I don't think anyone had actually read up on my link.

Fuel really is a neat stuff.

The octane rating is a measure of the resistance of petrol to engine knocking. Engine knocking can damage the engine quite quickly. Some vehicles require a high octane fuel, and many vehicles less than 10 years old can run on lower octane rating fuel safely, but get better economy and power from higher octane fuel.
The octane number of a fuel is measured in a test engine, and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane which would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel. For example, petrol with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90.[1] This does not mean that the petrol contains just iso-octane and heptane in these proportions, but that it has the same detonation resistance properties. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers higher than 100.
Octane rating does not relate to the energy content of the fuel (see heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where octane is raised by blending in ethanol, energy content per volume is reduced.
It is possible for a fuel to have a Research Octane Number (RON) greater than 100, because iso-octane is not the most knock-resistant substance available. Racing fuels, avgas, liquefied petroleum gas (LPG), and alcohol fuels such as methanol or ethanol may have octane ratings of 110 or significantly higher – ethanol's RON is 129 (116 MON, 122 AKI).[citation needed] Typical "octane booster" gasoline additives include MTBE, ETBE, isooctane and toluene. Lead in the form of tetra-ethyl lead was once a common additive, but since the 1970s, its use in most of the industrialised world has been restricted, and its use is currently limited mostly to aviation gasoline.

Higher octane ratings correlate to higher activation energies. Activation energy is the amount of energy necessary to start a chemical reaction. Since higher octane fuels have higher activation energies, it is less likely that a given compression will cause autoignition.
It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, an uncontrolled ignition is not desired in a spark ignition engine.
A fuel with a higher octane rating can be run at a higher compression ratio without causing detonation. Compression is directly related to power and to thermodynamic efficiency (see engine tuning), so engines that require higher octane usually deliver more motive power and do more work for a given BTU or calorie of fuel. Engine power is a function of the fuel, as well as the engine design, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.
Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.
However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate, that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor – a small piezoelectric microphone which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.
Most fuel stations have two storage tanks (even those offering 3 or 4 octane levels), and you are given a mixture of the higher and lower octane fuel. Purchasing premium simply means more fuel from the higher octane tank; the detergents in the fuel are often the same.

 

More than once have I contemplated buying and old car just so I can run Avgas in it. The BEST smelling exhaust ever.

 

There is no need to wait until the service engine light comes on to get your first service. When you own the car for one year you need to call your dealer for a service appointment. They will change the oil & Filter and check everything that needs to be serviced.

After the first service you need to call them when the service engine light comes on unless you do not drive over 6 or 7 thousand miles. Then call them the second year. It is never to go over one year between oil/filter changes.

I changed mine at 2,915 miles "Speed-o-meter reading" (Not the Filter)

Dealer changed oil & filter at one year =(8,079 miles)"Speed-o-reading"

Dealer change oil & filter plus flushed & replaced brake fluid as well as all of the other filters at 14,345 miles. (Service engine light came on) Which was 6,266 miles since the last service.

I'm about to change the oil again myself because I just hit 18,000 miles.

Both times I went in for the service they replaced my wiper blades.

Changing the oil on a Mini is so easy a Caveman can do it. Changing the oil filter is not really to bad but I just let the dealer change it at the regular service. I believe changing the oil every 4 or 5,000 miles the filter don't need to be replaced. It would if you wait 10,000 to 15,000 miles.I think changing every 5 to 7 thousand miles using genuine Mini oil is the best way to keep out the sludge. Change the filter every other time and you will find that the filter is still good and not being bypassed.

I just went on my vacation and did 2,108.5 miles total. I ran at 75/80 mph for at least 1,900 of those miles and did not use a single drop of oil. A lot of traffic jams in Washington and Baltimore that caused stop & go crawling. I took a quart of Mini oil with me and did not have to open it at all.

I think the dealers that say gas causes the sludge are smoking OPIUM or just plain stupid and not facing a customers problem. If it is not because of using the wrong oil it has to be something wrong in the engine. If there is a problem they need to fix it. Remember the TOYOTA scandle.

