We are considering a purchase of a Mini Cooper and have one question: Why is it necessary to use Premium Fuel? One answer I got was that you'll get 'Better Performance'. What exactly does that mean? We aren't going to be racing this car.

If others use Regular gas, what happens?

Thanks,

Ron

 

The higher octane basically means it's less likely to ignite too early. It's not that it gives more power but think of it more like it allows for more power if the car is tuned for it. It allows for more pressure(especially important in engines that use turbo/superchargers) in the combustion chamber and more aggressive ignition timing. If you use lower octane in an engine tuned for higher octane fuel, it will compensate by backing off on the timing which will cause less power and likely less comlpete burn combined with less fuel efficiency. Also I wouldn't be surprised if using lower than recommended octane levels cause more carbon build up due to a less perfect burn.

It's not that the fuel is inferior, just that the engine wasn't designed around it.

 

High compression engine take high octane fuel Octane isn't energy, it is resistance to ignition. Regular will ignite early and will cause loss in mileage, performance and power. It might cause engine damage too.
Go for the Mini, the extra $4 you spend filling it up won't break you and the smile will do you some good.

 

Basically, you can expect to get about 2-3 fewer mpg on regular (that was my experience early on, which sealed the deal for me to stick with premium). As they say, YMMV. I get 33+ mpg with my '08 MCS. At current prices (premium is about $0.20 more than regular) anything better than 2.48 mpg improvement is a bonus. I figure it's about even, so I opt for what MINI recommends, since it really costs me nothing in the long run.

 

The earlier you can ignight the fuel (up to a point), the more usefull work you can extract from each power stroke in the engine. But also, the higher the cylinder pressures are. High cylinder pressures can create detonation, which is desctructive. So you don't want too much advance in your timing, or you get knock.

Now on to the Mini engines. They have something called knock sensors on them. These are basically microphones that listen to vibration in the engine block. With this invormation, the engine can adjust timing as needed to get as much timing advance as the ECU thinks should be there for optimal operation safely. But if it hears the onset of knock, it retards the timing. The engine does this on a cylinder by cylinder and power stroke by power stroke bases (it's actually kind of cool)!

So now to gasoline. The higher the octane, the more the gas resists detonation. This means it will allow for more advance. This means it can do more usefull work. This means not only will you get better acceleration, but you also will get more gas mileage. Really, it's a win win.

Now, how much mileage increase you get really depends on how you drive, and will vary owner to owner. here's an extreme example: I was leaving Laguna Seca, (really Mazda raceway Laguana Seca....), and needed some gas for the drive to AMVIV. I threw in 11 gallons of 97 octane (at a rediculous price, I may add) and with this mix in my modified car, I was getting almost 40 MPG at 85 MPH! (I think there's too much timing advance in my tune....) And this is with the first Generation supercharged Tritec.

So, what does this all mean? First, you don't really have to worry about engine damage with regular, as the knock sensor should keep you out of trouble. Second, that the appearant savings from the cheaper per gallon price of regular will be offset, to some degree, by the increased MPG that you get with premium, so the real savings is less than you think, and can actually dissapear all together to become a cost, depending on driving style!

Matt

 

Many people use regular in a MC and have no complaints. The engines in the MC and MCS were designed however for minimum 91 octane for best performance and gas mileage. I especially would want to use premium in the turbo and supercharged engines. As others have said, for only a few $$'s more per tank, you get better MPG's and power as well as not giving the dealer a reason (although remote) for denying a warranty claim for some related failure.

 

Let's use an analogy since the technical has been covered.

Higher octane keep the fuel/air mixture from pre-igniting. Pre-ignition is like pre-ejaculation, they're both VERY bad. If you go in and you're done, your girlfriend isn't going to be happy. If it continues she's going to leave... or kill you. Same with your motor, if you get pre-ignition too often your motor is going to kill you too. The only problem is, you can maybe get pre-ejaculation twice a day, your motor can get pre-ignition 7000 times per second. If you did that to your girlfriend she'd probably kill you in a few minutes too.

