Stop wasting money...run 87 in it from a reputable station and call it a day. You only need to run Premium gas in a performance vehicle that needs the extra octane.

 

Well, we have used both and premium works better. Mabye its because of the altitude of where we live. We liev quite high up.

 

Sure, all can take it..but most manufacturers don't recommend it...unless its a sports car where its designed for it.

89 isn't going to probably hurt it in the grand scheme of things, but it doesn't really help either..hence the waste of money.

Quite contrary..if you live in high altitude you don't need higher octane, you in fact can go lower. Most places in colorado don't even sell 91 octane...and instead sell 85 octane. I think "it works better" is a perception...I doubt you're seeing any real performance gain. It's all in your head.

But still, nobody's stopping you from using it - but you're mom is wasting her money, and I doubt you'll find many people who will tell you otherwise.

 

get your mom to buy 87 octane. and with the money she saves, ask her really nicely to go buy you a clue

 

I like to mix 'em all up at the tank and make a little octane cocktail... That really gets the engine going 'cause it never knows what's coming!

Seriously, FR-- use the 87! Jeep recommends it and it's cheaper. You can't go wrong, there.

 

You know, considering most of us have gone to more grades of school than you have lived years, telling us we are wrong about something factual is pretty childish. Just so you know.

 

i've said it before, and i'll say it again. i've never heard of a vehicle failing from following the instructions in the owners manual.

 

No, you are wrong. I have done dyno testing with motorcycles and if you don't have the compression for it, you will make LESS horsepower with higher octane fuel. I'm not going into it any further than this, but you are definately WRONG.

 

My thoughts on this subject:

1. The manual does say to use 87 octane (for those living at high altitude. you should be aware that you don't need as high an octane because of the reduced air pressure). The mfg makes their recommendation, and it's reasonable to assume that they thoroughly tested the vehicle with 87 octane. Let me emphasize that again: ****87**** octane.

2. Not all gas stations selling fuel correctly label the fuel. Some 87 octane is lower (there have been plenty of news report on this). Some mid-grade and premium tanks are filled with the same exact fuel as in the regular tanks (again, plenty of media reporting on this subject). Bottom line: While we assume that DMC used 87 octane for their testing, you have no assurance of what you're buying, no matter whether you buy it at a discount house, or at a "full service" station (again, plenty of media reporting on this).

3. Back in the 80s or so the car mfg's started putting knock sensors in their vehicles. These sense knocking and adjust (retard) the engine timing to eliminate the knock. Back in those days, every shade tree mechanic was aware that retarding timing was a quick way to reduce engine power, and to reduce gas mileage. But it was an easy way to run "cheap" gas without that annoying knock. However, we're not in the old days. Todays engines are a system with sensors and computers and on the fly adjustments that fine tune the vehicle for top performance at every moment of its operation. In my book, it's just magic. But, I'd be interested in a professional mechanic's/engineer's thoughts on what happens in the JK when less than 87 octane fuel is burned (since, bottom line is, we're all going to be doing it sometimes).

4. If you know for sure that you're buying 87 octane, I expect your vehicle will be fine. Of course, unless you work for the state inspector, you probably don't know what you're really buying--you just trust the station. If you experience knocking and you want to ensure that you have the best HP and gas mileage, try a higher grade fuel. It's your dime (difference in price). If it stops the knocking, great! Keep doing it. But, do be aware that the manual says light knocking won't harm the vehicle. Of course, the affect of knocking is more prevalent if the vehicle is under load: going up a steep hill or towing a trailer. What the mfg says "won't harm the vehicle" may be more than a little nuisance to you if you find that your JK howls in protest as you try to pass that Honda while climbing a steep mountain in Colorado.

 

fill up with a tank of 87 or 85 or whatever your regular is... and use the extra money to have it dyno-ed... run it almost dry, fill up premium and do the same. Post to jk-forum with the detail spread and either confirm or disprove your theory and everyone elses.

Thats the only way to either shut people up or shut up yourself. Definative proof!

Otherwise, its just senseless bickering about... "yes it does"... "no it dont"... "uh huh"

Personally i use 87... cause the book says so. And when the book said that it does not recommend premuim... i thought, " there is my excuse to never pay more for gas than i already do!"

good luck and get back to us on the test results!