I'm residing in Montana this winter and it's the first time I've driven my MINI Cooper S ('06) in weather between zero and 30 degrees Fahrenheit. Since the temperatures have dropped to these levels so far, I have noticed a huge decrease in MPG. Does anyone know if ambient temperature that low does commonly kill your MPG on a car? Is there anything to improve it?

Some stats and info:
I've been getting 19mpg city driving. My driving habit is to be very easy on the accelerator and not to accelerate hard. This is all driving with a very light foot to try and keep my mpg higher.

Prior to this winter, I was getting at least 24mpg if not 28+mpg city driving in the summer.
One of the things I'm worried about is that I installed a CAI in early November...about the same time that I lost my higher MPG. I also had an SES light come on with a report of fuel vapor escaping (or something like that), but that was due to the fuel cap not being on properly (or so I thought!).

Hopefully I can figure something out because it's really sad seeing only 250 miles per tank of gas!

EDIT: Since posting this I found this thread that seems to suggest cold weather and MINIs don't get along!
https://www.northamericanmotoring.co...d.php?t=124953

 

Sorry, aorr, but it's perfecty normal. When it's that cold, the air is denser and there's more wind resistance. The oil in your engine and transmission are also lots thicker, so it takes more hp to turn the gears and move the car. The engine oil will eventually heat up to normal, but the tranny oil takes a lot longer to reach normal operating temp. Even the grease in your wheel bearings offers more resistance. Here on the east coast (maybe where you are, too) our gasoline is reformulated (more additives to burn cleaner) and that takes away some mpg.

The only things you can do is to be sure the air pressure in your tires is right (lower pressure = lower mpg), and keep your car in a heated garage. And hope for an early spring

 

I question the dense air hypothesis above...the little woman's 06 cooper gets the same milage (30.5 mixed highway/ city) in the winter as it does in nicer weather. Her 02 cooper never really changed either (29.5 mpg most of the time). This is upstate NY and while we've only had a couple of cold weeks here it's been a couple of tank fulls worth of cold, snowy driving. 19 mpg with a light foot sounds terrible for one of these little things. My Manvan, by comparison, gets the same 24 mpg it always does in the same sort of mixed driving. I'd start looking at O2 sensors...

 

doesnt the cooper s have higher compression than a cooper ? could that be the cause

I know that I have seen a 5% decrease in MPG since winter kicked in 0 - 20 degrees then the last week it shot up to 40 and my MPG came rushing back, this is in an 03 Cooper <non-s>

 

I have always noticed a 3 mpg loss or so in the winter - most of this is because of the winter fuel mix (uses more ethanol, I think). Many folks have reported this issue during the winter, completely normal. Just wait until you are running an ethanol mix year round and you can have decreased mpg all year! Temperature does also play a role in decreased mpg.

 

#1 Check tire pressures.
#2 Switch to mid grade gas for cold weather.
#3 Let the MINI warm up some before driving.

I'd bet your tires are low on air.

 

Thanks for the replies!
Regardless of what might be causing it I'm stuck with it until I head to the nearest dealer this summer. Salt lake is a 8.5 hour drive. Would be a long trip just to find out it wasn't the O2 sensors. Also waiting until summer will let me drive in normal temps again! :-) I want to say that I see the MPG come back up when we have warm days here (in the very low 40s) but that might just be my imagination. I like the idea of the fuel additives for winter. That makes a lot of sense for the decrease.

Yep, I just hope summer comes early this year!
Thanks again!
-Andy

 

Definitely check the tire pressures. Its amazing how many people of all makes of vehicles drive around with very low tires during the winter. They probably rarely check the pressure and had them filled in the summer and then wonder why their tires look low in 20 degree weather.

 

The Cooper actually has a higher *static* compression ratio than the 'S', but with the forced induction in the 'S', the *dynamic* compression ratio is a bit higher.

I just finished a 3200-mile road trip, and the temperatures varied from 17°F to 75°F. I didn't notice a big change in fuel economy as the temperature changed, but most of the trip was on the interstate. Regardless, I've *never* gotten 19MPG over the course of a full tank. "Low" for me is 24-25MPG, even with purely in-city driving.

 

Does Montana use "oxegenated fuel" in the winter? We do here and it does effect mileage. We also run 10% ethanol which also effects it. Together they eliminate the need to add fuel line conditioner for moisture. So no more frozen gas lines here.
Also if you're warming up the car before driving that would also effect your overall mileage. My truck goes from 14mpg in the summer to 12 in the winter for all these reasons.

 

Cooper S has 8:1 compression ratio and the Standard has 10:1 ratio. S compensates with compression by supercharging. My 03 S gets same MPG all year round. Have yet to change O2s with 51,500 miles. Mostly Solo and PDX/Time Trials and Road Rally with SCCA. Check tune, plugs and O2s do not last 100,000 miles as manual and dealers say to change. You do not need to warm car if you use the 5w/30 oil recommended. Just do not drive spiritedly until gauge is almost to normal. Trans fluid same, not lifetime as dealers suggest, should be changed in regular intervals also.