98 octane fuel: Should I get a tune to run it?

J

JohnJ78

TJ Enthusiast
Joined
Dec 26, 2020
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125
Location
Australia
I know these are designed for 91 octane or whatever. I have 98 octane here and am tempted to run it.

Will I damage my engine running high octane fuel.... and is there en ecu tune I can get specifically to give me more power by running this fuel? Quicker off from the lights etc. More touque.
 
All you will do is waste your money. High octane gas has no more energy in it than regular gas. Some premium brands may have more additives in them but these just help your motor run cleaner. Higher octane prevents pre-ignition when compression is raised. High altitude regions, I believe above 5K feet, in the US use lower octane gas than the rest of the US. Unless you raise the compression of your motor there is no benefit.
Also I believe Australia uses a different formula to measure octane I know Europe does.
 
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JohnJ78 said:
I know these are designed for 91 octane or whatever. I have 98 octane here and am tempted to run it.

Will I damage my engine running high octane fuel.... and is there en ecu tune I can get specifically to give me more power by running this fuel? Quicker off from the lights etc. More touque.
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I don't know how the Aussie octane levels compare to the US levels but I can guarantee you will receive absolutely no benefit to running a higher octane than your owner's manual or the sticker next to your gas cap recommends. All additional octane does is make it harder for the engine compression alone to ignite the air/fuel mixture before the spark arrives. High compression engines, which the TJ is not, can prematurely ignite low octane fuels so for high compression engines, a higher octane is required. For your low-compression Jeep engine, a higher octane fuel would be wasted. Not to mention higher octane fuels are harder to ignite and slower to burn so the potential exists for deposits to be left behind if you run a higher octane than is required by the engine.

And at least in the US, high octane "premium" gasolines contain no more cleaning additives than standard gasolines do.
 
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All gas in the US is the same. It travels through the same pipelines. The only difference by brand is that when a truck is loaded at the tank farm the specific additive package for that specific brand is added to the tanker truck.
 
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The only reason I ever put slightly higher octane gas in a 4.0 was with my old XJ with 250,000 miles and a bad case of spark knock. I largely solved the problem by dripping some water into the intake to clear out the carbon buildups caused by a lifetime of driving like a grandma.
 
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John it might throw 02 sensor codes? I run a couple of tanks of 98 RON. didnt make any difference but changed back to 91 RON when I read its not good for the 4.0.
my wife's Hyundai gets occasional pre ignition rattle so I top up with some 98 and it cures it.
 
WASTE. OF. MONEY.

You do realize what your factory compression is right? And that your 4.0 has more in common with tractor than it does a Ferrari?
 
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I buy the Non-ethanol fuel for my Wrangler here. It is 91, but would gladly buy 87 non-ethanol if they had it. My rig gets almost 2 mpg better with the non-ethanol.

I do run the non-ethanol in all 3 of my rigs. Truck needs it, 10.5:1 and my CJ5 sits for months on end at times. It's 1$ more a gallon though...... 🥴
 
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