Hey everyone,

Sorry if this is a stupid question or post, but I was on another forum and came across a discussion on octane and fuel requirements (related to fuel economy) and the concept of recommended vs. required identified. There was a list of vehicles on either of these two lists. Here is the link:

https://www.edmunds.com/fuel-economy...g-premium.html

My daughter drives a 2014 Countryman (non S version) that I just got a couple months ago used for her to go to college, and coming across this information, I see it is listed as REQUIRED. I asked her what fuel she is putting in, and she says the "middle grade button" which i assume is 89 octane. This is not the S model or anything so I am curious if everyone is putting PREMIUM in their MINI'S or if they have experience not using premium without engine (knock) related issues or damage?

In So Cal it is hard enough to pay for fuel at our prices, let alone $0.40+ more per gallon for a college student. I was a bit surprised to learn premium is required. Anyone not using PREMIUM and without issues?

 

Mini recommends Premium which is only $6 give/take more per fill up. It's cheap insurance to prevent your daughter from breaking down in places she shouldn't.

 

When in that situation of premium vs mid grade I used to switch up every other fill. 89 is right on the bubble. You need to monitor it for performance and mpg if you want to figure out what is best. Safest is to just go with premium and use quality gas stations that do big volume so you aren't getting stale gas.

My wifes newest car is a VW GTI and it can run on mid grade, but we do premium anyway so it can go fast when I borrow it. lol

MINI isn't really the best choice of car for budget friendly college student purposes, but that is obviously a done deal.

 

On my co-pilot's R60 justa, there's a tag inside the fuel door stating 89.
Here's a reference to help her identify approved fuel. Also, she needs to pay attention to her car's other fluids and keep up with it's other wear items. These cars are NOT drive e'm and forget 'em appliances.
https://www.centerforqa.com/top-tier-gasoline/

 

If she puts regular gas in it,It won't hurt anything, the knock sensor will tell the Engine Control Unit to retard the ignition timing so no engine damage will occur, but performance will suffer.

 

A non-S has been designed to run on 89, so run 89. No benefit for anything greater than that, just wasting money at that point. But don't run 87.

 

Thanks for all the replies everyone. It is hard to tell what is a hard rule and what isn't when it comes to the fuel. It didn't seem to make a lot of sense that a "basic" 1.6L that isn't high HP requires 91 Premium. Also, I have read, and it is my general understanding that the vehicle (as most vehicles do) have a knock sense which the computer uses to compensate for fuel octanes and such (ignition retarding). Hence, if performance is the thing that suffers then this is just fine. One reason why I didn't get an S model was to avoid complexity, issues, and the extra requirements of a turbo.

 

I just use 92 or 93. Dont want to risk injectors or HPFP down the road. You get a little bump in mileage over the 89.

 

I can understand the tuning aspect, but not sure how Octane would impact the HPFP or injectors? I could also understand a little bump in power/economy due to being able to advance timing/tuning and such. However, I still find it hard to justify a premium octane for a college student that just wants a cool car that won't embarrass her by breaking down (of which I have all ready had some trials and tribulations with electrical wise). I will tell my daughter to stay away from the 87, but the 89 is OK? Maybe alternate 89 and 91 when possible?

 

Injector made to run or designed to run on premium and the same with the HPFP when the engines are tested, that's all. Those things can be expensive to replace in a MINI.

 

The car's owners manual should state the minimum grade of octane to use and probably the preferred grade. Something along the lines of: "Do not use E-85 flex fuel or ethanol blends greater than
15% in this engine.These engines are designed to meet all emissions regulations, provide optimal fuel economy and performance when using high-quality unleaded “Premium” gasoline having a posted octane number of 91 as specified by the (R+M)/2 method. The use of 91 or higher octane “Premium” gasoline is required in these engines."

The above was not from a Mini owners manual -- I don't have a Mini owners manual in digital form, but from my Dodge Hellcat owners manual, but you get the idea.

It is not the size of the engine nor its output that determines whether the engine requires 91 or 87 but its compression ratio. Actually a 1.6l engine could have a high compression ratio because this helps improve the tractability of the engine especially when operating in its lower RPM band. The energy necessary to compress the air/fuel mixture to say 10:1 or even higher is almost made up from the initial push back on the piston once it passes TDC. And at this time the combustion process has already been started as the spark was probably trigggered at around 25 degrees BTDC.

