There are ONLY 2 grades in most of the US for automobiles. 87 and 93. Anything else is either a mix of the 2 or has additive to take it to higher octanes. The ONLY difference between top tier and everyone else is the additives.

And finally, ethanol is not good, it lowers the energy level of the fuel resulting in lower fuel economy. It is good for 1 thing, lowering emissions.

Run what the manual calls for, see what additive package your car likes best and run it (even if not top tier), and avoid ethanol for better performance and fuel economy.

 

It never ceases to amaze me of the blatent stupidity out in the world today.
the "BUILDERS OF THE FRIGGIN CAR" states that you should use 91octane!
HELLO!! THEY BUILT THE CAR! they are telling you what to use to get the most benefit from the product you just purchased.
if you are that much of a cheap *** and worry about that extra $2 at the pump between regular and premium get rid of the damn car and buy some econo box piece of crap!

And to all you "my car still runs the same on regular" NO IT DOSENT! the timing is pulling back (ie) power loss! DUH!

 

amen brother!

 

Sad. Today I stopped in the local dealership to look at the Clubman and lo and behold here was a gentleman talking to one of the Advisors about fuel.....the advisor said that it was no big deal and the car would run fine on regular. Just goes to show that even a MINI dealer will say ANYTHING for a sale. If my wife had not been with me (she gets anoyed when I get on a tear) I would have explained that there is a good reason the manufacturer recommends 91+.

 

you should have said something. I hate the fact that most car salepeople arent even "car guys". the expression would have been priceless.

 

Dude, you need to chill. The builders of the car have already said they will run fine on 87. They obviously recommend 91 for "ideal" performance and reduced emissions. If you feel your car runs fine on 94, use it; 93, use it; 91, use it. If you feel it runs fine on 87, use it! For all I care, folks can dilute your gas with water - it's your car -do what you want with it.

Until you show me some real tests (not this - "duh, I can feel it runs better" crap) displaying a "significant" increase in power, etc., using 91 versus 87, I'll remain a disbeliever and keep running mine on 87. Does retarding the timing affect power? - probably. Significantly? Doubtful, but... I haven't seen that data yet. Greg

 

its a twelve gallon tank your only saving like 4 dollars by putting the crappy gas in it instead of the premium so y not just take care of your vehicle and forget about the extra couple dollars

 

Just for giggles, I ran a full tank of Shell 100-octane through my car a few months ago. Couldn't tell a bit of difference compared to the 91 I normally use (best I can find in this part of California).

Granted, I wasn't racing the car, and my engine's stock. It's possible that if I had put the car on a dyno, the 100 octane might have made a difference at 5000+ RPM and wide-open throttle, but for around-town and highway driving, it felt exactly the same as 91 to me.

 

I hope this helps comprehend the difference in octane ratings. Just my two cents.
URL: http://auto.howstuffworks.com/question90.htm

 

Use "Top Tier" gas in your MINI. It'll like it in the long run, as there will be less deposits.

http://toptiergas.com

 

I've worked for a major oil refining company for 35 years and I can tell you the different grades of fuel can make a difference the way your mini runs.... The high performance engine will fire better with the higher octane. The regular will burn almost the same but will not be as hot at combustion as the 92 or higher grades of fuel. The lower grades of fuel will form deposits of carbon on your engine coponents. If your driving for fuel saving only burn the 87....if you like performance then burn the higher grade...

 

Is this a good enough reason to run the proper octane gas in your car?





This cylinder has a cracked ring so the damage isn't as appearent, but you can see the spots of gold on the piston head from detonation.



It's true, the car can and does pull timing, but it can only do so much, and it has to detonate first for it to know to pull timing. For what it's worth this was on a car running 91 octane gas from Chevron, the issue was traced back to bad gas (Every car that filled up at that station had major engine issues, including a few blown motors).

Feel like using 87 octane? Have fun...

 

Lower grades of fuel don't burn colder than higher octane fuels. Higher octane gas simply has a higher autoignition temperature. In high compression motors or motors with high cylinder temperatures, unburned gasoline can combust causing a shockwave which impacts the primary flamefront (See the gold V shaped spots on the pistons above). This can cause massive damage to the cylinder chamber and piston head by increasing cylinder pressures exponentially.

Almost all modern engines have anti-knock sensors, but it has to sense a knock before it can dial timing back enough to compensate. In some cases this means whatever damage would have been caused has already been done. In rare cases the engine can knock so bad that even with the timing retarded as far as the engine can compensate it still knocks. It's times like these that you see results like the photos above.

Information on Octane Ratings

Information on Engine Knock (Detonation)

Is saving $3.50 a week really worth chancing it? Come on guys, skip a Starbucks that week or something. Gas is $4.15 a gallon here, I'm a 21 year old college student and I somehow manage .

 

I think the main theme we need to pay attention to in this thread is fuel quality. 91+ octane gas versus 87 octane gas...I think for anyone who values their MINI and wants years of motoring harmony this is a no-brainer. As Rustyboy155 states the $3.50 extra a tankfull is an acceptable investment most of us will take to keep our MINI operating smoothly.

GregO,

you may not be seeing any differences at the moment, but remember this forum when your performance really starts to drop off because of the deposits/damage that you may encounter in a few years. You are correct, it is your MINI, but I think the reverse is also true to your point; until you show me that lower octane fuel does not cause damage to our MINIs, it is wiser to follow the manufacturer's directions and use the 91 octane gas.

