I put in 91 at Shell most of the time, and occasionally I'll find 94. Petro-Canada used to carry 94 but I think they pulled it recently. In any case. it's only a few bucks a tank, just use the good stuff. Your car is like your modern-day horse. Take good care of it, feed it well and keep it clean :P

 

Okay, let's set the record straight... I didn't read both pages but let me tell you this.

It is a proven fact that the best octane to run is the lowest octane you can run without pinging. (forgetting race motors)

The car will run smoother and you will get better gas mileage with a lower octane because of the rate and temperature of the burn.

Many years ago I had a sportbike that I thought I would always giver her the "good stuff". I ran 93 octane in every tank for over 20K miles. EVERY time I would reset my odometer.

Consistently I would get 150-160 miles per tankful... never changed, always the same.

Finally I read an article about the power of lower octane so I started using 87 octane and did so for the next 6K miles and again I reset the trip odometer.

Almost immediately I felt how much smoother the bike ran, you could feel it in the throttle, you could feel it in the bike, the way it ran and the way it idled.

For the next 6K miles, I consistently got 170-180 miles per tankful.

I did a lot of researching after that and found out it was truly the way it worked.

Read up on it sometime..... you'll see.


Mark

 

Mark, I had the opposite experience with my CBR600 (which, coincidentally, was the same paint scheme as your JCW!) in that it always ran smoother with 91 and I would get about 250km to a tank mixed riding compared to 210 or so with cheaper gas.

 

That's weird, I was on an F4i when I did that and continued the same experiment for many more thousands of miles on a 954.

BTW, my F4i was painted to look much like your car is now with some white. (Erion racing scheme)

Funny.....


Mark

 

That's funny, I had an '00 F4. Granted some of the improved responsiveness/smoothness could be placebo but it really did feel happier to me running 91.

 

Ya know what's funny? Both points of view have merit. Using the lowest octane recommended and the highest available. I wouldn't have come back to add anything else here until Orangecrush posted his low octane points. I figured no one would accept that position because for most people its counter-intuitive, it just sounds wrong. The fact is its actually true in most cases.

Fuel is neat stuff. Back in the day I use to concoct all kinds of fuel mixtures for the various types of race motors we built. From doctoring standard unleaded pump gas to ethanol to the most esoteric Nitro-methane blends. The secrets to making horsepower and torque is in the fuel.

Back in the day you had to run very high octane fuels in engines that had high compression ratios. This was because we were using carburetors and points ignition systems, etc. Ignition advance curves were very simple spring controlled mechanisms. We used some early Fuel Injection systems on some of the race motors but they were rudimentary, very unsophisticated. We didn't have the technology that exists today. The engines today have all their parts and systems designed and tested by ultra sophisticated CAD computers. Today’s engines are operated by computerized engine management systems that control all aspects of engine operation milli-second to milli-second. This allows even high compression motors to operate safely on relatively low octane fuels.

Back to the question at hand. Higher octane fuels are more stable, they have higher Specific gravity and higher flash points, Flame front propagation is slower and more uniform. Cylinder pressures rise at a slower more controlled rate. All these factors inhibit detonation, which is generally bad. Lower octane fuel is a little less stable, they have lower specific gravity and lower flash points, Flame front propagation is faster and can be less uniform. Cylinder pressures rise at a quicker rate and this is where OC gets a little more power. As long as you can avoid detonation the quicker rise in cylinder pressures yields more power. This also translates into a little better fuel mileage because less of the pressure yield is wasted. (This gets super technical and boring. Has to do with expansions rates of a gas and relative piston speeds, valve timing and overlap ….Yada, Yada, Yada…you really don’t want to know.)

Boy when I started to write this I didn’t realize how much there would be and how potentially boring this might be to read. Believe it or not I actually edited it down. Sorry for the ramble.

 

No man, no ramble at all.... it's posts like that, that I read back in the day to come to this conclusion.

I did a lot of research back then and wanted to know the truth because it just didn't make sense to me.

I guess we're all brainwashed into thinking we're treating our car's to the good stuff. I run 91 in mine only because I have a tune. If my car would run on 87, I would.

Like someone said, it's not a big deal because you figure if premium is 20 cents a gallon more and you average 10 gallons for instance, we're talking 2 bucks.

When you get a car that gets good mileage and you only fill up once every week or two weeks, then it seems like it's worth it.

I can't speak for Danny but I could physically see less shake at an idle and feel smoother when I hit the throttle just by using 87 (on my bike)

Thanks for the explanation.

