Ok, so let's go to the mountains of data. Taking a look at the scoreboard:

The following state that premium fuel is required:

Porsche/Audi/VW
BMW/MINI
Daimler
FIAT/Ferrari
Jaguar/Land Rover
Just about any other major auto maker outside the US.
A MINI mechanic who owns a shop devoted to the little car
About 800,000 google hits.
Me

The following state it is not:

You

Your call, eb.
I wonder which I'll believe...

 

Looking at the 2007 MINI manual, I can't find anything that says 91 octane is required. It's "highly recommended", but the only *requirement* is that the fuel be at least 87 octane. The MINI's manual even specifically states that using fuel between 87 and 91 won't affect the engine life.

Now, looking at the manual for my 2006, it *does* state that 91 octane is required. I've run 87 and 89 through mine with no problems, but *only* on long interstate trips where I'll be using the entire tank before I get off the freeway again.

 

Here we go once again on this topic of octane. The engineers who designed the Mini engine suggest using premium fuel. I pay about $2.50 more per fill up for 91 octane and really don't have a problem with that.

It's your car. Run what you like in it. If it runs good on 87, good for you. If you don't have long term effects from lower octane, that's wonderful. Me, I'll spend the extra couple bucks a week and follow the engineers advice.

 

It is generally accepted that a comp ratio of > 9:1 cannot use 87. The direct injected engine in the R56 S is 11:1.

 

Judging from this, clearly, Nightsky is the smartest of us all.

 

This is what I see to be the issue. Once you get a ping, that's already something happening that you don't want to happen. Krieg, you yourself said that the detonation needs to occur before timing retardation takes place. Further detonation is prevented, but you can't escape the initial occurrence.

 

Thanks, Maub

The biggest problem with that, though, is that you hope further detonation/pre-combustion is prevented. However, you cannot be certain. You have retarded the timing, but you still can't change the compression ratio. So, you continue to have misfires/issues. The engine can only compensate so much.

I also really take issue with this cavalier attitude that these cars are just throw away items that you can treat like crap, and leave the results to be someone else's problem. But the fact is that most people on this board will keep their MINI a long, long time, and be very upset when it dies. They therefore want to take the best care of it they can, so that it's longevity is increased.

 

I also use premium fuel (except for the highway-droning experiment I mentioned earlier), but that 9:1 "rule of thumb" leaves a lot out. First, the 11:1 (10.5:1, actually) is the *static* compression ratio. The *dynamic* compression inside the combustion chamber while the engine's running is what actually determines the octane requirement, and things like variable valve timing, camshaft specifications, combustion chamber design, cooling, the amount of boost at any given instant and the direct injection system all play a part in the octane requirement. Even the material choice for the cylinder head can make a significant difference - it's long been known that all else being equal, aluminum heads allow for higher static and dynamic compression without detonation.

For the R56, the owner's manual specifically states that using fuel between 87 AKI and 91 AKI won't affect the longevity of the engine, so if an R56 owner wants to believe MINI, who am I to say otherwise?

 

I agree with all that you've said here, but the fact remains that the octane requirement is dictated by the high end of the dynamic spectrum. So, while you may not run at specs that require that octane rating at all times, the fact that you can at any given moment shift those requirements to where it is needed precludes you from being able to use lower octane reliably.

Further, it should be common sense that an engine with that much technology on board should be fed 91, if for no other reason than, as I said before, American/EPA regulated fuel is complete crap.

 

Page 5 of the 2007 Porsche Boxster and 911 owner's manual:

Fuel Quality

Your engine is designed to provide optimum performance and fuel economy using unleaded premium fuel with an octane rating of 98 RON (93 CLC or AKI).Porsche therefore recommends the use of these fuels in your vehicle. Porsche also recognizes that these fuels may not always be available. Be assured that your vehicle will operate properly on unleaded premium fuels with octane numbers of at least 95 RON (90 CLC or AKI), since the engine’s “Electronic Octane™knock control” will adapt the ignition timing, if necessary.

DOH! Don't believe your manual Porsche drivers! Everyone knows your engine designers REALLY intended for your motor to self destruct on low octane fuel... just to sell more Porsches

 

Again with the jibbersh...

 

It's a chicken and egg, software/hardware, kind of thing. I had a 94 vw golf that would run better on premium. I think the Euro car makers don't really make a 'world' car. They slap on the detonator detector and call it 'world'. That golf was a stripper, btw. The Japanese lean more in this direction, in my opinion. My 07 Mazda 3 runs on the regular the mfr. specifies just fine.

