I guess at 37 mpg it's less of an issue, but does the MINI really need Premium gas? By my calculations, that makes it effectively 32 mpg if you were using regular gas (assuming $.20 difference between 87 and 91 octane).

If it needs it, why?

If it doesn't, why do they recommend it?

 

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Yes and no. The engine is design to run most effeciently off premium gas. You will get better performance but actually less mpg with premium. Regular gas gives better mpg but less performance and it is not as good for the engine in the long run. But if you are planning on selling your car after it gets 3 or 4 years old, you will save money at the cost of a little performance.

 

>>Just don't put leaded in it

Where does one even GET leaded gas these days? I haven't seen a "leaded" gas pump EVER.

 

Higher octane = higher efficiency = better gas mileage, not less. Also, even at 20 cents a gallon more, you're talking about $2 more each time you get gas. Big DEAL! Think about what your monthly lease or finance payment is: $350, $450, $500 or more! What's $2 once or twice a week!

Also the MINI was DESIGNED to run on 91-98 octane so you will get both better performance, mileage and engine life with premium gas.

 

I think, with a compression ratio of almost 11:1, that premium is indicated. I think you'd have pinging problems without it. Give it a try and let us know.

 

My father worked as a research chemist for Amoco for 28 years, and he said get the premium. Apparently if you feed premium gas to an engine that doesn't require it, you get very little if any performance boost, and in some cases less. On the other hand, if your car needs premium and you give it regular unleaded, you can see a drop in HP of 15-30%, depending on the engine.

Besides, the cost difference isn't that much. If you drive 15,000 miles a year and get 30 MPG, you're buying 500 gallons of gas a year. At $0.20 a gallon difference over regular, that's $100 a year. Not much for great performance.

 

Also check out How stuff works and find info re. compression and octane requirements.

 

When the manual calls for 91-98, it is referring to the European standard, Research Octane (RON). I'm not sure of the exact formula, but generally 91 RON is equaly to 87 US pump gas (R+M/2). The real question is whether or not your car "knocks" or detonates on fuel of a given octane.

>>My father worked as a research chemist for Amoco for 28 years, and he said get the premium. Apparently if you feed premium gas to an engine that doesn't require it, you get very little if any performance boost, and in some cases less.
Correct

" Higher octane = higher efficiency = better gas mileage"
very likely the case with the Mini, but not a generally correct statement.

Use the fuel that the engine was designed for. Typically in a high compression ratio engine, premium is required. If you don't use the higher octane fuel the ECU should sense "knock" (pre-ignition) and retard timing. A few downsides to this: 1) your engine has to knock a few times which is very hard on cylinder heads; 2) when the ECU retards timing your engine produces less power and loses efficiency; and 3) What if the ECU hiccups and you melt a piston? Not likely, but a very expensive possibility if it happens after your warranty is up!

Howstuffworks is a great site, here are a couple other links that go into more detail:
http://www.type2.com/bartnik/octane.htm
http://chemistry.about.com/library/weekly/aa070401a.htm
http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

Happy motoring :smile:

 

>>When the manual calls for 91-98, it is referring to the European standard, Research Octane (RON). I'm not sure of the exact formula, but generally 91 RON is equaly to 87 US pump gas (R+M/2). The real question is whether or not your car "knocks" or detonates on fuel of a given octane.
Use the fuel that the engine was designed for. Typically in a high compression ratio engine, premium is required. If you don't use the higher octane fuel the ECU should sense "knock" (pre-ignition) and retard timing. A few downsides to this: 1) your engine has to knock a few times which is very hard on cylinder heads; 2) when the ECU retards timing your engine produces less power and loses efficiency; and 3) What if the ECU hiccups and you melt a piston? Not likely, but a very expensive possibility if it happens after your warranty is up!

>>Happy motoring :smile:
So where does this leave us low compression S owners???