Wikipedia has a really goo technical article on Octane and what it means:
http://en.wikipedia.org/wiki/Octane_rating

 

I have a new 2010 MC Auto and ran three tanks of premium in it. Reading the manual it says you can use 87 octane fuel which is regular. While I agree that if I was running an S I would use premium but, so far, I can tell no difference. I may suffer a bit in MPG but, since there is no competition for premium I find a 25-30 cent per gallon difference. On a tank that would be about 10% at current prices. Time will tell but, it is not because you can't, just a matter of choice as someone else noted.

 

I find it incomprehensible that this topic still pops up. The car is designed to use premium fuel. It will perform as advertised and get good gas mileage. We're talking about 2-3 dollars per fill up for the premium fuel, what's the big deal?

I'm not trying to be rude. I understand that the media tells people not to pay extra for premium fuel, that it won't make much difference, and for the vast majority of people, that's true. Cars that are designed for use with 87 octane will not benefit from paying for premium, whereas cars that are designed for premium will pay some sort of penalty for not using it, weather it be losing performance or mpg or both.

Just buy the premium and know that your car is running right.

 

Quoting from the 2010 owners manual pp101: "Required Fuel - Super Premium gasoline/AKI 91 However, you may also use gasoline iwth less AKI. The minimum AKI Rating is:
Cooper S, John Cooper Works: 89
Cooper: 87"
As I said, I am using 87 and it works just fine, even the factory say it will.

 

I think the manual is simply stating that you can use a lower octane if it's all that available. Of course your car will function, just not as it's supposed to.

 

really, this isn't worth arguing about. The fact is that it depends on driving style and mix that determines if you need the extra octane. If you're at less than full load (engine load, not weight), then there is absolutly no benefit to the higher octane. It just doesn't come into play. If you press the gas pedal further, it does make a difference. Each and every driver should be allowed the freedom to evaluate the need for octane based on how they drive the car. For some, the higher grades WILL be a waste of money, for others, it will not.

Matt

 

"Pre-ignition is like pre-ejaculation, they're both VERY bad." This is the techno quote of the new century...really puts it into perspective. Well done SeanBlader!

Just put Premium in your MINI and in a pinch you can put in 89 or god forbid 87.

Even the Smart...car needs Premium. If you want a trick car that runs on regular get a Mustang GT.

 

SeanBlader, That was the techno quote of the century! It was the best laugh I've had in days, if not weeks! Thanks I needed that.

Dr. O.,
As always, you nail in on the head(?) with your input. This is going to sound like muddy science, but when I put 91 octane in my 99' Jeep Cherokee I get better mpg. I've monitored this lots of times and it seems pulling a pretty good pass(11,000to 12,000 feet) in Colorado, I get 1 or 2 mpg better and a touch more get and go... from my seat of the pants dyno? This might be baloney or too many hydrocarbon fumes, but it works? for me.
The reason I bought a MINI was to have a blast in a sports coupe... I'd recommend Premium.

P.S. After months and months of blood, guts and beer and restoration...a good friend and I just fired up his 63 slit-window Corvette this afternoon! TOO FUN! We drive it tomorrow... With premium fuel no less...

 

Keep it Simple, YES use the premium Fuel. If you don't want to that's fine, just ask my customer that just replaced his 50k motor that was burnt up that he had ran 87 octane since new. The valves were burnt, head carboned up, and burnt/broken ring on cylinder one. The 10cents a gal he saved wasn't worth it long run.

 

Wait, do I need to put it in my sigfile now?

 

Some cars rated for 87 may still be able to advance timing using a learning ecu so I can believe that premium would give you better mileage in that situation. However, with a more basic ecu that can't learn and is tuned for 87, you will lose mpg by using premium.

 

It's interesting in that we are talking about advancing the timing as the only way for the engine to protect itself from poor fuel. Can't the computer just open the valves less to let less air in?

