Using Premium Gas

[Chili]

Sorry, didn't read all of the replies, but... Running premium will do nothing for you unless your engine is designed to run premium, has been tuned to run premium, or has variable timing set to adjust to the fuel octane level.. All premium does is burn a bit 'slower' than lower octane fuel. That allows you to increase your timing without risking pre-detonation (usually referred to as pinging).

 

[Lucky j]

I have personnaly tried it in different cars and vehicules, and saw nothing that made it worth the cost difference of high octane vs regular gas.

And it was all rested in exactly the same condition. Gaz station, distance travel and weather. Was the same with people that told me their was a difference until I convinced them to make sure to make the comparaison in the same condition.

Even the motocycle test give me the same result. So to me, it is manufacturer recomendation.

But it's my opinion and what do I know.

 

[MOAK]

I don't want to get into the politics too much at all, as I said before, this isn't the forum for it, but your comment deserves a question/response.. If all you say is true, then why is it that the very conservative Bush administration gave away billions of dollars toward the research and development of ethanol production to ethanol producers? You sir, are certainly entitled to your own flawed opinions, but not your own facts. So called liberals, or greenies, have never been in favor of ethanol production, we have always known said production to be worse for the environment than good clean burning modern gasoline engines.. That's why the ethanol producers are soon going to loose their free ride .. Check your facts before laying blame, follow the money!!

 

[JPK]

I don't want to get into the politics too much at all, as I said before, this isn't the forum for it, but your comment deserves a question/response.. If all you say is true, then why is it that the very conservative Bush administration gave away billions of dollars toward the research and development of ethanol production to ethanol producers? You sir, are certainly entitled to your own flawed opinions, but not your own facts. So called liberals, or greenies, have never been in favor of ethanol production, we have always known said production to be worse for the environment than good clean burning modern gasoline engines.. That's why the ethanol producers are soon going to loose their free ride .. Check your facts before laying blame, follow the money!!

Here, do some reading and tell me which side pushed ethanol. http://www.fuel-testers.com/ethanol_fuel_history.html Plenty more is available via Google search. See particularly the dates, 1992 and 1993. They would be Clinton years, and prior to the Repulican take over of Congress. The left side has only very recently discovered that ethanol isn't the panacea it was billed to be by - guess who, the left. Obama wants to end ethanol subsidies for two reasons, to hurt a couple of his oponents - farm and oil lobbies - and because they reduce the pump cost of fuel per gallon, if not the cost of fuel per mile, and Obama wants higher energy costs, it is a core element of his leftist/phony green energy policy (or was until gas prices spiked recently!)

The right leaning farm lobby isn't blameless, they got a taste of gov't subsidies they want to keep them.

As far as a Bush being conservative - the word doesn't apply to either GHW or GW, let alone "very conservative." The only modern day Presidents who could be called conservative would be Regan and probably JFK.

A true conservative, not a Republican or Blue Dog Democrat but an actual conservative, would always become ill at the thought of a gov't subsidy or in general at gov't medling.

Do your reading, the facts are as I wrote. If the hour wasn't so late I'd provide you with a list of left leaning organizations which drove the ethanol bandwagon debacle. But feel free to Google up your own list, it is LONG.

JPK

 

[DEnd]

Yes, running a "stock" motor at a higher octane rating is not really a great idea. Which is why I qualified my statement with mods like intake/exhaust/plugs/chip/etc. Also, IMO a motor well over 150k miles is no longer "stock" either and just the added bump from 87 to 89 (low to mid in my area) is enough of an improvement for me since the higher octane fuels also have some 'extras' in them (such as stabilizers and detergents, but that varies by station chain) that low-octane fuels don't get. Also, where you live in relation to sea-level will have a lot to play in that as well. I know in the winter (colder denser air) my Jeep loves the higher stuff (although I never did a focused experiment with 89 vs 93 in my Jeep) vs in the summer when it gets hot I don't see as much of a change. The Jeep 4.0 has such a beastly compression rating that it will run on the higher stuff better than some other engines like a 4cly honda motor or a v6 ford motor. Not so sure about running high-test stuff in a JK motor though... probably not a good idea.

As for "at the pump/in the tank" additives, the only stuff I put in my Jeep is Lucas Fuel Treatment or 'Dry Gas' (but that is only in the winter or when it is really really wet out).