 

Thanks for the great responses. This thread has been more informative than I could have imagined. And no one's called anyone an idiot. I think I'm gonna like it here.

 

I'm tired of arguing this point with people. Run 87 if you are that cheap. it's your engine and your repair bill.

 

Saving $1.25 each fill up ain't worth it.

 

 

I am sticking with what the owners manual says (and the input from fellow MINI owners). I am going to have to use 93 tho, I don't see many stations where I live that have the 91 octane. No big deal tho, I can mix it a little bit with the 89 to get around 91. Probably just stick with 93 unless I am super short on cash and need to save a couple of pennies on a fill up once in a blue moon. I'll never even think about putting 87 in it tho. But that is me.

 

MINIUSA speaks:

"MINI Division requires the use of premium fuel (91 AKI) only if you want to duplicate the official EPA certified emissions and fuel economy. However, if you choose to use less than 91 AKI (it is not recommended to use below 87 AKI), it will not harm the engine. It is important to note that there will be a reduction in fuel economy and performance and emissions will increase."

(Note that this answer is specific to my normally aspirated 2010 Cooper.)

 

Reading this thread almost makes me wish I lived in the U.S. of A. Almost!!

Here in Canada, we generally pay more for everything - including gasoline. I did some quick and dirty calculations...

Today in my neighbourhood, gas costs $1.07 per liter of regular, 87 octane gas. Converted to your American gallons, that's about $4.07 per gallon.

Premium 91 octane costs around 15 cents per liter more, in the $1.20 range per liter. That's $4.56 per gallon (or more.)

So, a 13 gallon fill up of 91 premium costs $59.28. Same fill up with 87 regular: $52.91. So, that's $6.37 difference - per fill up. Significantly more than the $1.25 per fill up difference that others from the U.S.A. have mentioned.

And - that's for gas with 10% ethanol added. I can't find straight, un-ethanolled gas anywhere near where I live.

I use regular 87 in my Justacooper most of the time, with about one "premium" 91 or 93 octane fill up every fourth or fifth tank full as a "treat" for my MINI. If the 91 were cheaper, I might use it all the time, but at around six-and-a-half bucks in savings for each fill of regular, maybe not.

All this discussion would be completely academic if there was any perceptible difference in the operation of my MINI on different fuels - - I would use 91 or better all the time if my MINI demanded it (or if I had a turbo). But the simple fact is, so far there is no reason to pay more. I can't tell what grade of fuel I have in the tank of my JustaCooper at any given time, based on the way the car operates. Regular (87) causes no discernible drop in mileage, power or smoothness of operation. So, I'll keep the $6.50 or so in my pocket after each fill up, thank you very much!

Just my two cents...

__________________________________________________ ___

 

33EJB, I believe Shell and Chevron are both Ethanol free.

 

We don't have Chevron here in Canada - - but I will check into Shell.

Thanks!!


__________________________________________________ ______

 

So in Canada 91 is about .50/gallon more, and here it's about .20 more. That's quite a premium, 12.5%. Here it's about 7.5%. But has is cheap here anyway. Back in 2008 when I paid $4.50 in CA I was like outraged. Then a year later it was down to $2.35 or something. I don't get the impression that Orangecrush thinks that 91 will hurt anything, he just says his motorcycle ran better and got more miles on 87 than 91. I spend about $2.60 more for a tank of 91. Cheap.

 

" In the United States alone, more than 70 percent of the gasoline Chevron sells contains ethanol." -- Chevron.com

 

I started out running 87 in my Justa. It had a small stumble/hesitation off idle on occaison. I switched to 93 octane and it went away.

In cars that have knock sensors and can dynamically adjust ignition timing.... higher octane gas will allow the most advanced timing. Advanced timing produces better fuel economy. (and higher NOx emissions.)

