buckbagger

In my experience running any higher grade fuel in a vehicle that does not require it, only caused problems with the computer making it run too lean or too rich making the engine throw a trouble code. I would go to jeeps web site or email them to find out what they recommended for a new wrangler. I cant believe that a new vehicle would not come with a owners manual, spend all that money and they make you print it off....

JCKustoms

X2!

I get the best mpg with chevron super! 40-50 miles more a tank compared to regular or plus!!!

thenag

my wife, before she was my wife, always ran mid grade in her 99 xj.

after convincing her to google search with phrases like "biggest waste of money on cars" and pulling out the owners manual (which actually indicates that running higher octane may hurt the engine)

She started running regular unleaded and actually her mpg went up a bit and had no noticeable change in performance. 3 years later the car still runs great.

google search for "waste of money car" you will come up with countless experts who will tell you to run what your owners manual says.

You only need higher than regular unleaded if you have a high compression motor, if you don't know what that is you don't have a high compression motor.

I have never looked into the "ethanol" thing so that may have some truth to it. In NM they only put ethanol in part of the year and on some vehicles there was a noticeable performance difference.

I have a 2000 f250 with a 5.4L that has run nothing but regular unleaded for all 215,000 miles of its life and it still passes emissions with flying colors so in my experience regular unleaded is just fine.

If you like spending the extra money and going against what the manufacture says go right ahead. It makes no difference to me.

Nathan
-99 xj swapped to regular unleaded in 07 and not going back (until its stroked)

Gorillaxj

this is not true. German market has high compression engine stock. which is why they need 91-93 (premium fuel) they don't tell you this or explain why when you buy a car.

Also Turbo/super charged vehicles need high octane fuel even though they have lower compression, the air is compressed and the octane needs to be high to ensure a good burn which will help to prevent pinging/detonation which can melt pistons/heads(in extreme circumstances).

Even newer Japanese vehicles will ping with anything below mid-grade (87-89) under load. fuel trims have become for precise and quick changing that the incorrect octane can cause problems given the correct situation, however most can correct for it as well.

I am not calling you out. In the situation of vehicles you are talking about you are correct. however i don't want someone to read this and think they can run regular in there audi, or regular in the turbo'ed car and have a serious and expensive problem. (which isn't GUARANTEED but very possible) I would just use what is in your manual. if you feel to step it up in octane it wont hurt.

From the Jeep Manual about fuel. not compete but what seams important based on your Question.


FUEL REQUIREMENTS
Your engine is designed to meet all emissions regulations and provide excellent fuel economy and performance when using high quality unleaded "regular" gasoline having an octane rating of 87. The routine use of premium gasoline is not recommended. Under normal conditions the use of premium fuel will not provide a benefit over high quality regular gasolines and in some circumstances may result in poorer performance.

Light spark knock at low engine speeds is not harmful to your engine. However, continued heavy spark knock at high speeds can cause damage and immediate service is required. Engine damage resulting from operation with a heavy spark knock may not be covered by the new vehicle warranty.

Poor quality gasoline can cause problems such as hard starting, stalling and hesitations. If you experience these symptoms, try another brand of gasoline before considering service for the vehicle.

Over 40 auto manufacturers world-wide have issued and endorsed consistent gasoline specifications (the Worldwide Fuel Charter, WWFC) to define fuel properties necessary to deliver enhanced emissions, performance and durability for your vehicle. We recommend the use of gasolines that meet the WWFC specifications if they are available.
GASOLINE/OXYGENATE BLENDS
Some fuel suppliers blend unleaded gasoline with oxygenates such as 10% ethanol, MTBE, and ETBE. Oxygenates are required in some areas of the country during the winter months to reduce carbon monoxide emissions. Fuels blended with these oxygenates may be used in your vehicle.
CAUTION: DO NOT use gasoline containing METHANOL. Gasoline containing methanol may damage critical fuel system components.
MATERIALS ADDED TO FUEL
All gasoline sold in the United States and Canada are required to contain effective detergent additives. Use of additional detergents or other additives is not needed under normal conditions.

98CherokeeLimit4x4

Break it in hard I promise you it will last longer

98CherokeeLimit4x4

The Rings seat alot better they tested it on A 1000 cars half Hard break in and half Easy. The Ones broken in hard had more power and lasted longer. Just dont over rev it