GregO stated:
"Until you show me some real tests (not this - "duh, I can feel it runs better" crap) displaying a "significant" increase in power, etc., using 91 versus 87, I'll remain a disbeliever and keep running mine on 87. Does retarding the timing affect power? - probably. Significantly? Doubtful, but... I haven't seen that data yet. Greg"

Funny how you demand those of use promoting the use of 91 octane gas "show you some real tests", but you don't hold yourself to the same standard. You even admit that the lower octane retards the timing-thus decreasing power...it may be by a larger margin than you think.

How about show us some "real tests" that support your point of view. I think Rustyboy155 has already submitted pretty good evidence in support of following the manufacturer's recommended fuel quality.

 

lawmann,

I'm not trying to be a PITA, but I'm expressing some healthy skepticism. The MINI manual even states that using 87 AKI or better will not cause any harm to the engine (at least not during the warranty period ). I'm still trying to locate evidence to support these claims either way. The cynic in me suspects the data is rare because it is a "show" to at least some degree. If there was truly that great a benefit, you can bet it'd be marketed to that end with substantial proof backing it.

Sorry, but a couple pictures from one engine displaying some wear and tear is hardly adequate. What octane was used? 91?. Bad gas diagnosed how and by whom? Maybe racing had more to do with it? How old is the engine? How many miles? What's the compression ratio? Which oil was used and how was the engined cared for otherwise? What about spark plugs/spark? etc., etc.??? If that was the result of 91 octane, I'd like to see several samples across several octane ratings to compare 87, 89, 91, and even 93. I know it's asking a lot. Does it all result in premature vehicle death or does it all really just not matter in the long run?

Greg

 

To be fair, Rustyboy *did* state in his description of those pictures that the damage was the result of "bad gas" from one particular station, bad enough that "Every car that filled up at that station had major engine issues, including a few blown motors."

I don't know what exactly was wrong with the gas, but it's probably not fair to hold those pictures up as the result of simply using too-low octane gas - there was obviously something else much more wrong with it to cause (presumably) short-term serious damage in so many cars.

 

ScottRiqui,

Point well taken on your observation. I think we can all agree that poor quality was the problem, agreed-far, far more exagerated than what 87 octane would yield on a single tank.

I think each should weigh the benefits/consequences for which octane fuel they use, I for one will stick with 91 or higher octane. The added expense I simply chalk up to being "insurance" for my engine. Using strictly "Top Tier" fuel keeps the odds more in my favor of not getting a tank of "crap".

Happy motoring to all!

 

Your not a PITA. This is what this forum is for, educated debate and learning.

 

GregO,

I think the 91 Octane is a requirement of the Cooper S. I think the "Non-S" Cooper can run on 87 octane.

 

Cheap *** bastards purchase a $25K auto but cringe at spending the extra $3-$4 bucks for premium gas at the pump.

 

There are several good points here...

The manufacturer reccomends 91....that's what you should use. Now if your local station has run out of 91 and only has 87....well, you're okay to use it for a tank and not loose any sleep. But go back to what is reccomended when you can.

Loss of power will not REALY affect most of us (unless you are racing)...but increased maintainance costs will hurt anybody...y'know the ounce of prevention thing...

The costs are a bit different up here in Canada...about $7 to $10 per tank more for 91....once per week (with avg fill up of 50 liters) = $364 to $520 per year...more expensive, yes, in the short term...but STILL worth paying the difference....vs. how much to correct engine problems once they occur?

Also the build up of carbon in an "87 motor" will continue to reduce its efficiency by an increasing amount...further decreasing fuel mileage and using more in fuel to cover the same distance....thus defeating the purpose of spending less on gas.

If you want to save gas....Check the air pressure in your tires regularly, keep your filters (oil/air/fuel) clean and change your oil on schedule....nothing new here.

just my two cents (Canadian)

 

Not sure about the MINI, but most newer cars with knock sensors also richen fuel mixtures when the knock sensor dials back the timing. So, although running 87 octane will *probably* not harm the engine and you will save money up front, you will lose gas mileage (there goes the savings!), power, and efficiency. It hardly seems to be worth the debate.

 

When

 

When I bought my '06 S, they told me that since we didn't have 91 octane in TN, to mix it half and half between 93 and 89 and that would do it. Try to remember; but, if not I'll fillup with 93.

 

The octane rating of the gas was lower than it should have been for 91 octane gas. (Fuel was filled improperly in the tanks, it was closer to 88 octane).

The engine had 29,700 miles on it.

As you can see from the CRACKED PISTON, the engine had a bit more than just "Wear and Tear"

Oil was changed every 3-5k miles with MINI Factory Oil. The car was inspected almost monthly and several compression tests were done over the life of the engine, all were consistent with a healthy engine.

Engine compression was factory, there were no internal modifications to the engine.

Plugs were NGK 2 step colder plugs.

Intake temps were under 80

Air Fuels were between 10.5 and 11.3

The engine had 2 HPDE's on it.

Would a stock toyota Camry that filled up there have had any issues? Unlikely... Would a stock MINI? If it was driven carefully, I doubt it. It would have detonated a bit, but nothing the pinging should have been dialed back by the ecu.

A combination of crappy gas and inaudible pinging from aggressively driving the car were the cause of the failure. Had the gas been 91 octane there likely wouldn't have been any issues. I could tell something was up by the time I got home. The idle sounded off and just from the sound of the engine I could tell there were compression issues. The engine held together for almost 400 miles of heavy pinging though before the piston finally failed.

If you want to use 87 octane against the manufacturers recommendations have fun. I guarantee you if your engine fails under warranty and the dealership tests your gas and sees 87 octane in there they're going to deny warranty coverage. I don't give a crap what your salesman told you you could put in there.