What gas are you using?

[DanW]

My JK's 3.8 can tell the difference in quality of gasolines. With Top Tier, it runs great. With cheap gas (non-Top Tier) it gets deposit buildup and starts to ping after about 3 or 4 tank fulls. I then have to run a tank of V-Power or use a bottle of Techron and do a few Italian tune-ups to clean it out and stop the ping.

On Shell 87, it never gets the build-up and never pings. I've not seen it do it on any other Top Tier fuel, either. But Kroger....Yep. Like I said, 3 or 4 tankfulls and it is a pingin' away at low rpm with a load on it.

It also runs better on ethanol free gas. You can feel the difference with 91 octane Sunoco recreational fuel that is ethanol free.

I can't tell a difference with any of them in my 3.6. It runs perfectly on all fuels. But I only run non Top Tier if I have no choice. Mostly, it gets Shell 87.

But that old 3.8 is very sensitive to fuel quality. She just turned over 157k miles today. So I speak from vast experience with it.

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[FloridaMan655321]

If I'm at a Mobile/Chevron station, I'll get 87. Most other places I get 89, 91, or 93

 

[ShadowsPapa]

But that old 3.8 is very sensitive to fuel quality. She just turned over 157k miles today. So I speak from vast experience with it.

Very possible - science supports that possibility. Especially with higher mileage.

 

[DieselInk]

My company used to own a chain of convenience stores. We had multiple different major brand stations and even some unbranded as well. ALL of our gas came out of the same fuel pipeline station where the 18 wheel tankers would fill up. Thus the gasoline starts as the SAME. HOWEVER with name brands: Texaco, Chevron, Shell etc, they each had a very specific additive mix that was added to each tank load. Those very expensive additives help with keeping the engine clean but normally not with mileage, which is directly related to the octane level.

As to the octane level, there were two different pipeline connection points for the trucks, one for REGULAR and one for PREMIUM. The tankers had multiple compartments and could haul both at the same time if desired. At the gas station they'd put Regular in one tank, and Premium in another tank. MID GRADE is a 50/50 mix of Regular and Premium. Some of the gas stations there was a third tank where they put in half and half. At some the Mid grade pump merely pulled 50/50 from each tank.

Keep in mind if the station that has large storage tanks which holds more than a single tanker volume (8000 gals) they might sneak a load of cheaper Regular in with the gas in a Premium tank and still sell it as Premium. Mid grade same thing, it was often not really 50/50.
If you're going to do a gas mileage comparison from brand to brand, just use REGULAR as they can't mess with it.


Interestingly the additives of the majors are VERY strictly enforced. We had small owners of single major brand gas station sometimes try to cheat and buy off brand loads of gasoline from other distributors every now and then and then pass it off a branded. The majors have "investigators" who obtain fuel samples out of the gas station tanks on a regular basis and have it tested for the additives. If the additives weren't in the gas they knew it was off brand gas and they'd fine them or even de-brand them.

NO STATION EVER INTENTIONALLY PUTS WATER IN THEIR GASOLINE TANKS. Gas and water don't mix. If water gets in a tank accidently it will pretty much stop dead the cars it was put into within a few miles if the water amount was very much. When that happens, the that car goes to the mechanic who tells the driver "water in the Gas" and then they go back to the gas station and yell SUE!! We did pay for repairs due to water in gas a couple of times.

 

[that_gladiator_kid16]

i fil up at speedway and i use 89 (mid tier). i feel like it gets better kick off the line and doesn't cost as much as 93

 

[NachoRuby]

I use 87 octane whatever is cheap. Manual Trans Rubi. 15-16 mpg inner city, 18.2 mpg overall, and 20-21 mpg on highway trips. My gas mileage has slowly crept up though. I was pretty disappointed at first. I think I'm settled in now at about 8500 miles. I haven't noticed any changes the last few fill ups.

100% stock, 285/70/17 MTs

I've put a few more miles on since this post, and fuel economy is still improving. I'm happy with it. I'm up to 18.8. that's respectable for a Rubicon on mud tires.

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