My high so far in 4k miles is 45.4 mpg, never less than 40.
Slowing down definately helps.
It'd be nice also if 6th speed was geared higher.

 

I'm only on my 3rd tank but so far the MPG is better than I hoped.

1st tank: 35MPG calculated
50% Interstate (73mph)
30% rural roads
20% city

2nd tank: 36 MPG calculated
60% Interstate
30% rural roads
10% city

AC on about 50% of the time, twisty rural roads driven "assertively"

I'm guessing from those figures that 90%+ Interstate driving would yield 39-40mpg.

Note: OBC was within 1 mpg of actual calculated both tanks.

 

How are you calculating this? Manually when topping off the tank and resetting your odometer or using MINI's onboard computer? I never use the OBC. In fact I'm not sure where to look for those figures. Your mpg are far exceeding MINI's own ratings.

 

Well I drive my car pretty hard (fast acceleration and never much cruising...i vary speeds often), I'd say I drive spirited about 95% of the time, but I still average 38mpg...thats with city and highway.

Pure highway I can hit 43 mpg, and just city with driving it hard i usually end up with 37...now I have gotten 35 when really pushing it all around city driving....im just shocked at ur numbers


Do you use much AC with your city driving? I never do because I can't stand how much it affects performance (highway is barely noticeable tho)

Also if you are looking to see what your OBC is giving you, just go to your radio controls, push MENU button, then push in rotating *** to select Computer and it will show a whole list of info

 

My obc usually reads about 2mpg better than calculated.
I am driving for mileage, usually.
It's usually not that exciting.

 

I probably could have settled this argument down if I had chimed in earlier.

I am an experienced Engine design and development engineer (many years with Chrysler) and can summarize what running lower than specified Octane will mean to the operation of an engine with a good knock control system:

• While it is true that the knock control system must let the engine knock in order to detect it, knock is not an all or nothing phenomenon. These systems are good at detecting borderline knock which is tougher on pistons than no knock, but not so tough that the engine can't pass a general durabilty dyno test running at this knock level. It is good to avoid running on the knock limit, but it won't appreciably effect the engine life.
• On the other hand, the knock control system relieves knock by retarding the spark timing to the point of undedectable knock. This reduces fuel economy and raises the exhaust temperature. The higher exhaust temperature could effect the durability of the exhaust manifold and/or turbocharger. This is only a problem at near full power, where the ECU is already running the engine rich to control exhaust temperature. BMW either has to allow a slightly higher exhaust temp when knock-limited, or add even more fuel (this is what they probably do).
• None of this matters much when you drive at light loads, since knock tendency is proportional to load. Also, your engine requires a lot less Octane when the air temp is cool and/or humid. You can generally get away with less Octane in the winter than the summer.

Dave

 

Just did the first fill on my '08 MC m. OBC said 34.2 mpg; hand calculated at 31.4. Driving was pretty much all short trips in the city with no particular attempt to drive economically. A bit lower than I expected, but this was on the dealer tank of gas which certainly had ethanol in it and may not even have been premium. I refilled with premium, no ethanol.

Fuel gauge had two bars left and OBC said 90 km range remaining, but tank took 49.5L out of alleged 50L capacity (13.1 out of 13.2 gal) even before it clicked off. So either I was running with one tenth of a gallon left or the tank holds more than advertised. Next time I'll take the low fuel warning as a signal to fill up immediately without trusting the OBC's range figure.

 

Thank you!

 

DBLOTII

+! = thanks - good info

 

Dave,

While we're on the subject, let's say that the engine isn't being pushed at all - let's say kept under 2500 or even 3000 (the "no knock zone" as I'm calling it). Do you have any quantitative data for expected efficiency of 87 vs 89/91/93?

Thanks!

Jeff

 

Not to re-ignite the bonfire, but if you re-read my posts carefully, I think I made most of these points... albeit in a not-so-friendly manner. I've also been curious, with modern adaptive algorythmns, and under steady state conditions, will the system rewrite the timing map and KEEP the timing retarded below the detectable knock limit until conditions change? Asked differently, does a modern engine control system have to continually allow intermittent boderline knock in order to control it? Thanks for this.

 

Knock is roughly just as likely at low speed as high engine speed. It is mainly dependent on the load (if the engine had a throttle that would be throttle position). To answer your question, if you are running at light load, at any engine speed, away from the knock limit, the fuel Octane has no effect on engine efficiency. Also high octane has pretty much the same energy content as regular, assuming both have the same percentage of alchohol.

Gasoline properties vary quite a bit from month to month and from region to region, even within North America. About the only barely significant difference between high and low Octane is the vapor pressure (data I saw about 10 years ago), that is the tendency for the fuel to evaporate. Regular tends to be ever so slightly more volatile, but not so much so that you should notice a difference in cold start performance. This has no measureable effect on a normal running engine.