 

"So where does this leave us low compression S owners??? "
The reason you have low compression heads is to accomodate the boost. I'm not sure what the specs are for the mini engine, but let me throw out some hypotheticals: 8.0: 1 compression ratio on a forced induction engine, 14.1 psi maximum boost. Since atmospheric pressure is ~14.1 psi, the blower is effectively doubling atmospheric pressure (2 bar) creating an effective compression ratio of 16.0: 1. This is one major reason that "bolt-on" turbo kits are either tuned to very low boost levels or engine internals are changed or the engine goes *poof*

 

The US grade of 87 or better corresponds well to the Higher European standard numbers. In most cases 87 octane fuel is fine. The key is detonation. If you aren't detonating then you don't need higher octane. Try the lower octane and see how it performs. No need to throw money into the oil companies pockets if its not necessary.

BTW, higher octane fuel is formulated to higher effective octane with additives. Its cheaper and easier to produce than actually refining the fuel to a higher octane levels. Aviation fuel is refined to 100+ octane and its twice the price of auto fuel. Also since the additives are not involved in the combustion process, but still take up volume, higher octane auto fuel produces less energy than lower octane fuel without these additives.

Your choice. I burn the lower octane.


>>I guess at 37 mpg it's less of an issue, but does the MINI really need Premium gas? By my calculations, that makes it effectively 32 mpg if you were using regular gas (assuming $.20 difference between 87 and 91 octane).
>>
>>If it needs it, why?
>>
>>If it doesn't, why do they recommend it?

 

The bottom line is that BOTH of the MINI's are cars that require premium gas: due to their compression ratios (and boost pressures). If you use a lower grade fuel, the knock sensors on the cars will instantly "detune" the engines, and you'll have paid all of that MINI-engine money for nothing (as you'll be dramatically reducing the performance of the car). Worst case; the knock sensor fails, or can't adequately compensate and you have detonation (ie, hole thru the piston). NOT a good idea.

If you choose to use a lower grade gasoline, "pray" that you don't have an engine failure.... no warranty!

Most of us on this site use the best oil, wax, tires, etc on our cars; because they're special. Don't risk your engine for the cost of a Latte a week

 

Well said David, a trip to Starbucks is costing me $9 every time we go, so think about your car, and take good care of it....I will definitely be using premium, and if money is an issue then fill up when they have the sales days......

 

Like I said, Its up to you. I'll take the extra Latte thank you, and drive my perfectly tuned, non-detonating cars as well. I also own a Mercedes SUV that has a lower compression engine that supposedly needs high octane. The service manager told me that the reason they can't recommend lowert octane in the US is because the smog tests are passed using the higher octane, which does burn slightly cleaner. BTW, all European cars come with high octane recommendations because of the environmental regulations they must pass in some European countries and becuase in the difference in calculation of the octane value. but again its up to you. Personally, I matters not to me.

If you think burning lower octane fuel is a problem, then your going to love what happens to your car on the ethanol that is being added to fuel for emissions reasons.

Good Luck.

 

Well if premium burns cleaner that is reason enough....

 

Page #8 "For your own Safety" section, in the MINI Owner's Manual, states the following on the subject of fuel quality:

"Use unleaded gasoline only. Fuels containing up to and including 10% Ethanol or other oxygenates with up to 2.8% oxygen by weight (i.e. 15% MTBE or 3% methanol plus an equivalent amount of co-solvent) will not void applicable warranties with respect to defects in materials or workmanship.

Field experience has indicated significant differences in fuel quality (volatility, composition, additives, others) among gasolines offered for sale in the United States and Canada. The use of poor quality fuels may result in driveability, starting and starting problems especially under certain environmental conditions, such as high ambient temperature and high altitude.

Should you encounter driveability problems which you suspect could be related to the fuel you are using, we recommend that you respond by switching to a recognized high quality brand.

Failure to comply with these recommendations may result in unscheduled maintenance.

Obey pertinent safety rules when you are handling gasoline."


So it appears to be that the MINI's engine is pretty sensitive to different gasoline qualities. My dealer recommends using Mobil, Chevron and Amoco premium gasolines.

I primarily use Mobil and Chevron only. What does everyone else is using and why?

 

Chevron only. I wonder though. I use it for the Techron but wonder if stations are buying from independent distributors, is "Chevron" being sold without Techron??

