What grade of gasoline do use?

SavageUrge · **Posted:** Sat Dec 09, 2006 3:33 am

Tonight I decided to put some 89 octane gas in the Lib. Ever since the gas prices skyrocketed, my mileage has dropped considerably! I thought maybe upping the octane might help. So far, no real noticeable increase. So I started wondering to myself if you all run the recommended regular (87) grade since I've seen no one post here about their mileage dropping ever since the gas hike - I can't figure out why my Libby responded so negatively to it...So here I pose my question:

1300ZUK · **Posted:** Sat Dec 09, 2006 4:05 am

i did read somewhere where they did change the quality of gas to try and keep the cost down whether or not thats true i don't know. But run Regular all the time. I don't really trust the other varieties, you don't really need the higher octane, and i am not sure how long that 89 or 92 has been hanging around.

corwyyn · **Posted:** Sat Dec 09, 2006 4:17 am

Regular octane, whatever the rating is for the locale. Just changed my plugs a couple of days ago and have noticed some improvement; the ones I took out were the originals that I had cleaned and re-gapped about 15k ago. Higher octane is really only good for vehicles that are designed to use it, such as older vehicles (i.e. muscle cars) with high-compression engines. Using high octane gas in your KJ can actually decrease mileage...

Skyjump136 · **Joined:** Tue Jul 05, 2005 6:50 pm **Posts:** 1633

Regular (85 octane) :wink:

bmg9b · **Posted:** Sat Dec 09, 2006 10:47 am

So, is it bad to run the Plus grade? I have since I got my KJ like 6 months ago. My uncle (who is a MM on BMWs) told me that running the higher octane gas in new engines isn't going to help with mileage or power, but it will burn just a tad hotter which will help burn the crud that forms on the inside of the engine. Now, I'm no Nancy and I know how to change my own oil and other fluids, but I have no idea how the inner pieces of the engine work together. So, is he right or is that just a myth?

jason thompson · **Posted:** Sat Dec 09, 2006 11:02 am

SavageUrge wrote:

Tonight I decided to put some 89 octane gas in the Lib. Ever since the gas prices skyrocketed, my mileage has dropped considerably! I thought maybe upping the octane might help. So far, no real noticeable increase. So I started wondering to myself if you all run the recommended regular (87) grade since I've seen no one post here about their mileage dropping ever since the gas hike - I can't figure out why my Libby responded so negatively to it...So here I pose my question:

Our mpg went down right at 30K we did the full 30K & 36k mait at about 34K and the MPG went up
changing the plugs makes a difference but if you have the 7/70 I was told by a little birdy that puting in plugs that are not OE is cause for "question" should you have major engine problems

jason thompson · **Posted:** Sat Dec 09, 2006 11:06 am

bmg9b wrote:

So, is it bad to run the Plus grade? I have since I got my KJ like 6 months ago. My uncle (who is a MM on BMWs) told me that running the higher octane gas in new engines isn't going to help with mileage or power, but it will burn just a tad hotter which will help burn the crud that forms on the inside of the engine. Now, I'm no Nancy and I know how to change my own oil and other fluids, but I have no idea how the inner pieces of the engine work together. So, is he right or is that just a myth?

I dont know about the "burning of crud" but I do know that higher compression engines need to run the higher octane fuel

I also know that some of the ford engines made in the late 90's would have a real bad preignition problem causing it to knock and ping real bad under hard throtle run 92 and it does greatand gets better mpg

Elwenil · **Posted:** Sat Dec 09, 2006 11:39 am

89 Octane is the recommended fuel for the 3.7L in the KJ. Read your owner's manual, lol. It states that the Plus grade can be used for towing, I believe.

Jeepjeepster · **Posted:** Sat Dec 09, 2006 11:40 am

Ive always heard running a higher octane runs cooler? Thats that I run mid-grade when towing.

Cacher123 · **Posted:** Sat Dec 09, 2006 11:45 am

If ure vehicle doesn't knock on acceleration you don't need higher octane gas. All higher octane gas does is reduce the knocking. Read up on any of the racing forums about high octane gas.

jason thompson · **Posted:** Sat Dec 09, 2006 2:44 pm

Elwenil wrote:

89 Octane is the recommended fuel for the 3.7L in the KJ. Read your owner's manual, lol. It states that the Plus grade can be used for towing, I believe.

