hell notice more low end torque and less low end pinging with 89 over 87. Haven't tried 91-93 yet, don't think I need to but I will. I suggest everyone try 89+ just to try it. MT's may benefit more here. Perhaps its my 70k engine...
I treat my Jeep to ethanol free regular octane top tier gasoline. Plenty of gas stations near me with shit gas, use link below to find top tier near you.
https://www.toptiergas.com/
I run premium with 93 performance tune all summer while wheeling and towing my camper. It does not feel as sluggish. Winter, I run regular 87 tunes as I do not drive as much.
There are a few common misconceptions typically raised in these discussions, and "slower burn" is one of them (and ironically, so is "faster burn"). The octane rating is completely unrelated to the rate at which the fuel burns once correct ignition-driven combustion begins.
The other common misconception (not raised here yet) is that higher octane fuel somehow has "more energy". The octane number itself has absolutely no relation to the available energy.
The octane number is only susceptibility to premature detonation due to compression (aka knock or detonation) -- nothing more, nothing less.
I find it sort of interesting where the octane number comes from:
Octane is the abbreviated name for a chemical called iso-octane. There is something called n-heptane which is highly susceptible to ignition by compression. Heptane is the "zero point" material, meaning pure heptane's susceptibility to detonation (combustion by compression) is litreally a zero octane rating: 100% heptane, 0% iso-octane. The octane rating tells you the gasoline's equivalent behavior of that much octane mixed with heptane. Real fuel contains as little n-heptane as possible because it's so volatile. Pure n-heptane is easy to acquire -- it comes from pine trees -- so it makes a good lab reference.
So 89 octane gas means the fuel's combustion behavior is the same as 89% iso-octane mixed with 11% n-heptane. The fuel mix doesn't actually contain that much octane or n-heptane, it's just a reference number. Because it's an equivalency-reference, racing fuels can have an octane rating greater than 100 simply because chemical engineers can formulate mixtures that resist combustion by compression much better than pure iso-octane.
I run premium with 93 performance tune all summer while wheeling and towing my camper. It does not feel as sluggish. Winter, I run regular 87 tunes as I do not drive as much.
Obviously a tune will have a big effect, but all refineries produce summer and winter blends of fuels, which is a smog-related mandate from the EPA. Winter blends add chemicals to allow the gasoline to evaporate at lower temperatures, which also reduces the fuel's energy content. Summer blends are more expensive to make which is why prices go up in the summer. I've read that summer blends have about 2% greater energy potential than winter blends, on average.
Higher octane fuel is less explosive then lower octane fuels. When fuel is compressed, it becomes more explosive. In high compression engines, lower octane fuels will detonate before TDC, causing the "pinging". If you run higher octane fuel in an engine that recommends to run "regular", you are not getting better performance or fuel mileage. In fact, just the opposite. Higher octane fuel in lower compression engines will not completely burn, causing less performance and fuel mileage. I hope I explained this good enough. Bottom line, run what is recommended by the manufacturer.
Most of the time running 89 octane with a Flashpaq 87 tune. Also swapped the plugs and cables at 100k. Now at 167k and looking into replacing them again along with upgrading the coil pack.
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