It's a trade-off, though. The fuel costs 10% more, but the advanced timing allowed by the more expensive fuel doesn't (generally) yield 10% better fuel economy. With 93 octane fuel, there's probably alot more "headroom" to advance the timing without getting knock. However, you'd probably start to exceed emissions. A good chip tune could probably eek out a little more MPG by advancing timing... at the expense of emissions.

 

Mini says you will get higher emissions with 87. See post #59.

 

And when the American dollar used to be up, that would have only cost us 22 bucks to fill up....

Seriously, when I moved to the US (from Alberta) I moved to Buffalo. The American dollar was worth 1.20-1.25.

Gas was not only cheaper in Canada at the time, they use Imperial gallons.

While most people were paying 25 bucks to fill up their tank in the US, we'd drive across the border to get chinese food and gas. I could fill up my tank, eat some good chinese food and still have 7 bucks in my pocket...

Ahhhhhh, the good old days.


Mark

 

That's my two-cents also. It seems, despite people's perception to the contrary, there is no definitive answer to the question of octane. The closest thing we have to one is Mini's statement that running as low as 87 will not harm the motor, but will/may have other negative affects. (See post 59 )

FWIW, my own experience is that i can tell when I've got 87 in the tank, but cannot perceive the difference between 89 and higher octanes. (Base cooper). And no, I'm not a throttle masher. I drive pretty sedately.

I track my mileage pretty closely and there's no difference there either (between 89 and higher grades)



Unfortunately, I can't find any Ethanol-free gas in Massachusetts. Even at Shell and Chevron.

 

The message from post #59 seems to me to be the definitive answer to the OP. Mini appears to say that the requirement for higher octane than the car actually needs, or will run on, is based more on EPA requirements than any inherent performance or durablity issues. Armed wih this information, everyone should be able to make their own choice based on the specific octane reccomendation for their car based on their owners manual.
Personally, I purchase gas at Costco which has only two grades: 92 or 87 and I can find no discernable difference between them in either MPG or performance other than $.25 per gallon, $3 per fill-up and $75 a year additional cost.

 

Its funny that this same discussion often appears on the BMW 3 series forums at Bimmerfest and Bimmerpost.
When you buy an expensive or semi expensive (Mini) performance car, most people would just use premium gas if its called for by the manufacturer.
Its funny to me. Here you just spent 35 to 55 thousand dollars (BMW 3) for a nice performance car or 25 to 40 thousand for a unique SMALL performance car (Mini) and you want to feed it cheap gas like its a Civic. Why didn't you just buy a Civic rather than a Mini Cooper (Justa) and have more room and better gas milage?

I have not seen anyone on this board discuss "Top Tier " gas. BMW, Mercedes GM and other manufacturers recommend we use top tier gas in our cars because it has better fuel additives that clean our fuel systems and the additives are in all grades of their gasoline. Top Tier gas is Shell, Phillips 66, Union 76 ,Texaco.

 

Top tier gas is marketing pure and simple. Any gas that says it is 87, 91, 92 or 93 octane will be just that. Nearly every gas has detergent additives in it, so it doesn't make any difference what brand of gas you put in your MINI.

Dave

 

Is that the same BMW that recommends we change our oil every 20,000 miles?


__________________________________________________ ________

 

FYI - - I'm quite sure Honda also recommends "top tier" for all models...

http://www.hondafitforum.com/showthread.php?t=297

I'm just sayin'...




__________________________________________________ _______

 

nvm.. I'm gonna stay out of it. use whatever you want.

 

To everyone who extends their oil changes to the crazy intervals that BMW sets, if you lease your car, follow those recommendations, if you own your car, regardless of synthetic, don't go that long. I owned a large repair shop for almost 10 years. I have synthetic in most of my cars and that oil gets changed every 3000 miles. If you see the sediment that builds up from the particulates that settle out of the oil, you would feel the same way. The oil can take it, the dirt it removes from the engine is what does the damage. Spend the money and change the oil more often. It's a little bit of money, but do you want to risk the reliability of the engine over time?