89 is middle of the road
87 is low grade and 92 is high
I have been running 87 in my TJ and KJ from day one and all is well

SavageUrge · **Posted:** Sat Dec 09, 2006 2:55 pm

Thanks for all the replies so far! I've been running the lowest grade gas I can find since the Libby was new since I discovered the cheapest gas ran the best and it seemed that the harder I drove it, the better my mileage would be - figure that one out! Until lately of course, as is the reason for this thread. I figured, I'd try to "burn some crud out" as bmg9b said, thinking maybe this was the reason my mileage was dropping. As soon as this tank is gone, it's back to regular to see if it made any difference. I don't think it will however, since I'm religious about using fuel system cleaner (Lucas Oil). I recently took a 100 mile drive going between 65 and 75 really getting on the gas hard and doing a lot of passing and hard accelerating the whole way and suddenly my mileage was back up to 19mpg, so I drove it hard on the next tank and the mileage dropped again!?!?!? WTF is going on? Now I baby it, (no higher than 60mph and I'm besting around 17.5 mpg. I can't figure out what my Jeep wants me to do! I only use two brands of gas, Hess and Kwik-Fill (A convenience store brand thats about the cheapest gas around). The Jeep runs equally well on both, so I know it's not the gas, since I've used only them since I bought it. I'm going to pull off that darn TBS pretty soon, and I just cleaned my K&N Intake, so I haven't the foggiest idea of what is causing this.

Cacher123 · **Posted:** Sat Dec 09, 2006 2:59 pm

I run a can of injector cleaner through about 2x a year or so. Seems to help and I guess it can't hurt. Also NEVER let your tank run all the way empty. It will suck up all the cr@ap in the bottom and screw up your injectors. Had it happen on my last Camaro. Had to have injectors replaced. Now I fill up as soon as possible after I hit reserve.

jason thompson · **Posted:** Sat Dec 09, 2006 3:02 pm

SavageUrge wrote:

Thanks for all the replies so far! I've been running the lowest grade gas I can find since the Libby was new since I discovered the cheapest gas ran the best and it seemed that the harder I drove it, the better my mileage would be - figure that one out! Until lately of course, as is the reason for this thread. I figured, I'd try to "burn some crud out" as bmg9b said, thinking maybe this was the reason my mileage was dropping. As soon as this tank is gone, it's back to regular to see if it made any difference. I don't think it will however, since I'm religious about using fuel system cleaner (Lucas Oil). I recently took a 100 mile drive going between 65 and 75 really getting on the gas hard and doing a lot of passing and hard accelerating the whole way and suddenly my mileage was back up to 19mpg, so I drove it hard on the next tank and the mileage dropped again!?!?!? WTF is going on? Now I baby it, (no higher than 60mph and I'm besting around 17.5 mpg. I can't figure out what my Jeep wants me to do! I only use two brands of gas, Hess and Kwik-Fill (A convenience store brand thats about the cheapest gas around). The Jeep runs equally well on both, so I know it's not the gas, since I've used only them since I bought it. I'm going to pull off that darn TBS pretty soon, and I just cleaned my K&N Intake, so I haven't the foggiest idea of what is causing this.

maby it wants tune up?

jason thompson · **Posted:** Sat Dec 09, 2006 3:05 pm

Cacher123 wrote:

I run a can of injector cleaner through about 2x a year or so. Seems to help and I guess it can't hurt. Also NEVER let your tank run all the way empty. It will suck up all the cr@ap in the bottom and screw up your injectors. Had it happen on my last Camaro. Had to have injectors replaced. Now I fill up as soon as possible after I hit reserve.

that is a myth told to women and girls so they do not run out of gas
if it were true then why do you have a fuel filter :?:

I run my work truck down to a gallon or less all the time and at 98K+ I have not even pluged the filter let alone messed up the injectors
the plastic tanks dont rust on the inside like the older metal tanks would so that helps too

SavageUrge · **Posted:** Sat Dec 09, 2006 3:19 pm

I just replaced the plugs, cleaned the air filter, cleaned the throttle body and checked the tires less than 250 miles ago, so unless I'm missing something, I don't think it's a tune-up it needs. Thank you, though!

1300ZUK · **Posted:** Sat Dec 09, 2006 3:26 pm

if it makes you guys feel any better, i just took out my original NGKs after 46K miles, and put new plugs in and my mileage dropped. I guess thats what i get for not wanting to Order NGK's

Jeepjeepster · **Posted:** Sat Dec 09, 2006 3:28 pm

Keeping gas in the tank helps to cool the pump.

bmg9b · **Posted:** Sat Dec 09, 2006 3:44 pm

Elwenil wrote:

89 Octane is the recommended fuel for the 3.7L in the KJ. Read your owner's manual, lol. It states that the Plus grade can be used for towing, I believe.

It also says you can use the middle grade... at least mine does.

Cacher123 · **Posted:** Sat Dec 09, 2006 3:59 pm

Quote:

that is a myth told to women and girls so they do not run out of gas
if it were true then why do you have a fuel filter

I dunno. I was there when my camaro tank was dropped and there was lots of stuff in the bottom. There was def some funny colored water as well as little flakes of metal. Granted the tank was metal and I really haven't had any familiarity w/plastic tanks like ours but it seems like a wise precaution. I would think that's there's gotta be at least a little water in there from contamination, condensation, cr@ppy gas once in a while, etc. No use sucking that stuff up into a touchy injector system. :cry:

What grade of gasoline do use?

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