 

2MINIS:

My dealer, Lauderdale MINI, recommends Mobil gasolines. In fact they say that BMW/MINI recommends Florida owners to use Mobil because they have their own distributors and generally have very strict gasoline handling and quality control standards from refinery to station pump. I didn't know this.

In order of preference, they issues the following gasoline brand recommendation:

1) Mobil (I guess Exxon falls in this category as it is owned by Mobil, but my near by Exxon station appears to be selling gas of dubious quality as I don't think they properly maintain their underground storage tanks (Water filtration).
2) Chevron (Never had problems with them before)
3) Amoco

They told me to stay away from Shell (Usually very expensive), Texaco, Citgo, Marathon and other less known brands.

I guess I'll stick to either Mobil or Chevron for the time being. Am I being too picky?

 

Recently in some conversations with some friends that are car experts, a few have recommended Mobil highly. One friend even said it is the best gas out there. There is a Mobil by my home, so I end of going there most of the time, originally out of convenience.

 

OK, So from Chemistry 101, we know that octane slows the progression of the flame front as it spreads thru the combustion chamber - slower burning means less chance of uncontrolled burn, i.e. no detonation. maybe that means cooler burning too!
Some of you kids probably don't remember the Shell commercials from the sixties that showed Enzo stepping out of one of His cars - every one left the Factory with Shell in it's tank - Good Enough For Me! (I use Chevron too anyway )

 

How about Sunoco, or Noco, two NE refinery brands? Mobil is VERY expensive in my area, and we don't have Chevron or Amoco...

Rocketboy_X

 

We don't have Sunoco or Noco here, so I am unfamiliar with their fuel quality.

A good bet would be to ask your dealer's service advisor for recommendations on gasoline brands for your MINI.

 

Hi again,

I see the question still rages. I really don't believe there is much difference between brands. Some additves are different. Techron, for instance, is merely the marketing trade name that Chevron uses to market their combination of cleaning and octane inproving additives that all refineries add to fuel. Wherever you are all the fuel available in any given area comes from the same refineries. This may be a single refinery depending on the area. Those refineries are owned by companies like Tosco, ARCO, and AMOCO. Chevron, etc sell them oil and pay them for the refining. This is to satisfy anti-trust requirements in some states. Independents buy the fuel directly from the refineries, so its the same fuel. Its the quality of the refinery that determines the quality of the fuel. Most refineries are run to strict standards.

If it is really of great concern, then do what the dealer does. All new cars come with some gas, and demo units are fueled multiple times before they are sold. Some dealers have their own pumps. Where do they get the gas for their pump from? If they don't have a pump, I'll bet they get it from the closest station to the dealership regardless of the brand.

In California, we have a bigger problem, ethanol. Ethanol has been demonstrated to seriously deteriorate fuel systems. It eats gaskets and seals. Try putting a rubber O-ring in a glass of vodka and see how long it lasts. A few years ago the California State government ordered refineries to use MTBF as an oxygenating additive to improve emissions. It did improve them. However, it turns out to be soluable in water so quess what; yes, it started showing up in the water supply. In a knee jerk reaction they changed the requirement to 10% ethanol. Right now its only in California, but look for it soon in other locales as the Midwest corn lobby twists arms to make a new market for their product.


Bottom line, do what makes you most comfortable.

Yes, I am connected to the oil industry.

 

>>Hi again,
>>
>>I see the question still rages. I really don't believe there is much difference between brands. Some additves are different. Techron, for instance, is merely the marketing trade name that Chevron uses to market their combination of cleaning and octane inproving additives that all refineries add to fuel. Wherever you are all the fuel available in any given area comes from the same refineries. This may be a single refinery depending on the area. Those refineries are owned by companies like Tosco, ARCO, and AMOCO. Chevron, etc sell them oil and pay them for the refining. This is to satisfy anti-trust requirements in some states. Independents buy the fuel directly from the refineries, so its the same fuel. Its the quality of the refinery that determines the quality of the fuel. Most refineries are run to strict standards.
>>Yes, I am connected to the oil industry.
So. Techron is not just a detergent? It is an octane additive as well? I thought it was just napthalene(?sp) related to common cleaning solution. And, if it is an octane additive, how much?
Thanks.