Dave

 

My understanding is that for modern ECU's, knocking does not rewrite any of the timing maps. The base timing maps are always there. There are many methods of dealing with different Octane fuel. In some cases, the ECU figures that the Octane is low, and switches to the low-Octane timing map, but it regularly checks to see if it should stay with this map or go back to the normal timing map. Other systems, simply keep the engine running at bordrline knock when the load is high. I don't know what the Mini uses.

Dave

 

I think you all need to take your gold chains off and cool down - getting hot under the collar isn't the problem - it's the gas prices which are skyrocketing and causing this conversation.

 

Hi Dave,

I'm confused. It has always been my understanding that RPM is a pretty direct indicator of how hard the engine is working. How is "load" any different from that? Would you please clarify?

Jeff

 

Actually, this is one of those conversations that happen cause "guys are guys" and we like to tech-out. If gas were $1 a gallon it wouldn't change what we are interested in. Personally, I find it fascinating how and why things work the way they do ... but I also like ballroom dancing - go figure.

 

Can someone explain to me in very simple terms what makes the MC engine different from my old Civic's engine, so it requires premium gas and the Civic didn't? I understand that the MCS has the turbo and why that would need a higher octane fuel. Kind of. But I don't understand why the MC needs it, and when people ask me why I use premium gas, I just sort of stare at them blankly. I'd like to have an answer.

 

Well, there's a big difference between cruising along at 2500 RPM and 50 mph in top gear versus being at 2500 RPM in a lower gear and punching the gas to pass someone. In fact, "lugging the engine" (trying to accelerate from too low of an engine RPM) puts a LOT more load on the engine than higher steady-state RPM. The reason for the increased load is that applying the throttle at a low RPM dumps a lot of gas into the cylinders, but the engine isn't making enough torque to accelerate quickly, so the extra fuel causes the dynamic pressure inside the combustion chamber to spike up.

The biggest difference is that the Cooper likely has a much higher static compression ratio than your old Civic. The Cooper's compression ratio is about 11-to-1, whereas my old Civic (a 1995 DX) had a compression ratio closer to 9-to-1. The higher compression ratio requires a higher grade of gasoline to avoid spontaneous combustion when the air/fuel mixture is pressurized in the cylinder.

 

Thanks Dave. That was just the info I was looking for.

 

Engine speed and engine load are the 2 basic independent variables in how you can operate your engine, especially if you have a manual transmission. At any engine rpm you can vary how much fuel and air the engine consumes by changing the accelerator pedal position. You can vary between no net torque (no acceleration or the transmission in neutral) or full torque at any engine speed.

An automatic wil not allow you to run at low rpm high torque, because it will downshift for you and raise the rpm. If low rpm high load gives you enough acceleration at a particular instant in time, then that is the most efficient way to accelerate. So for maximum economy, you want to be in the highest numerical gear that gives you enough acceleration (for say the next 10 seconds), wiithout lugging the engine. Automatics can't know what you want for the immediate future, so they assume that you want a lot of power when you push hard on the gas pedal and therefore move the engine to high rpm where more power is available. Engine power (not torque) is the ultimate determinant of how fast a car will accelerate at any given instant. I know that many car magazines suggest the opposite is true, but the equation of motion for any vehicle is:
Accel is proportinal to Engine power/(Vehicle mass x Vehicle speed)

Don't confuse engine torque with torque at the wheels.

Dave

 

i have a first generation mini and have used regular gas for over two years. I have experienced no pinging, engine trouble, blown rings etc. The service tech at Mini has run his Mini on regular for 3 years. Worst case the sensor goes off, have it reset at Mini and then use premium.

Over this past winter Mini dealers were experiencing unusually large amounts of cold weather start complaints...... Mini of America had the dealers analyze the gasoline and pull fuel tanks..... the results showed that the premium gas being sold which was supposed to have up to 12% ethanol contained between 22 and 32% ethanol..... thus the use of regular gas for me.

 

Dave,

THANK YOU! It may take me a bit to properly savvy all that and I really appreciate your detailed response.

Jeff

 

A MINI or MCS?

How much ethanol should be in regular (87), plus (89), premium (91), or premium + (93)?

 

If you go to the "Top Tier Gas" website (www.toptiergas.com), their requirements for "top tier" status require that the gasoline must contain at least 8% and no more than 10% ethanol, at all of their retail stations and in all grades of their fuel.

Of course, that's just for "top tier" retailers - I don't know what the overarching federal guidelines are regarding ethanol.

 

I'm trying a tank of regular Citgo. I drove 300+ miles today down and back to NY on the Taconic (rolling hills). I was trying for economy mind you, but the OBC is reading 53 mpg!