Sure you can run with the cheap stuff, but its a small price difference considering i think most of us buy these cars for the amazing performance they offer. Its like, sure you can live off of mcdonalds, but you arent going to live healthy (or long). So why chance it?

 

http://www.consumerenergycenter.org/...s_premium.html

http://www.sciam.com/article.cfm?id=...tion-premium-g

 

Interesting links. However my thinking goes like this...I fill up weekly. I put in somewhere between 12 and 12.5 gallons per fill up. That comes out to about $2.50 per week extra to do what the engine designers/manufactures suggest. Then I walk in and buy a pint of water for a buck.

 

Just out of curiosity--if MINI determined regular gas was used (89 or even 87), although it is NOT recommended, would MINI honor the warranty on the engine or other related parts?

As expensive as repairs have become, I'm not about to jeopardize any warranties.

 

The manual says:
I think that implies that exceeding those numbers could void the warranty.

 

GregO, if your car is running fine on regular old regular then more power to you. I know that I saw an increase in roughness in the idle when I was forced to use 90 octane for a while because of the area I was in.

I do find it interesting that the articles you linked to were about people using premium in cars designed for regular. The first article (just scanned the second) talks about using fuel higher in octane that what the manual recommends. It says nothing about using lower than what the manufacturer recommends.

 

Grego - did you read the links you provided? The first is about using premium when the vehicle manufacturer recommends regular, and the second article states, in the beginning of the second paragraph: "First and foremost, premium gas really is a better fuel in terms of the power it provides in the right engine" That would be all MINI engines.
If there's an article you're aware of that addresses using regular gasoline in an engine designed for premium, without any reduction in performance, please provide that link.

 

Um, I'm talking about octane, not ethanol.

 

Around here, to fill up 12 gallons with 93 vs. 87, it is only a little over $2 difference in total cost. Im stickin with 93.

 

if there were damage due to knocking or carbon build up you can be dang sure it won't be covered under warranty if they prove you weren't using the recommended gas. Dealerships can and have taken fuel samples to find out what type of gas in in your tank if they suspect bad gas.

 

miniclubman, both articles pretty address everything you're asking about. While I love the MINI, I hardly consider the Chrysler and Peugot powerplants as being the "right" engines for premium. Advanced engines? Relatively, of course. So, I'm not saying they're not advanced, but they're not exactly Formula 1s where every minor advantage counts. Now, if I were tracking my MINI, yeah, I probably would run higher octane on track days. Greg

Pretty cool test: http://www.jackphelps.com/frontier/dyno2.htm
Now, we just need some MINIs dynotested to have real data.

 

The MINI compression ratio is 11:1. The "normal" compression ratio mentioned in the Scientific American article link is 8:1. (MINI has a 37% higher compression ratio then the referenced 8:1 ratio.)
This difference in compression ratio is substantial, and is why you need higher octane to take advantage of the MINI engine's potential. Lower octane fuels will ignite when compressed before the spark plug ignites the fuel mixture, hence the term "engine knock", which is pre-detonation of the fuel mixture under compression. Higher octane fuels will not do this. While I'm sure a MINI will run, more or less, on any gasoline, it certainly will benefit in both performance and fuel economy by using the recommended higher octane fuels.
It's true that the MINI engine management software detects "knock" and adjusts for inferior fuel. This adjustment robs you of both power and fuel efficiency. As I said before, it's your decision what fuel you want to run with, I'll stick with the fuel that gives me the best engine performance.

 

Not mine.

 

To each their own.

 

The manual doesn't specifically say what octane rating would void the warranty, but it does say that the minimum requirement for the car is 87.

 

Let's see, direct injection engine with a greater than 10:1 compression ratio and you don't think that is an appropriate engine for Premium? Wow, there aren't many engines that would qualify.
Last I heard, F1 cars don't use Premium gasoline.

 

It's a simple analogy. If you want a more-closely related example, how about NASCAR Cup cars boasting 12:1 compression ratios? Yeah, yeah, it's a different "formulation". Point being, even the smallest advantage can help in such a case. I only do this to stir the pot because some of you get a wee-bit extreme.

Regardless, I would honestly like to see the empirical evidence for dyno-tested MINIs - I figure somebody must have done it, but I've yet to find any MINI-specific records... yet.

 

From what I've read, NASCAR uses 112 octane.

Yea, following the mfg. recommendation of using 91 octane is an extreme position.

I'd want to see that evidence before I made the switch to a lower octane, rather than needing it before using what is recommended.

