in the last week or so my gas mileage has gone downhill. (from average 30 MPG to 23-25). i also notice a decrease in performance and pickup at lower RPMs. (1,000-4,000). only thing ive done different is change tires. they are all season potenzas. i also wonder if its the winter gas blend changes causing the drop. does anybody know when stations make/made the change to winter gas?

BTW i have a 2007 MCS with an alta CIA, i would think the cold weather would increase performance.

 

I changed over to all season Potenzas from my OEM tires but never saw a decrease in gas mileage. What pressure are you running?

 

good question. never checked it, just assumed they filled them correctly. they "look" ok.

its weird, the engine seems much less responsive. the get up and go is gone.

 

Definitely check what the filled them to. You might be surprised. Although it sounds like your issue might be more engine related.

 

It definately sounds engine related. I am no mechanic but I would guess that the engine is running in a rich condition. Common causes could be a bad thermostat or perhaps an O2 sensor. I am surprised that the engine warning light has not come on. I'd visit the dealer and they can handle it.

 

A 25% drop in MPG is pretty drastic. My MPG usually goes down 5-10% in winter. This sounds like an issue that needs to be checked out at the dealer.

 

yea, that is unusual. You may want to check your MAF to make sure it is clean too. Easy to check before going to the dealer.

 

i made an apt for tomorrow at 12. we'll see what happens.

 

tire pressure was ok. checked oil and noticed a gasoline smell. but all my cars have had that smell. what should oil smell like? it always smell like gasoline...no?

 

Could it be bad gas?

 

ive filled up a few times from different stations and its still happening.

 

We just motor'd up to New York (Son returned from Iraq! ) I noticed a big drop in MPG. It was summer last time and we avg'd about 38, this time we got 32. The two differences were new tires (Nexen 3000 on 18s) and it was winter. Here in AL the MPG seems to be going back up. We'll see.

 

Well.. better than mine.
I continuously get 15-16 mpg on my MCS.
Filter's clean (car has only like 1200 miles on it), I check tire pressure every month, no performance mods, only city driving.
I think the wife has a lead foot. She doesn't like the turbo kicking in at around 2k rpm and she's still not used to it. She gives it more gas before the 2K and it bucks on her (she's driving an auto).
Still... I don't see how she gets that low of a mpg even with that style of driving.

 

That seems awfully low. But I have driven in Honolulu traffic. Spending a lot of time idling in traffic could do it??

 

True... Read a few weeks ago in the newspaper that Honolulu has the worst traffic congestion in the country (more than #2 - LA).

 

Try this sometime: reset your mpg indicator and drive for a couple of miles, very gently, to try to get a high cumulative mpg. Then just sit with the engine idling, as though you're at a red light. You can see the average mpg drop right before your eyes. City driving is terrible on mileage, not just because of engine inefficiency at low speeds and more fuel needed accelerating from stops. It is also impacted by consuming fuel without adding any miles to the numerator of the calculation (mpg), that is, while stopped at red lights.

This is the reason that the European-build MINIs have the automatic start/stop feature that shuts off the engine and restarts it when sitting at traffic lights.

 

I got one tank of "bad gas" early in the summer that had my normal mpgs in the 30s instead of the 40s. Four or five tanks later things got better...been back up in the 40s for awhile now.

 

I've tried resetting the indicator before.
Goes right back to 16.

 

gmhl10,

I didn't mean to suggest that resetting the indicator would change anything in regard to gas mileage. I meant that it graphically indicates the impossibility of doing anything much to improve gas mileage when in heavy traffic or city driving. Any car that spends more time sitting than moving will get much worse mileage...unless the engine is turned off when stationary.

 

Very true....mpgs improve drastically w/ a warmed up engine. I have a friend who has a very short commute and his mpg generally is far less than mine...but I have a longer commute.

If it were possible to erase the data from the engine warm-up period...OBC readings would be (on my car anyway) in the mid to high 40s. But since half of my commute is spent w/ the engine still getting to optimal temps, the numbers initially plummet and then rise.

 

I've only had mine a few weeks, but it is frustrating not being able to tell when the engine is fully warm. With all of their sophisticated electronics, I'm surprised the MINIs don't have any indication of engine temperature (other than a warning light when they are too hot).

 

What would you do differently if you did know?

I've got a Scangauge in ours which can be set to show the coolant temperature (and currently are).

 

I like to know the engine temperature, because in the winter I like to wait until the engine is warm to turn on the fan for the heat.

 

Forget the indicator. How many miles do you get between fill ups? My 07 MCS does 450 miles comfortably between tanks.

 

I get 6 to 8 mpg going up my driveway. It is a long switchback climbing about 400 ft. in altitude in 1st gear at about 15 mph. On a 20 mile trip from town, this can drop the average a couple of mpg. Arrive at the bottom of the drive with an average at about 30 mpg then watch it drop to about 27 as I climb. So, how and where you drive will have a significant effect.

If you only do city driving, take it out on a freeway or highway sometime and blow the cobwebs out.