While the engine via knock sensors can adjust the timing, retard it, this has some downsides. One is the combustion process starts "late" -- to reduce the pressure created in the cylinder -- but this means the pressure from the burning of the fuel is pushing on the piston that is located at a less than ideal position to make the most of this.

As best I can offer is when riding a bike one just knows when the ideal time to put his weight down on the pedal. If one forces himself to delay this one instantly recognizes how this really reduces the amount of forward motion is generated from that delay.

Yet another problem if too low an octane gasoline is used is the engine controller may not be capable of adapting timing to accommodate the too low an octane of gasoline. The engine designers set a minimum octane requirement and the engine controller is able to adapt to this but it is not intended to adapt to any old "goat" (you know what) gasoline some customer wants to run.

There is at least one other downside to running too low an octane and that is combustion starts later but it also finishes later. The result is this raises exhaust gas temperature. Every engine component exposed to exhaust gas runs hotter. The exhaust valves in particular are a concern because they run pretty darn hot even if the right octane is used. The O2 sensors also run hot -- they have to to work -- but they can run too hot. Likewise the converter which also has to be hot to work can be too hot and this can cause it to degrade.

Really it is false economy to run too low an octane of gasoline. While one may not have to say run 91 and can instead "get by" with 89, running anything below this is or should be a no no.

 

Too risk being labelled Captain Obvious, why not just read the owner’s manual? If you don't have a paper copy, google it and you will find a download link for the PDF. My manual states that for a Cooper S you need 89 octane *minimum* and even states that long term use of 87 will severely impact the longevity of the engine. 91 is recommended, thus higher ratings are a waste of money though you can buy it if it makes you feel good! :-)

Non-turbo N18 engines accept 89 recommended and 87 MINImum.

Google led it or read it. Straight from the manufacturer’s mouth. Shouldn’t that be gospel enough?

 

once again the octane discussion and 'seat of the pants' reasons for running high octane even when not required

suggestion: do a little research into what the heck "octane" MEANS in relation to an auto engine. it won't make the car go faster, is not 'cleaner', won't save the HPFP ... and for the most part will only make a difference if you have a tendency to go 'full throttle' when accelerating.

My current daily driver is a Focus ST which like a MINI S has a turbocharged 2(ish) liter 4 cyl engine mated to a 6 speed. The ST supplement to the owner's manual discusses the use of various octane ratings and mentions the importance if the engine is routinely run under HEAVY LOADS (to avoid pre-detonation issues) but also proves a table of available HP from "low" to "high" octane and the range is a few HP .... around 2% and TORQUE isn't impacted at all . . . .

btw my 79 has NO computers and IS tuned to need 92 or more. Wanna have a real seat of the pants experience of negative impact of too low octane when it MATTERS - that is there's no COMPUTER to adjust the ignition to control pre-ignition based on knock sensors)? Come for a ride with me with some 89 octane: knock that sounds like the pistons will jump out the bonnet and no power (aka PRE-IGNITION) and dieseling .. (aka the engine doesn't even NEED spark cuz the fuel self ignites just from compression ..... what does OCTANE rating have to do with that????) Experienced this twice. First time was the one and only time I tried mid grade fuel ..... finishing that tank and getting high test back in ended the problems. Only repeat was the time I saw an independent station that claimed 92 octane alcohol free ...... same results. Went back to name brand 92 (with alc) and no more problems . . .

 

Thanks for all the good information! Yes, my understanding about Octane has nothing to do with HPFP or Injectors, etc. It is the science of the burn and compression, etc. Engines and Management systems are designed around this or not... My original question had a link to lists that were either "RECOMMENDED" or "REQUIRED" premium. The 2014 Mini Countryman (non turbo) my daughter has is listed on the "PREMIUM REQUIRED" list. I don't have the manual to read for gospel. It seems that there is some conflicting information on if PREMIUM is recommended or required. So far, the majority seems to indicate it is not REQUIRED, but RECOMMENDED (which I could see how every vehicle could be recommended). If it is not required, then this is my point/concern about wasting money for Octane not needed in this case for a college student and "cool" transportation to job/work...

In General (which is applicable to my daughter needs): Seems like 89 is "required" and 91 is "recommended" and 87 is to be "avoided".

Agree?

 

Along with running the proper octane I highly suggest using a Top Tier fuel. Look it up. Running a discount higher octane fuel that doesn't have the correct detergents or additives can cause build up and damage to several parts of your drive train.

https://toptiergas.com/licensed-brands/

 

If the engine is tuned for higher octane the engine will produce more power with the higher octane fuel because the engine controller can use more ignition advance so combustion begins sooner and generates maximum pressure when the piston is better positioned to convert this pressure into mechanical energy.

