I have a 2006 mini s R52 which gets 28.3 mpg in the summer and 27.? in the winter

I had a tune up with spark plugs and new filters 10 months ago and less than 10k miles ago. For a short time it upped my gas mileage to 29.?

In early october my driving changed and my gas mileage when up slightly.
Then I got and engine warning light and the shop told me that I needed new Manifold Air Pressure Sensors.

I bought them and my gas mileage immediately dropped to 26.1-26.4
this hurt my feelings so I called the shop to let them know my suspicions but with the new driving (more in town) and extra cold winter I gave it several tanks of varying driving including heavy hwy tanks before taking it back never getting more than 27mpg per tank.

They had no idea, said that I needed new plugs but could not explain why they would be dirty after 10 months when they should last 3 years and put in fuel injector cleaner.

Half a tank later, with weather running from 0-30 degrees and very short hop driving, on top of the 30 mile trip back from the shop, my car is telling me the average gas mileage is for this tank is 16.4

I have been driving cautiously, avoiding quick starts and taking my foot off of the gas when I see a stop coming up. Much more so than I was before this whole thing started.

Any input would be helpful. Thanks!

 

I'm not sure this will help, splat but I've notice that my 2013 get much worst gas milage during the winter months. I went from averaging about 34 mpg to between 27-30 mpg. Spring is right around the corner and hopefully better milage as well.

 

Lots of things combine to make mpg worse in the winter...most folks DO loose a couple MPG in the winter....
Such basic, unchangeable things as your RUBBER tires being stiffer, causing more rolling resistance, the oils and lube being thicker when cold, the engine idling more and at a higher rpm to warm up, seasonal changes in fuel mixes (using lighter compounds to raise vapor pressure, to make cold weather starting, but less BTU's per gallon)....heck I find I accelerate FASTER in the winter...my car makes MORE POWER...
I would keep an eye on it, but I bet most of your MPG comes back with warmer wether and better fuels...if it does not, then it might be time to look deeper...at things like aging 02 sensors, a dragging brake, or even a sticky thermostat!

 

Here in CT, I've gone from 37.2ish down to 32.0 or less.

 

It has never lost so much mileage in the winter before but perhaps the mixture is different or not quite up to the colder than average weather. The car has been a bit harder to start than usual.

It's especially annoying as i went on a road trip right before everything started to go weird and got 500 miles on one tank. But then i guess that was the bad map sensor

new summer gas should hit soon, maybe i just need to be patient
Thank you for your advice

 

A friend put forth that this sounds like it could be excessive carbon buildup.
My model is one that has the extended warranty for the O2 sensor.

that would be an awesome answer because outside the hour drive to the dealership the repair is free.

hopehopehopehope

 

Carbon issues are pretty rare on an gen1.....a bottle of techron or bg44k and a couple "spirited" drives would clean it up....driven very lightly....possible.
A bad o2 sensor WILL TURN ON A LIGHT.... The computer is modern enough that it watches the speed of the voltage change on them to determine if it is working right....SOME GEN1 cars DO have an extra warrenty on the o2 sensors.....think they were a segment of 2004/05 production BY DATE (some some 06 production might be covered).....you might ask for future reference to be sure...

 

Why is the fuel economy of an automobile worse in the winter than in the summer?
http://www.scientificamerican.com/ar...uel-economy-o/



Apr 19, 2004


Harold Schock, professor of mechanical engineering and the director of the Automotive Research Experiment Station at Michigan State University, explains.
Every new car sold in the U.S. has a manufacturer-provided fuel economy sticker describing mileage for urban and highway driving. This fuel economy is measured by operating the vehicle on a chassis dynamometer using a repeatable driving schedule. A chassis dynamometer acts like a vehicle treadmill, allowing a drivetrain to operate while the vehicle is stationary. Before these tests, a car is "cold soaked" for 12 hours at temperatures between 68 and 86 Fahrenheit. This treatment, together with the specified driving schedules set by the Environmental Protection Agency (EPA), provide a standard basis for comparing one vehicle to another. Urban driving is simulated using specifically prescribed accelerations, decelerations and periods of idling typical of the stop-and-go driving expected in cities. The highway schedule contains fewer accelerations and decelerations and speeds typical of freeway driving. During these experiments technicians measure both emission levels and fuel economy. Emission levels must meet standards set by the EPA, whereas the Department of Transportation sets the corporate average fuel economy (CAFE) standards, which are reported in miles per gallon (MPG). The measured fuel economy is multiplied by a scale factor to account for the differences between laboratory measurements and real driving conditions. For example, the urban mileage on the sticker of a new automobile sold in the U.S. is actually 10 percent lower than the laboratory measured value and the highway mileage listed is 22 percent less than the laboratory value.


