timlab1955

My CG 2005 calls for Regular ok, but mid grade perfered. It runs okay on both so I don't mind. This year we are driving from PA. down to SC and I'm wondering if I would hurt the engine if I put high test in it?

JeepFaced

Im sure there are going to be all types of different opinions in this thread.

I'm fairly certain you can use all of the non-diesel grades at the pump without issue, not to include racing fuels and kerosene if they have that.

The higher octane gas improves efficiency of combustion and reduces knock (non-combustion). There are only two true grades, low and high. Anything in between is simply a 50/50 mixture of a SERVICE STATION's High and Low octane fuels.

On a side note, I would recommend not using the Ethanol blends if you can get away from it. Not only is it NOT efficient for the vehicle and the economy, but the difference in the fuel actually reduces your MPG and increases wear on internal components of vehicles made prior to 2007(?).

I would recommend mid grade always, unless you have a delicate vehicle which you should use the high. And stay away from discount fuels such as Wal-Mart and Kroger. You would be surprised at the junk that comes out of your engine on a Seafoam binge after changing gas stations.

npk

i share your opinion on ethanol, but i have never heard the part on internal component wear. i was told the only damage that could occur was the degrading of rubber parts in the fuel system like the fuel line and o-rings. the newer cars have synthetic rubber that ethanol doesn't break down. 2 stroke engines can be damaged by ethanol. the ethanol can bond with water in the fuel and separate from the gas and oil. that can decrease lubrication when it enters the engine.

if i am incorrect about ethanol not damaging engine parts i would like to know the specifics.

Bustedback

No need to run premium fuel in your Jeep. It won't hurt anything to run it other than your wallet being a little lighter, but you'll gain nothing by running premium.

xj wheeler

With vehicles such as the grand cherokee overland with the h.o. 4.7l you get the extra power of the high output version only when running premium. Otherwise you would just get the normal 4.7l output, but no, it shouldn't harm anything to run regular.

Gee oh Dee

Well said.

MUDRUNNER AZ

I have a 98 5.9 which call for high octane. at the time i had a 60 mile commute one way and i tried the different levels from mid grade to high not much differance noted in power or mileage but on low grade it would ping and knock. i still run mid grade due to price these days and have had no issue.

JeepFaced

You said just what I meant. I hope it didnt look like I was insinuating it would eat away metal parts; I meant the rubber, plastics, etc. I wasn't sure on the year they started making the E85 vehicles with the upgraded PE and HDPE plastics but guessed at 2007. My first instinct said 2003. I truly dont know.

I worked at a (discount) gas station for a while and did extensive research where our oil was coming from (suppliers) and what types... and when we had been mandated to switch to ethanol blend, we had to clean out the holding tanks for a substantial cost to upgrade connections and seals and I talked to the installers because thats me. =)

Oh yeah, in the 2008 time period, you could look in the Financial section of the newspaper, and find the price per barrel of crude oil and roughly estimate the next day's gas-at-pump price. What I found that if you take the price of a barrel, lets say, today's price of 118.13 a barrel. Divide it by 33 (lowend) and 30 (High end) to get two figures -- 3.579/$gal and 3.937/$gal. That's the "Fair Trade" price range. Looks like it still works. (gas in my area is $3.59/g) Gas price at pump will vary according to the oil supplier and what additives or further refining they do. Typically, Shell is the most expensive. Discount suppliers give you a lower price at the pump, but pretty crappy gas that will in turn decrease your MPG and build up a lot of sludge.

KEEP IN MIND that every barrel we pull out of the ground or ocean floor means that we have to dig that much deeper. They are microwaving rocks in Canada to extract oil, and using caustic hydraulic fracturing to use chemicals to break down the geologic elements to exude oil, and pumping saltwater into deep holes to float that oil up to the surface where it is easier to get. There is more and more contamination and refining necessary. Use low or mid grade at a supplier that uses good additives and cleaner fuel.

Regular customers who were unaware of the changes (no notification that E-blend was being used ..I think it was E15 maybe?) had to come back to refuel more often and complained of more maintenance issues than usual. I noticed the increase in crappiness of my VW.

As for the Jeep, I am with the rest of the fellas above me. No need to get anything more than Mid grade.

Bustedback

That is the only reason there is premium grade, the higher octane keeps the engine from pinging because the the fuel is actually harder to light off than regular unleaded. You will not gain any horsepower by simply running premium unleaded fuel. The engines in our Jeeps are considered to low compression engine, 8:1 for the 4.0 and something like 9:1 in the v8s, engines with 10:1 and higher need the extra octane to keep from pinging.

As a side note: running a higher water to anti-freeze ratio will help with pinging because the higher water content will absorb heat faster than anti-freeze/coolant and keep the combustion chamber temps a little lower. A 70% water 30% anti-freeze/coolant mix will work just fine in most areas where there is no snow.

timlab1955

I thank everyone for their options in this, as this is my first jeep. I had forgotten to mentioned that the engine that I have is a the MDS 5.7 HEMI. My brother has a truck with either the same or higher engine in his, and on long trips he always puts the higher octane in it to (according to him) clean out the engine.

Bustedback

If paying for premium gives you the warm and fuzzies, go for it.

ct67_72

You hit my theorys nail on the head
I get better mileage in my 05 when running higher grade fuel. I assuem mostly due to what you have said. With the lower octane fuel the computer is pulling timing to resist detonation and losing a little bit of efficiency. This could, potentially mean that you would have better performance using higher grade also, but in the 3.7 I highly doubt anything noticeable, as its a little lacking to begin with.
I have always said that the only difference in fuel is its ability to resist detonation and would make no difference in an everyday engine.
Until I began to think to my self about tiing, and computer controls, I told my wife she was crazy when she claimed better mileage on higher grade fuel. But after thinking about it, it does make sense.

ct67_72

oh, to add, higher octane in its self will not improve economy, but the increase in timing because of its ability to resist detonation will.
Wanted to clarify that

stomper27

and also, adding a higher octane will not improve the Economy either.

It just goes into the pocket of Mr. Oil Tycoon.... can I get a amen my jeep brothers