 

Most current engines have the ability to alter valve timing, but not valve lift. The most advanced version of BMW's Valvetronic do provide for variable lift, but I don't know what the Mini ships with today. But with an electronic throttle, you could essentially achieve the same by electronically throttling the engine. Don't know either if the Mini does this.

This is one of those questions which people try and make black and white when it reality it is gray. If you want to keep things simple, just use what the OM recommends. But some owners may be able to use lower octane with some small reduction in performance that may or may not ever be a concern depending on their driving conditions and habits. The doom/gloom stories that you can hurt your engine or gunk it up by not using premium don't hold much water though - with a modern engine like the Mini, I don't think you can hurt the engine burning regular. OTOH, it does seem pretty silly to spend extra for a high-performance Mini and then turn it into a low-performance Kia to save a buck or two every fillup.

- Mark

 

I'd sure like to kow where you folks that talk about 10 cents a gallon for the premium over regular live. Here in Dallas the spread has gone to 20-30 cents regover mid grade and 50-60 cents reg over premium. So at 5-6 dollars per fill more you are beginning to talk about some serious money.
Just bought a 2010 MCS with 14K miles on it. Plan to use 91 octane whenever I can find it but don't see the point of "Premium" which in this part of the country is 93 Octane.

 

As mgenette stated, here in Dallas, prices for premium, which is 93 everywhere unfortunately, are sky high. I haven't seen premium for less than 30 cents more than regular in a long time. I switched from premium to regular in my '09 MC and I didn't see any difference in fuel economy. My oil lasted for 18k miles and my car runs the same as it did before. I don't accelerate super hard so that may make a difference. If I had gotten a MCS, I would never have switched from premium.

 

I had my MINI at the dealer to add a Clear bra. I got a loaner for the day, it was another Clubman S with the same options as my car. When I took the on ramp to the freeway, it didn't accelerate as quickly as mine. This puzzled me, until I filled it up prior to returning it. The dealer said that if I didn't fill it, I would be charged $5.00/gallon for them to fill it. Now I don't know for sure, but I'm guessing that most people have been refilling that loaner with regular gas and that is why it had less power on acceleration.

I did put premium in it though.

Dave

 

I'm going to be the MC voice of dissent here... I've been running nothing but Premium since I got the car, but inadvertently filled up with Regular the other day (wind was crazy, trash blowing around, distracted by Shell now accepting Kroger Plus cards for a discount). The difference is VERY noticeable on my car. Computer's indicating so far that it's getting about the same gas mileage (shows 35.8 at the moment after about 120 miles), but the car is very sluggish - it revs slower, is much slower taking off from a standing start and accelerating while driving along, have to give it more gas to get up steep overpasses that are normally no trouble at all, etc. It's bad enough that if I had an easy way to get the gas out I'd siphon it to a gas can for the mower and go refill it with the good stuff.

I see crvols is driving an automatic - maybe that's why the difference isn't noticeable. Other MC owners who can't tell a difference - are ya'll driving automatics as well?

 

Coming from a vehicle that got 17 MPGs, I am opting to go with the Premium fuel -- still costs less to fill the tank and I can go a lot farther on it!

 

When I bought my 2003 MCS JCW, that fall I started having a situation where the car when dead cold would start easily enough, but then die. On restarting it ran perfectly. The service writer told me to run a tank of regular thru it and it would clear it up - which I did and it did as well!

Since it was dead of winter I started running regular every fill-up, I noticed very little if any degradation in performance, but the fuel mileage went to hell!

I decided to just run premium from then on and never had a cold starting problem again, and the mileage got as good as it got, which was about 25-26 in winter and 28 in summer.

On my '09 Clubman S I accidentally filled it with 87 regular and again, noticed virtually no difference in performance or mileage, but went back to premium at the next fill up. It's 20c a gallon difference between regular and premium in our market area, but I feel it's worth the extra money if the mfr. considers it the right fuel to use, so I will.

For the poster who asked, my JCW was a stick, my clubby is an auto. I drive both of them hard at times, but not all the time. I guess I'm what they consider a "spirited" driver..