In contrast to the precisely controlled experiments described above, a typical driver does not operate under ideal conditions. The actual mileage (MPG) that a given vehicle will deliver depends on three general factors: driving style, road conditions and the additional energy consumed when the outside temperature decreases. For example, aggressive drivers will obtain fuel economy values that are lower than those achieved by more cautious drivers. Vehicle fuel economy can be severely diminished if additional work is required to move a vehicle through snow or water on a highway or if excessive weight is stored in the car. Tire slippage can occur on wet or icy highways, which wastes energy and decreases fuel economy. In addition, in cold climates many people bring the interiors to a comfortable temperature before driving and keep their engines idling during prolonged waiting periods to maintain that temperature. Excessive stop and go driving in heavy traffic, use of heater motors, windshield wipers and defrosting devices all cause additional fuel consumption and reduce fuel economy. It is difficult to estimate exact percentages of fuel economy reduction for these factors as they vary considerably between drivers and different road conditions, but any time a car is warming up or not moving with the engine running, the fuel economy is 0 MPG.


Auto components such as electric motors, engines, transmissions and tires consume more energy at low temperatures, especially during startup. The viscosity of the oil and other fluids increases with decreasing temperature, which means that more work and more fuel is required to overcome friction in the engine, transmission and other drivetrain components. If the outside temperature is significantly below the ambient temperature at which the EPA prescribed tests were conducted and trips are short, the engine's coolant system never reaches normal operating temperature and more fuel is utilized. Additionally, the amount of drag between tires and the road is about 20 percent greater at 0 degrees F than it is at 80 degrees F. Operating tires at lower than recommended operating pressure further degrades a vehicle's fuel economy, but this is also a problem in warm weather.

Finally, a vehicle's aerodynamic drag is proportional to air density. On a 70-degree-F day, the density of the air is 16 percent lower than on a day with temperatures around 0 degrees F. Although this makes little difference in urban driving, it could account for a highway mileage per gallon reduction of 7 percent on the colder day (including a 1.5 percent allowance for improvement in fuel efficiency at the higher engine load).

Considering all these factors, the fuel economy during urban trips of less than 10 minutes, in cold weather with snowy road conditions can easily be 50 percent lower than operation of the same vehicle in warm weather with dry roads.

 

50% Wow! normally my mileage drops by less than 1 mpg in the winter but a drop from 28.3 - 16.3 is closing in on 50%. Though I never let the car warm up I am often late and that is not an option. I will see what happens when I go out of town today that should perk up the average.

 

Also, did you switch to winter tires? If they are different diameter this can affect your measured mpg.

 

My in city MPG went from about 27mpg to around 20mpg. Highway 36mpg to about 30mpg. From my experience this is very normal. My R53 would average 27 across (city and highway) in the summer time and 19 in the winter. I live in eastern Iowa and we get very cold winters. Usually quite a few weeks with sub-zero temps.

 

So, i pop into my car today and i start flipping through the computer readouts. I discover that not only is my mpg super low but my average speed is also only 15.
I usually reset my trip meter when i get gas, about half a tank ago, i flip from the clock to the trip meter... 25 miles.
then i remember that the other day it was -8 and when i tried to start the car. It had a bit of a problem starting and the electronics blinked, erasing all of the computer readouts
after taking the extra scenic extra hwy route to and from my friends house my mpg is back up to 25 and i feel very sheepish


...unless someone knows why spark plugs would look iffy after only 10 months and what kind to buy to replace them, thinking i might do the wires too. Apparently the how to video is less than 15 minutes so how hard can it be?