Mark

 

I have driven BMWs all my adult life, and that is a long time. I have always used Shell Premium and have never had any issues with carbon build up or injector issues. I now have a BMW, Volvo, and Justa Cooper, and they all require premium. For the extra $3 it may cost when filling the tank, is well worth the small cost. It pays off in better milage and long term repairs.

 

Chris,

No doubt that carbon build up isn't there but I'll bet the same cleansers are put in 87 octane as well as higher octanes.

I'll bet it has to do more with the brand of gas than the octane.

Just for shiets and giggles, why don't you start filling the justa cooper up with 87 and seeing how many miles you get out of a tankful. It would be a great test.

Mark

 

Here's a link. Note the "What's the right octane level for your car?" Does sports bikes have "HIGH COMPRESSION ENGINES"?

http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm

Here's one from wikipedia (the gossip encyclopedia haha!).

http://en.wikipedia.org/wiki/Octane_rating

 

This has no scientific basis, just personal experience.

We have an R52 and R55 and both ran like crap on a tank of 87. Routinely run on 89 which is mid-grade in GA. Put some 91 through the convertible to make up for what was left of the 87 in the tank.

Also, I am not sure if this is true and haven't researched it, but a coworker said that 89 (or any other mid-grade) is an artificial creation at the pump. The stations get 87 and 91 in bulk tanks and the pumps create a half-and-half mix into the nozzle.

TH

 

So i've been reading a lot for half an hour. Everything i've read have the same conclusions.

There are no loss or gains in using higher octane rating than what your engine requires. However, there is loss in performance, mpg efficiency, harm to your engine if lower octane is used than what your engine requires.

Engine knock/pinging "Can be" harmful so it is not to be ignored.

 

I haven't seen anyone argue that a too low AKI isn't harmful. The question is what is too low. MINI contradicts itself by puttling labels on the car that say 91 minimum and providing an operator's manual that says 87 for NA and 89 for turbocharged are minimum, so I don't think a definitive answer is available.

 

So, all that said, what is the right octane to use?....All fuel comes from the same source its the additives that the manufacturers add...Shell V-power,Texaco Techron, etc.,etc.,I do believe that some stations are getting away with using more ethanol in their tanks hence the carbon build-up problems for some.I have not had any build-up at this point but I have heard from a few people that they are trying to raise the ethanol content to 15% or more UUUGH. This is one of the reasons I add Techron every 3000 mi or so to possibly ensure gas quality...Can't hurt...

 

I agree with hsaautocrosser, MINI contradicts itself. Someone should email MINIUSA for definitive answers.

 

I hope I haven’t started more problems in this thread. OC it’s nice to see you have finally updated your photo.

Guys, I was only trying to provide a little background to the discussion, not to advocate one way or the other. Maybe share a little of what I learned back when I was a "Gearhead".

Truth be told there something to be said for the guy who values economy and wants to save as much as he can where he can. This guy is probably not pushing the performance envelope too often so the detonation thing is not that critical. The car’s “engine management computer” will allow it to operate safely on low octane (87) fuel.

For the guy running Boost, like me, or if you are running a tune, buy the highest rated fuel you can. Blown motors run at much much higher cylinder pressures and much higher temperatures which make the detonation thing a much bigger deal. Sort of like wearing a belt and suspenders on your pants.

If anyone is interested, I run SUNOCO 94. I don’t mind paying a few extra bucks, but that’s me and my choice and I am completely OK with each person making their own decision.

I do want to be clear on one major point, Detonation is bad, very bad. If left unchecked, it causes significant damage to internal engine components. It’s like someone smashing the crap out of the pistons and valves with a 30lb Sledge Hammer. I’ve seen pistons with holes blasted through their tops, right into the crankcase. Anyone ever watched the Drag Races and seen the Blower explode off the engine. Very dramatic…that’s a type of detonation.

We used “Forged Alloy Pistons” in the race motors that were much thicker and stronger(3-4x) than anything used in a street motor to deal with the effects of the occasional detonation at high RPM’s in addition we ran only very high octane rate fuels or special race fuels.

I don’t know if this is interesting to anybody but I have been talking about how stable most High Octane fuel is, right. Well, back in the day, Nitro-Methane was so stable we couldn’t start an engine with it. That’s right, we needed to start our 2000HP BLOWN TOP FUEL HEMI's on some other fuel, I think it was like a gasoline/methanol blend, then switch over to the Nitro once the engine was running!