 

On my last two cross-country trips, I've purposely alternated between the lowest grade I can find (usually 86) and the highest grade I can find (usually 93). I would run the tank down almost to empty, and then re-fill with the opposite of what I used for the previous fill-up. I didn't notice any difference in fuel economy that correlated to fuel octane.

Here are the numbers from one of the trips, taken in June from Virginia to California:

93 octane - 29.7 MPG
87 octane - 30.9 MPG
93 octane - 29.7 MPG
87 octane - 28.3 MPG
91 octane - 28.3 MPG
86 octane - 29.4 MPG
91 octane - 29.0 MPG
87 octane - 31.3 MPG

I went at least 330 miles on each tank, so there wasn't much mixing of the different fuel grades.

Now, some things to keep in mind for those numbers:

1) It was almost all highway driving, so there was less danger of knocking/pinging since most of the driving was steady-state cruising.

2) The temperature was all over the place, from the mid-80's in Virginia to 115+ in Arizona.

3) The speeds also varied pretty widely. Most of the time, the speed limit was 65-70 MPH, but much of I-40 starting in West Texas is 80 MPH. Also, there were stretches were either the speed limit was 55 MPH or there was construction/traffic that slowed things down.

4) My car doesn't have any engine mods that raise my octane requirements above what any bone-stock 'S' would require. It's possible that if I had a smaller supercharger pulley, or had raised my static compression ratio as a result of cylinder head mods, that my numbers could have been very different.

On subsequent trips, I *have* noticed that I get much better fuel economy at 55-60 MPH than I do at 70-80 MPH. I figure the engine is probably less efficient at the higher RPMs, but I suspect the main reason is that aerodynamic drag increases greatly the faster you go. Going from 60 MPH to 80 MPH is only a 33% increase in speed, but aerodynamic drag increases by 78%. And for the parts of I-40 where I was going 90 MPH, the drag is more than *double* the drag at 60 MPH. (225%)

 

Here it is a 30 cent difference. That comes to $3.60 per 12 gal fill-up. The psychological rewards of penny-pinching is powerful.

Thanks for the data. Confirms what I have noticed in my MC. I never quite believed those who said the savings of regular gas would be offset by worse gas mileage. Performance possibly, but nothing I have noticed. Maybe someone will do the dyno test?

 

For what it's worth, that's rather poor mpg, given steady cruising with "most" of the time running 65 to 70 (or were you in excess of that?). I took my S from Houston to Florida and back, and was rather unhappy to get only 33mpg (all 93 octane). I had expected more with a steady interstate cruise. I was a little mollified by the knowledge that I was cruising at 80 to 85, with somewhat lower numbers during heavy rain.

A little OT, but just curious why your mpg would be that low for an R56.

 

The top article addresses people putting premium fuel in their car that doesn't recommend it (Aka, a Focus, tuned for 87 octane, doesn't see any benefit from someone using 91 octane in it). This is no surprise, and most of us already know that.

The Recommended octane in the MINI is 91. This is because the engine is TUNED to use 91. I don't understand why people can't grasp that concept.

It's like people that go out and buy a Porsche 997 Turbo and put 87 octane in it. . Yea, you can afford a 143k dollar car but you can't afford $3 a week more to fill up? Put whatever you want in your car. It's YOUR car. Don't ask people what the recommended milage is if you don't like the answer though. BMW doesn't get paid by Exxon for recommending 91 octane in their cars. They run high compression because they produce high performance cars, and figure that anyone buying a car for over 25k dollars (Known for it's performance) would probably rather have higher performance than worry about penny pinching.



These are the same people that think they're somehow saving money by buying a Prius. Yes, it's true, the prius gets great milage. It's also true that it costs 25% more than an equivilent car that gets 90% of that milage. The average person would have to keep their prius for over 10 years to realize any gas savings. It's all in the mind.

I myself didn't' spend $15K+ on my engine so I could lose 10% of my HP because I'm too cheap to use the gas that the manufacturer recommends.

 

Sorry - I don't have an R56, and I didn't realize until reading your post that this was in the 2nd-gen forum.

Mine's an R52, and on that particular trip, I had the entire car packed full with 320 pounds of stuff, and the top was down for a good part of the drive (back to that whole "aerodynamic drag" thing again...

R56 numbers would certainly be higher.

 

Ah... In that case, you got GOOD mileage!

 

Since you have an R52, you are talking about an entirely different engine. I don't think you can apply that to the R56. Also, you would need to include the speed, temp, altitude, and driving conditions (traffic, hills, construction, etc.) data for each octane if the numbers are to be of much value to R53 owners.