Premium Gas Myths

[scottagnew101]

My Grandfather printed this out for me and gave it to me. As i was reading, i could only think of my past 2 rovers and how they would act on cheap gas (none 90+ oct)

Car Talk

I kinda feel like writing these guys and giving them my input and telling them to test our rover engins. One line says "We dont believe that any modern engine that claims to require premium will be damaged by using regular unleaded judiciously*"

The key word being *Judiciously - Shrewd, sensible, wise or tactful.

Maybe what they mean by that quote is every 3rd fill up, filling up with regular. However, even 1 fill up with low grade makes my DII ping and just not play well. Any input? whats the deal with this article?

Scott

[tcpfl]

Tried the link but it comes back with this...

"Now, where did we put that file? We either moved it or removed it. In the meantime, can we offer you something else on the menu?"

[ArmyRover]

I use regular in my RRC and I used regular in my 740il bmw as well no issues

[atvsmurf]

I use whatever will keep an engine from detonating/pinging, anything more is a waste as far as octane goes...some of the brands, like sunoco, will have built in oxygenators and other secret additives, to increase the burn qualities and make a low test fuel act like a higher test...so you may want to look at the brands of fuel you use, not only the octane ratings, as the quality of fuel will vary from distributer to distributer...keep in mind that many stations with different names will be serviced from the same pumping truck...

[scottagnew101]

Car Talk

sorry about the link.

Thanks for the input on putting regular gas in your two non-domestic cars, as i tend to think they did this study on mostly american cars. My next fill up i guess ill try it one more time (1/2 a tank) with regular in the DII.

Scott

Thats also a good point. I mainly use shelle, what does everyone else use when they fill up? texaco with techron.... now i wonder if thats any good?

[cellulararrest]

Bottom line: Use the lowest octane that keeps your engine from pinging. That's all there is to it.

[Alak]

I use Shell 91 Octane V-Power.

If I were to use 87 or regular, I'd go with Esso all the way.


At least what we have around here. I've never run any low grade fuel in my DII. I always adhere to what the manufactuer' recommends.

Keep in mind, its also altitude, air tempurature and moisture make a difference.

[Administrator]

You want to run the lowest octane you can get away with, without causing detonation (pinging).

You'll get better gas mileage and more HP with the lowest octane possible.

Octane is simply a measurement of the temperature the fuel can resist before igniting, basically. So, having just enough octane to not pre-ignite gives you a more complete burn and results in extra power and fuel economy.

Having a higher octane would allow you to say, use higher timing and then gain extra power that way but stock ECU's are usually too conservative for this.

Being at a higher altitude lets you run lower then normal octane.. ie. if the manufacturer recommends "premium" -- that may be 93 at sea level, but at high altitude (3000+ ft. elevation) that means 91 octane. The air is less dense at altitude, and thus you can get away with lower octane without pinging.

Colder air results in more power for the same reason.. colder air is more dense.

Moral of the story... use the recommended fuel unless you really know your car/engine and the signs to look for/listen for as far as pinging goes... a bit of saved pennies/fuel does not replace an entire engine

[Disco Mike]

I believe these statements are way off base.
"You want to run the lowest octane you can get away with, without causing detonation (pinging).

You'll get better gas mileage and more HP with the lowest octane possible."

The lower octane you run in your Rover, the lower your power and mileage. Here in Colorado I run 91 octane at around the 6000 foot range and get around 18.5 MPG on the road at 65 MPH and around 13 MPG in town. I have had to buy 87 octane when up in the hills or when coming off a trail and my mileage has always dropped about 2 MPG. Even more important for us is the fact that Rover engine will carbon up on low octane gas and the repairs from the far out weigh any savings from buying cheap gas. Our engines can adjust to a lower octane, to a point but not to the build up of carbon.
Stay with the higher octane gas, enjoy more power and better mileage.
Mike

[scottagnew101]

mike, i was hoping you would chime in.