At WOT the engine controller can ignore the #2 sensors, go open loop, and add more fuel and couple this with cylinder filling is less effective at higher engine speeds so combustion pressure in the cylinder goes down. Thus the tendecy to detonate is reduced. But even under these conditions the right octane of gasoline should be used because the engine will operate at lower RPMs, higher throttle opening, thus better cylinder filling on its way to WOT.

It is at part throttle low engine speed which results in better cylinder filling thus higher combustion pressures where the proper octane can make a difference. The engine controller can use more timing advance without bringing on detonation. In some cases the auto maker states the engine is tuned to run close to or even at incipient detonation because the engine is just more efficient/responsive.

To run the recommended (or in some cases required) octane of gasoline is just good sense. The engine gets to operate more efficiently, so it gets the most energy from the burning of the gasoline, exhaust gas temperatures are lower, the engine is cleaner running. And one gets the performance and tractability he paid for. Very likely the engine gets better fuel economy with the right octane of gasoline so even though it costs more the actual difference in cost could be nil. That is running a lower grade of octane might save some money at fill up time but the fill ups occur more often.

What your '79 manifests is pinging which is not the same as detonation. Pinging is a factor -- to name two of the factors involved -- of combustion chamber shape along with combustion chamber deposits. Detonation is a silent engine killer. One may not be aware of the engine experiencing detonation until he runs over a piston or rod or even the crank from a blown engine.

 

From the 2014 Countryman official owner's manual (link to manual after pic)


2014 Countryman Owner's Manual -> https://www.miniusa.com/content/dam/...man_Manual.pdf

Funny thing is that they have changed the wording from that in my '11 Countryman, where they specified different minimum octane ratings for turbo and non-turbo engines.

 

Where octane can affect injectors, etc., is premium fuel generally has more detergents and thus this tends to keep injectors cleaner along with other surfaces exposed to the combustion gases.

The HPFP of course operates at very high pressure and the fuel also serves as a lubricant for the pump's moving parts. High quality "top tier" gasolines are refined to a higher standard and thus are a bit better in cleanliness and blending. The HPFP can benefit from this.

As for what grade of octane your daughter should use in the car, what the majority believes/says doesn't matter.

Consenous is not science.

If you want to be sure if premium is recommended or required you need to consult the owners manual for the car. (The owners manual also has useful info on other subjects, like service intervals,where the vital fluid reservoirs are and how to check the levels, maybe how to change a flat tire, etc.)

After consulting the owners manual your daughter should then use the proper grade of octane. If premium is not required she can run a lower grade -- as long as she doesn't pick a grade below the minimum. The engine will not be as efficient thus gasoline consumption can go up and there may not be as much savings as one assumes based on the price difference between the lower and higher octane gasoline.

Advise her to also buy gasoline from a busy station to ensure the gasoline is fresh.

 

Preach it, brother! :-) Opinions are like noses. Everyone has one. I'm not sure why we continue to have debates (the OP's original post was a pretty simple ask) but we do anyway LOL.

 

No. Your '14 has different requirements than the ones I posted from my '11's owner's manual. I have posted the correction in another post on this thread. I recommend that you bookmark this link. It is a download repository of all the MINI USA owners manuals: https://www.miniusa.com/owners/tools...r-manuals.html

 

Thank you for the link to the manual and the screen shot! This is what matters as people on this thread have said... Everyone has opinions and some misapplied science. Regarding fuels and such, my understanding is that just because it is 91 Octane doesn't mean it has magical additives that are better or more than the 89 Octane would of a given supplier. Octane is the only difference.

There is much discussion about why there is different Octane and tuning for such, but this is not the point being sought. I certainly understand the finer points of this and it is good to hear what may be fact/fiction/belief. I see MINI Recommends, but doesn't Require 91, hence from my original question where data was posted and linked (EDMUNDS) about recommended or required lists seems to be in error. MINI should be on their recommended list, not required.

Or perhaps it is my interpretation of PREMIUM. Does this included 89 and 91 only, but not 87? Does premium refer to top tier, not sub tier? The words seem to be a lot of semantics.

Again, thanks for the data from the manual as this makes the most sense. It even says the motor is knock controlled which was my understanding. However, I suppose it is not knock controlled down to 87 Octane grades.

"The engine is knock controlled. Therefore, you can refuel with different gasoline qualities"