any value in buying 93 octane over 91? i understand the 91 is required to keep knocking down in the higher compression mini engines. will 93 increase power at all- i suspect not..but thought i would query the experts....


TIA

 

I've never heard an authoritative answer on this question either. Is 91 octane pump gas high enough to prevent knocking under *all* circumstances, even heavy acceleration? Or is 91 just enough to prevent knocking under *most* circumstances?

I guess the best way to find out would be an OBD-II monitor that would let you monitor the voltage coming out of the knock sensor in real-time. Then, you could figure out the minimum octane required to keep the knock sensor from activating under heavy acceleration.

Scott

 

Your car will perform the same either way...it's tuned for 91 so just run that...if it's cheaper.

Here we don't even have 91. Some places have 92 but most have 93 as the only choice for "premium" gas.......87/89/93. So I run 93 all the time.

In my old car, an 03 Cobra, it was tuned from the factory as well to run on 91...since it's the lower octane "premium" gas out there. Since I run 93 I got a tune that bumped the timing to run on 93 and it gave me about 15RWHP actually. (Note this is on a car that had over 400rwhp to begin with).

 

I've got no doubts that 91 octane will keep the engine safe, and will probably keep the knock sensor from adjusting the timing under most conditions, but has anyone actually tested this and confirmed that 91 octane will keep the engine from knocking under *all* circumstances?

I wouldn't surprise me if MINI only listed 91 as the requirement to keep from scaring the people who live in places where 91 is as good as it gets. If the knock sensor is still activating occasionally with 91 octane gas, then there's probably a little more power to be had by running 93 octane, if it's available.

Also, don't forget that even if our engines *are* "tuned for 91", that goes out the window for the supercharged cars when you start swapping pullies to increase boost. That increases dynamic cylinder pressure and increases the octane requirements, and it's one of the most-common modifications we make to these cars.

Scott

 

officialy i have no idea but theres a difference between 89 and 93 so i suppose theres still a small difference between 91 and 93, its more that the cars feels heavier then anything else

 

Your car "feels" heavier with 93 octane in it????

Hmm, must be those additives they use to make it heavier

Read http://www.quiktrip.com/gasoline/myth.asp

Riqui wrote: Also, don't forget that even if our engines *are* "tuned for 91", that goes out the window for the supercharged cars when you start swapping pullies to increase boost.

I dont know if that is true or not true but if it were true, how do you explain that JCW cars still only require 91 octane?

 

Depends on where you live. The only difference is that the 93 can handle a higher compression before exploding. The exploding is what causes the knocking.

The reason some places ofer 93 and others 91 has something to do with humidity and oxygen. If you live in the high country you probably have 93 if you live on the west coast you probably have 91 available.

In the end I beleive that depending where you live 93 or 92 is equivalent to 91 at other locations where 93 would be more than you need.

 

Not exactly, here is Colorado, 91 is super (5000 - 10000 ft). When I lived in Northern California, 93 was super.

 

OK, maybe I had it backwards. There was a reason why some places offered 91 vs. 93 and I thought it had something to do with how the environment effected they way it burns.

 

The mini can utilize up to 98 octane in its computer.

the engine, if the computer was not involved can utilize over 100 octane easily.

the compression of a MC is 10.6:1 right? the MCS is less but the supercharger puts it back up to that or more. thats enormous compression for a modern car. that means it loves limitless octane (well, more than we can get normally at the very least)

under 98 octane, the computer retards timing to prevent damage to the engine, aka, knocking.

so, fill er up with max octane you can find. It will perform better for long stretches, up mountains, dragging around people in the car, etc. Supposedly not a huge difference. However, the engine enjoys it and also it is more efficient per mile. More power? yes but default it does have more power, usable power.

 

Because if MINI spec'd a higher octane requirement than 91 for the JCW cars, they'd be getting panicked calls from owners that can't find anything higher than 91 where they live. From a public-relations standpoint, it's better for them to continue to list 91 as the minimum, and just rely on the anti-knock sensor to keep the engine safe when under high boost (which is only a small fraction of the time).

Scott

 

i

 

i remember an article a while back regarding sunoco not making 94 anymore for cost reasons. i have a sunoco that sells 93 pretty reasonably priced, so i use it on occasion - i am in upstate new york.
there are a few places that only offer 87/89/93, but most stations include 91

lots of good answers.

 

So if optiumum octane for a MNI is 98 then would a bottle of octane booster from the local auto store do the job? i.e. increase the octane from 91-9?

 

What is your reference for this piece of information

If the car is not knocking, your wasting your money http://www.quiktrip.com/gasoline/myth.asp

If your car doesn't knock or ping on lower octane gasoline, paying for higher octane is a waste of your money.

 

That may be true for older cars but for the newer cars with knock sensors the computer reduces compression to compensate for the lower octane in return reducing performance and possibly fuel economy.

Although I would like to know the reference for the 98 rating being optimal for MINI as I would think that 91 or 93 would be the max necessary for full performance.

 

If you can't find higher octane gas at your local pump, couldn't you just pour in some of this?

http://www.goldeagle.com/104plus/products.htm

 

Even though running your car at a high performance level, I really doubt that everyone really needs to do it all the time. Unless your car is a track car, I believe that running premium or mid-grade should be fine.

medic

 

Here goes https://www.northamericanmotoring.co...t=octane+knock

Towards the end of the thread the statement is made. Also note how 100 octane is considered fine and great to use. midgrade???? never consider it. highest you can get with best quantity of additives possible

 

yea it lags, feels like its got six people in it

 

our engines are NOT tuned for 91. that is the minimal level octane you should use without suffering big consequences. They actually arent tuned at all. The timing is variable depending on knock, really, that negates the whole idea of tuning as you cant adjust the timing except for adjusting that variable control software. The engine at its 10.6:1 compression enjoys upwards of 100 octane. However, the software only can use ~95 octane or ~98 octane to its fullest. 95 or 98 I say as it seems there is a discrepency about how to calculate octane in terms american vs European measures. Some say the engineering comments are written in Euro terms, others, like me, believe that the engineers already know their audience and know the different methods of gas ratings in countries and therefore, they mean 98 american octane. Who knows though. Doesnt matter as octane only goes up to 93 in the USA unless you add Cam2 racing gas for 100 octane.

Timing adjusting means that it is compensating for crappy octane gas, not using it for its best.

 

Chow, I need to borrow your emoticon.

 

I know what you mean by 'feeling heavier'. When I go on a business trip with my laptop and store a lot of data... my laptop feels 10 pounds heavier on the return trip. Those zeros and ones really add up.

YD

 

Thanks. Tuls agrees with you ... appreciate the reference.

However note from your own reference FAQ

If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away.

Tuls seems to think 91 octane is NOT the optimum setting.

 

91 is proper MARKETING octane. to say a car needs 95+ octane to get full power would be marketing suicide. car company would love to say it can use 89 or 87, that sold many crap GM cars in the 1990's. however, what the engine wants is obscured from view.

t does enjoy 95 octane and can use it. The sicience of the engine just screams that must be so. the physical engine itself can use it, all the timing has to do is not retard and it will allow for full usage of a higher octane gas

every piece of your car's manual, every speck of the car itself, every option, every MA and every dealer advice is to get you and more people to buy it.