I read Wiki's Octane article Octane - Wikipedia, the free encyclopedia

its very interesting. The old DI blew an engine because of bad gas, thats what makes me do this when i read the myths about gas. The DI had clogged cats, and a cylinder that was not firing, then one more when out, then one of the bad cylinders threw a rod through the block which cracked it.

well put a new engine in it, my brother continued to run 87, and sure enough same problems as before... it seems like a simple step up in gas could have fixed a lot

Thanks for the input. Ill play around with (little 1/4 a tank fill-up's) of different gas and see. but i cannot complain about my premium

[scottagnew101]

Originally Posted by Administrator

... a bit of saved pennies/fuel does not replace an entire engine

couldn't agree with you more.

[DiscoAmigo]

Originally Posted by Disco Mike

The lower octane you run in your Rover, the lower your power and mileage. Here in Colorado I run 91 octane at around the 6000 foot range and get around 18.5 MPG on the road at 65 MPH and around 13 MPG in town. I have had to buy 87 octane when up in the hills or when coming off a trail and my mileage has always dropped about 2 MPG. Even more important for us is the fact that Rover engine will carbon up on low octane gas and the repairs from the far out weigh any savings from buying cheap gas. Our engines can adjust to a lower octane, to a point but not to the build up of carbon.
Stay with the higher octane gas, enjoy more power and better mileage.
Mike

Very good points! Thanks Mike

Adding my two cents, lower octane creates carbon build-up. Carbon build-up increases detonation problems by storing heat. So running low octane fuel for a lengthy period of time is a double-whammy for poor performance and mileage.

[Alak]

Point of fact, awhile back I purchased a 2005 Mazda Miata.

I used to run 87 octane in it for months, what the dealer recommended. Until I got to the back of the owners manual and it said recommended octane 91.

After trying out 91 octane a couple times, there was an obvious and noticable difference in performance. To counteract my thoughts of imagination, I had some friends try it unknowingly and they asked what I did to improve performance. It wasnt holy crap, but it was definately noticable.

Calgary's elevation is approximately 3,500feet above sea level.

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In my experience, you run what the manual says. If you feel comfortable with a lower rating, or higher rating, all the power to you. I've had turbo cars that recommended 87 octane and ran like crap on 91. I've seen some recommend 89. Keep in mind that the vehicles ECU is an ever adjusting, ever changing unit. It will compensate for altitude, air pressure. My Jeep recommended 87 for normal driving, and 89 for under load, towing or trail conditions.

[TaosBob101]

Colo & NM = 91 Octane. It's a few dollars a fill more for me, but I drive around 5280' to 10,000' all the time. And my commute is nothing.

I've got about 50k on a 01 Dicso SD, want to Seaform it (any carbon) before my big 60k service, so since I had it (33k) I run the Prem. ( It was a Florida lease, trailered out here.) I like my ride and cut my beer fund some to run Prem. When I have to. Runs good and I know I need plugs/wires/and a service tweak.

[atvsmurf]

buy what you like, all that I know is, the last engine I had tuned on a dyno saw no horse power or torque increase in power moving from a 112 to a 114 and even to a 116 octane, it needed the 112 cause it was a 402 bb chevy with ~11:1 compression running advanced timing...at 110 we had mild detonation, but once we ran the 112 there wasnt a trace...but we did have a crane cams setup that would throw a real good spark... the problem with the cylinder not firing sounds to me like an ignition problem...especially if the same thing happened soon after with the next engine and it was aminly isolated to a single piston....or he could be like my brother...blow any engine within a few weeks of drivin btw where is the carbon buildup a problem in these engines? I'm asking cause I haven't tore one apart...yet

bottom line is, if it makes you feel better, buy the higher octane, you might even want to buy some unleaded racing fuel(look for a sunoco station near a racetrack) I can't see it hurting anything....shoot I used to run racing fuel in my mustang just to get the smell of it but it ran the same 1/4 mile times with 87 octane or 112 whenever I would take it to the track...

oh and don't put a lot of faith in wiki...it is written by anyone who feels like starting an account then taking the time to edit the article...even if they know as little as us