Firstly, running a higher the minimum octane in an engine isn't a bad thing... about the only thing it really does is "waste" money...
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Secondly the Mods you listed help the engine run more efficiently and don't really affect the internal temperatures or pressures of an engine... Though they may result in a slightly lower temperature, which would decrease the needed octane rating of it's fuel. The winter air at it's likely worst would keep the octane requirement the same. What is more likely is that you could actually run a lower octane fuel, as the octane rating is based on a high temperature and pressure. Both of these work together almost equally to determine the required octane rating of the engine's fuel.
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Thirdly the Jeep 4.0L does not have a beastly compression ratio. It's Static compression ratio is only 8.8:1 which is about equilivelent to Honda and Ford engines of a similar era (late 80's early 90's). All of their actual or rather Dynamic compression ratios are lower by a good amount.
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As for the Lucas Fuel Treatment it is basically polyisobutylene (PIB), which is a common fuel additive and is found in a lof of fuels already. Also if water in your fuel tank is a concern for you the best thing you can do is always fill up, and don't visit a gas station with a tanker delivering fuel for 30 mins-1 hour after.
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The thing is that there is really no harm done (other than to your wallet) by running a higher octane rated fuel. But if you feel the need to do it I suggest you hook up a scan guage or laptop and see if the recommended (lower) octane rated fuel is causing the computer to retard the ignition timing off baseline. If not then the Engine is operating at it's designed efficiency. If the computer is retarding the timing then you may want to look into it some more as you may have carbon deposits or other engine problems.

 

[4lowdean]

I just go off of what I read and what I hear. If I am a little misinformed on some of the details, then so be it. I try to keep an open mind and learn as much as I can so I will take what has been said in this thread into consideration.

As for the specifics of the chemistry and the physics of what is going on in the engine, I have read enough about the benefits and savings associated with running mid-grade in older high-milage engines that tells me it is a good idea. This is stuff I have been reading for years and even came up in the current (April 2012) issue of Road and Track.

Anyway, as long as I keep seeing a 10-15% boost in fuel-econom in my Jeep by running mid-grade, which equates to a savings in my wallet, I will keep doing it. :smiley_drive:

 

[MoGas]

This site will direct you to the ethanol free places in an area.

This site will provide you with the tool to check the ethanol content of fuel.

 

[Arctic Cat]

Ok here is my two cents and is based on my experience. I normally run on 87 Octane, but this last year I did an expedition on my TJ crossing thru 9 western state and 3 Canadian provinces all the way to Alaska and back and did over 12,000 miles. Normally I buy my fuel at 87 octane, but in some states I found that the blend makes my engine knock and I struggle climbing thru mountain and even driving against the wind. I decided to use 92 octane at some places and this cure the problem and I got better gas mileage, need to watch out in some states such as Utah that have 85 octane fuel as their “regular fuel” , even their mid-range may be rated as 88 octane.

 

[TangoBlue]

Ok here is my two cents and is based on my experience. I normally run on 87 Octane, but this last year I did an expedition on my TJ crossing thru 9 western state and 3 Canadian provinces all the way to Alaska and back and did over 12,000 miles. Normally I buy my fuel at 87 octane, but in some states I found that the blend makes my engine knock and I struggle climbing thru mountain and even driving against the wind. I decided to use 92 octane at some places and this cure the problem and I got better gas mileage, need to watch out in some states such as Utah that have 85 octane fuel as their “regular fuel” , even their mid-range may be rated as 88 octane.

I see your 2 cents and raise you 2 more. I normally use 87 octane all the time without any problems the last 10 years I've had my truck. However, same exact experience this last summer going from VA to Canada and the West coast, and back again. Gotta watch the octane numbers on the pump, not so much the cost per gallon, or you will pay the price of low performance.

 

[DEnd]

As for the specifics of the chemistry and the physics of what is going on in the engine, I have read enough about the benefits and savings associated with running mid-grade in older high-milage engines that tells me it is a good idea. This is stuff I have been reading for years and even came up in the current (April 2012) issue of Road and Track.

Like I said it's not a bad idea, just that people may not be getting the benefits they think they are getting. The reasoning for high octane rated fuel in high-mileage engines is that they are more likely to have carbon deposits which increase the heat held in the engine, may decrease the ability of the engine to breathe, and may raise the compression ratio of the engine. Higher octane fuels offset those to a degree helping your engine work more efficiently, they may also have more detergents in them which may clean those deposits away or keep them from getting worse.

 

[reece146]

Just ran a tank of Shell 91 through my Jeep ('00 XJ, 5" lift, 265s, 4.56, ARB Bar) to test the ethanol hypothesis. I saw no difference.

 

[MoGas]

Just ran a tank of Shell 91 through my Jeep ('00 XJ, 5" lift, 265s, 4.56, ARB Bar) to test the ethanol hypothesis. I saw no difference.

Depending on where you are located, even the "Premium" grade may contain ethanol. You only know if you test it yourself.

 

[reece146]

Shell 91 is 100% dinojuice.

 

[JPK]

Shell 91 is 100% dinojuice.

Not in states that mandate 10% ethanol, like MD, or in cities that have had to adopt ethanol to meet federal demands re clean air.

JPK

 

[reece146]

Well, it is here so I can't speak to other jurisdictions.

Regardless, made no difference compared to regular 87 with ethanol.