So, ok, pardon my ignorance, but does my Justa have that compression ratio? (10.6:1)

 

Yes, as I understand, the compression ratio in the Cooper R50 is 10.6:1. According to the Googles, the R53 has a compression ratio of 8.3:1

I don't know if the R56's are any different.

Edit: A few links I found say the R56 Cooper has a ratio of 11.0:1, hopefully someone knowledgeable here will chime in

 

Thanks for researching this, I have the R55 (Clubman) 2010.

 

No problem. You should have the same compression ratio as the R56 Non-S. Give it the good Gas!

 

Awesome, thanks for putting up with me!!!

 

Your paying a little more up front will end up saving you a lot more in the long run.

 

Agree!

 

most turbos have a lower compression. Specs for 2011 JCW Clubman says 10:1 compression. Using higher octane gas than what is needed offers no benefit, and can cause issues with "coking" or carbon build up. Octane is added to fuel to resist detonation (so a high compression engine will not "fire" before it is supposed to). It makes no more power than regular gas. Bike guys have this conversation every 3-4 minutes... haha

 

Are you trying to say that because turbo cars have lower compression pistons they don't need high octane gas?
Or are you specifically targeting the JCW model with it's "low" 10:1 compression pistons that it doesn't need the high octane stuff?


If the answer to either of those questions is "yes", please don't offer any more advice.

 

Octane isn't "added", Octane is what gasoline is, i.e. the chemical name of gasoline. 100 octane gasoline would be 100% iso-octane. But the gasoline we buy is really a blend of hydrocarbons that is mostly iso-octane and is blended to act like 87, 90 or 92 iso-octane, depending on where you are.

Dave

 

so is 110 octane 110% iso-octane?

 

The problem is, the "10:1" and similar figures only describe the static compression ratio. The static CR is determined simply by things like bore, stroke, and combustion chamber volume.

But an engine's octane requirements are determined by the dynamic cylinder pressure during compression and combustion, and forced induction makes a huge difference in dynamic cylinder pressure.

If you have a naturally-aspirated engine with a 7:1 static compression ratio, you can probably safely run it on any crap gas that will burn. But take that same engine and attach a turbocharger running 25-30 psig of boost, and your fuel requirements will get real strict real fast, even though the static CR is still 7:1.

And 10:1 isn't "low compression" to begin with. If not for things like proper cooling, good combustion chamber design and aluminum cylinder heads, that kind of a ratio would probably require premium gas even without the turbocharger adding to the dynamic cylinder pressure.

 

I just knew some smartass would say something like that! OK, I'll go into a little more depth.

It is possible for an octane number to be higher than 100 because of the varying methods they use to calculate the octane number.

Octane is also a measurement of the resistance of a fuel to cause engine knock, or pre-ignition. You can add chemicals, methanol, ethanol, toluene, zylene, methyl tertiary butyl ether and tetra-ethyl lead to iso-octane that will push the resistance to pre-ignition to higher levels than just octane can provide, hence the possibility of higher numbers than 100 octane.


Dave

 

that's cool. My point was, using higher octane than needed offers no benefits. If the Mfr calls for 89, or 91, using 94 isn't better.

 

I have a 2007 MINI Cooper PW/PW. I used regular octane before and received a warning light on the dash. I had to bring it into the dealership for a look. We had to add octane to correct the problem. Don't buy less than premium. Your MINI will know the difference.

 

I am buying a used 2007 Mini Cooper base, and was wondering if anyone knew how to tell if the previous
owner used 87?
and if they did will putting in 91 fix anything the 87 grade hindered?
thanks

 

Good question.. I don't think theres any way to tell what they ran in the car prior unless you're buying from the previous owner
I bought a 2013 R56 a couple months ago and I have been running premium in it ever since. But I bought it from a dealer so I have no Idea what was used in it for the previous 49000 miles.

 

I used 87 octane once, and I'll never do it again. It chugged like the MAF was bad.

 

Where I live (North East) Premium cost more like 50c more than regular so your looking at more like $6 per fill up. Depending on how much you drive it can add up. That said I use 91/93 but if I see that it's close to a $1 more ( happens sometime when traveling) run a tank of regular and not loose any sleep over it. I don't think it's a critical in the N12 as the turbo.

 

Just as important is to use top tier quality fuel, it won't have as much water & contaminants in it.

 

LOL! .20 cents more?? I wish! Right now the cheap stuff is 2.32 and the premium is 2.95. But the extra 7 bucks a week isn't going to kill me so I'm going with at least mid grade to premium on fill ups, not too worried with the extra cost. We LOVE this Mini! I don't know if I've ever loved a car so much.

 

Cheap bastards! Just buy the good stuff, like the manufacturer recommends.

 

I had a 2010 non-S MINI for about 8 years, and never used premium, with no problems.

 

I ran 87 once, and it was fine, but I noticed a little bit more hesitation when letting off the clutch from a dead stop. Probably the computer getting used to a less-than-expected octane level, or something. Generally, you don't want to be cheap about gas, thanks to the ethanol content, which WILL gum up your intake over time. At least go with midgrade. I normally run REC-90, 91 or 93. I know that sucks to hear when we're living in a completely self-made oil crisis, but at least you can get 40-50mpg out of these cars. It evens out somewhere, I'm sure.

 

It's not recommended by BMW, but my sister has used nothing but regular in her 2018 Countryman S, and it is doing fine. She uses mostly Costco gas, which is "Top Tier," and should have the additives DGI engines need to keep the valves, etc. clean. The mildly tuned, low boost 189 hp MINI engine should not need premium, when more powerful 2.0 turbos from other companies use regular.