I will say I just got 45.4 mpg on my last tank. It was CITGO premium. Isn't that Hugo (Chavez)'s company? It was only 20 cents more per gal than regular. I've put one tank of regular in my tank so far, and it did seem less peppy, but got about the same mileage as usual (~42 mpg).

 

Just for reference heres a good bookmark with the tech specs for the R56 engines.http://www.psa-peugeot-citroen.com/d...1103281940.pdf

 

In quotations below is the direct verbage from the '07 Owner's manual for MINI Cooper, MINI Cooper S, and MINI Clubman:

"Super Premium gasoline / AKI 91
This gasoline is highly recommended.

However, you may also use gasoline with less AKI. The minimum AKI Rating is 87.

If you use gasoline with this minimum AKI Rating, the engine may produce knocking sounds when starting at high outside temperatures. This has no effect on the engine life.

Do not use any gasoline below the specified minimum fuel grade. Otherwise the engine could be damaged."

Detonation (aka pinging) is very dependant on weather conditions and driving style. Long story short, if you experience a fair amount of audible pinging during your routine driving, you should contemplate a higher octane fuel until the pinging has subsided.

If you are using 87 octane fuel and not hearing any audible pinging, you are safe.

Having said that, if I owned an MCS and did a fair amount of 'wide open throttle' accelerating, I would pony up for the 91 octane:

Higher octane fuel = more advanced ignition timing during WOT = more horsepower.

When our non-S arrives in three weeks, I'll try a few tankfuls of each, and determine what octane rating is required for our car under our driving styles.

 

That's a good point, and I've actually seen high-performance custom-built turbo/supercharged cars that got around the issue by having two separate fuel cells and fuel pumps, feeding into a boost-operated switch right at the carburetor inlet or fuel-injection common rail. The idea is that for the vast majority of the time, the engine will be operating under vacuum or at most 2-3 pounds of boost, so the switch feeds the engine with the low-octane gas. Then, when the boost increases above a few pounds or the throttle's floored, the system switches over to the 100/110-octane gas before the engine gets to crazy boost levels and needs the ultra-high octane. That way, you're only burning the expensive stuff when you need it.

Of course, with 93 AKI only being about 20 cents more per gallon than 87 AKI, such a system would be overkill for the MINI, but I thought it was an ingenious solution nonetheless.

 

Oh my! Yet another contradiction to the absolutes stated by penguin.

 

Clearly, Krieg, you're the authority. We all bow to your knowledge...especially pertaining to the formatting of text on the interwebs. Once you figure that out, maybe you can move on to more advanced topics, like octane. This will help you educate yourself:

http://en.wikipedia.org/wiki/Octane_rating


EDIT: I see that you finally figured it out! Good for you! All that to basically say "Use premium. If it's not available, you can limp to premium in your Porsche, but use premium."

Face it man, you're not the genius you thought you were. It happens to the best of us.

 

Nice link Oxy!

 

That would be my link. See post #18.

 

That's not your link, you conceited a$$h0le...pay attention.

 

Cheese whiz...you two are both need to stop beating on each other please..

Go out wax your MINI's or something...

This looks to be very simple.

R50/52/53 Manuals state to use Premium Fuel. Yeah it will run on lower grades, yeah it may have reduced performance. It all depends on your state of tune and driving style. OEM with no mods and drive for economy, no jack rabbit starts, no pushing the limits and 87 will be fine. Do a few mods and you up the ante, then to be safe one should use premium fuel if only for the piece of mind.

For the R55/56 Crowd the manual states that Premium is NOT required. The R55/56 is not as high strung, therefore more forgiving when it comes to octane grade.

The bottom line...Use what you feel is best for you application and the way you drive. If you must have a pissing contest take it someplace else. PM each other to death for all I care, but stop beating each over the head.

 

Velvet was talking about Oxy's Peugeot link in post #38.

 

Name calling, profanity, insults. These speak volumes about your character and your inherent need to tear down others to boost your own ego.

I stated fact. You provided conjecture and opinion, and a list of "data" that could be refuted with a 2 minute download of two manuals in your list of "data".

Face it man. The best way to get out of a hole is... stop digging.

 

Oooops. Sorry.

 

Not in a hole. You began this diatribe by insulting me, and providing a resource with which to "educate" myself. So far, all you've listed is a bolded manual from a porsche that states just what I said...the manufacturer wants you to run premium. In the event you can't find premium at your Italian alps filling station, you can use something else until you get premium.

You continue to beat on this, but the bottom line is that these engines were built by people with PhD's to use premium. If and when you get a PhD in mech eng, chem and thermodynamics, I'll believe what you've got to say.