More “Back in the Day” stuff… I remember days when we would slip the guy at the local airport "a Fin" ($5) to sell us 110 octane Aviation gas to run in our 13.5:1 Rat Motors we ran on the street. Fully leaded 110 Avgas was great stuff.

Back then SUNOCO 260 was like 98 octane and it was dispensed through a "Custom Blend" pump. 3-4 grades of gasoline were actually blended in the pump. We would get the owner to "Break the Seal" on his pump so it would dispense the “Straight Stuff”. The “Straight Stuff” was like 102 or 103 octane that was “blended” with regular to yield several “mid-grades” of gas, 220, 240, & 260. I think this is where ALT Clubman’s co-worker got his ideas. As far as I know SUNOCO was and is the only distributor whoever did this. Today SUNOCO is still marketing a number of "racing fuels" with octane numbers in the low 100's. That was all back before Unleaded became the law in ‘75.

As far as Carbon Build up goes… I believe OC is correct, its usually not the gasoline that causes this “build-up”. It’s the lack of effective detergents blended into the Gasoline that are to blame. Most carbon build-up is really oil that seeps past the seals or that is drawn into the engine through the PCV valve in the intake. Oil doesn’t burn completely and this results in the majority of “Carbon Build-Up. Gasoline does leave some deposits but they are not usually a big problem.

Minimize07, mentions Shell V-Power and Texaco Techtron…These are actually marketing names for detergent additives that these distributors blend into the their gasoline at the the refinery. They are added to gasoline to scour the internal parts clean as it runs through the motor.

Like I said… Fuel is neat stuff.

 

I agree... that's why I said it's okay to run the lowest octane that YOUR car will run on. Some people's car won't run on anything less than 91.

All my point was if your car will run on 87 without any side effects (ie. pinging, etc) the lower octane choice will work better.

Tis cool, it's just a conversation.

Mark

PS. I had to change the signature, didn't follow my screenname...lol.

 

I have heard about running the lowest grade og gas but never knew why until now. Good information.

I will probably try lower octane when on the interstate when driving a steady speed. I usually run a tank almost out before stopping to fill up on my trips.

If it pings or knocks I will go back to the 91/93 stuff.

 

Then why do some engines when running lower octane have a significant amount of sludge.Could this be do from running at lower speeds and stop and go traffic.Or is it really from using lower octane.The problems formentioned in other posts seems to suggest gas problems sighted with their dealers.No divinitive answers only speculation.

 

Also,these people that do not have problems do they run their cars on the highway like I do....I have not had a problem yet and I run 93 Shell V-power exclusively and Techron at 3000 mi.Maybe by running it on the highway harder blows out the " gunk"....who knows

 

First, where did you get your information that engines running lower octane have "sludge"?

To be clear, sludge buildup is caused from oil, not poor gasoline. The main side effects from low octane are either pinging or carbon build-up.

Having said that, carbon build up is more from not have enough detergents in the fuel or having a poor tuneup.

Last but not least, the "gas problems" sighted by dealers refers to fuel pump failures... which has nothing to do with octane.


Mark

 

If you read some posts on gas quality some dealers are stating "poor gas" as a culprit to build -up problems.I don't agree with it .I beleive the problem lies with oil in the D/I engines and a poorly designed engine where the oil is not getting into the areas and it just sits and becomes mud .Partial fix is more frequent oil changes...

 

My opinion is that the sludge problem is probably being caused by the person changing the oil at the local "Jiffy Lube" type place is charging for Mobile 1 or Castrol Edge and putting in the Quakerstate crap that they get in a 50 gallon drum.

Very few sludge problems with so many Mini Coopers running around.

Mini is not the only car that uses the engine design so if it was a design problem many more car company's would have the problem.

 

Your probably right on a low grade oil being used at some cheapy place.On the other hand my local dealership has seen quite a few problems with sludge and I asked why his first responce was poor gas and letting car go for 1 yr with no oil change,,,Who in their right minds would ever let that go so long These seem to be very educated people,not kids they're grown adults

 

Not looking to argue. I just want to point out that you mentioned running on lower octane proved better for you. Unless of course i misunderstood and you meant to say 87 was the minimum required for your F4 and that it ran best and most efficient with it.

Also to follow up on what the others want to know. What is the minimum octane required by MINI for the justa and the S? I'm getting a little confused about the "It's OK", "Required", "Minimum".