I'm 2.5 months into ownership of a pre-owned 2006 MCS. I bought it with about 21K miles on it. Based on comments from MCS owners, I think my fuel economy may indicate a problem.

I've read many many posts about this topic on NAM, so I'm familiar with the role that driving style can play. I drove pretty spiritedly with my first tank and got 17.3 city. Since then, I've driven more or less sedately in town to maximize my MPG. Perhaps not always like a grandma, but definitely with an eye on fuel economy (trying to shift before 3k).

I've been keeping a mileage log relying on real data (not OBC calculations). I've always used 92 or 93 octane. I've also gone out of my way to run a few tanks of top tier gasoline through it, and that doesn't seem to help or hurt.

Here's why I'm concerned - my MPG info follows:

City (over the course of about 600 miles): 19.4 mpg @ about 22 avg mph. My typical commute is about 12 minutes over residential streets. I rarely, if ever get on the freeway during a typical week. My low was 17.3 mpg and my high was 19.3 mpg.

Highway (over the course of 1900 miles): 25.87 @ about 66 avg mph. Low was 22.6 and high was 30.1. Interestingly, my car seems to do better on Iowa and Kansas gas than Illinois gas (perhaps by 2-4 MPG on the highway), despite the slightly lower octane (93 in Illinois, 91 or 92 in Iowa/Kansas).

Based on what I've read here, I think I should be getting 24/32 instead of 19/26.

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Which brings me to my question:
What are the possible culprits for fuel economy problems (putting aside the possibility of driving style)?

I know of two possibilities:
1) low tire pressure: I'm running about 34-35 PSI front and back now - doesn't seem to be the problem (have factory 16" wheels)
2) dirty air filter: This could be an issue- filter looked sort of dark on the bottom when I popped it out last week. I vacuumed it and returned it to the stock box. That didn't seem to help. I'm replacing it with a DDM intake this month, so I hope to eliminate this as a source of the problem. Could this explain a 4-6 MPG reduction by itself?

What other causes could be at issue here?

For now the car has no performance upgrades, but I plan to do the 15% pulley and the DDM intake this month, and I think I should get this looked at by the dealer while the car is in essentially "stock" condition because of warranty.

Or should I just accept the fact that my car is going to get 19/26 and stop worrying about it?

 

Your gas mileage is subpar if indeed you drive the car casually. If you are getting on it fairly often, then those numbers are about right. The city driving figure contains too many variables to come to a distinct conclusion [as in something the dealer can't easily deny]. However, I'd say fill the tank up to the very top nearby an expressway. Immediately get on the highway and set the cruise conrol at 65mph, the longer you drive the more accurate the results will be. Using this auto search forum forumdig.com you can go over all the variables that can contribute to poor gas mileage, some of which you mentioned, tire pressure, suspension/alignment issues, etc.

 

Over the course of owning 3 MINIs, I have come to the following conclusions: 1) cold weather will play hell with your MPG. 2) Nothing you say or do will matter to the dealer.
In reality, cold temps will cause the computer to adjust fuel delivery to your detriment. Live with it. Anything else will give you ulcers. I typically lose 5 MPG during the cold weather months and have learned to live with it, rather than frequent trips to the dealer, who can't or won't figure it out. Hope this helps.

 

What would be a reasonable expectation for a MPG at 65mph?

thanks,
bonmot

 

I was slightly surprised at the reduced MPG recently, too. With all city driving in my 07 MCS, I was getting 27/28, then when Winter hit, it suddenly dropped to 23. By driving "softly" I was able to get 26. I figured the ethanol they add here in NM is affecting it. Plus, stations here only offer 91 octane for premium.

[Yeah, I know mine's a 2nd gen, but I'm posting to comment on the affect of cold weather.]

gl

 

It was pretty temperate here during late october and early november. My MPG wasn't great then either. Are you saying it's only optimal in late spring/summer/early fall?

I hadn't considered that my dealer may give me trouble about this issue under warranty. That's discouraging. Most of the threads on low MPG here end in one of two ways
1) people saying "it's your driving style"
2) people saying "take it to the dealer. Something's not right."

I just assumed they would probably figure it out and not charge me. Doh!

thanks for your thoughts...

 

One big culprit is the elevated levels of ethanol that go in the gas for winter, like greylight said. Have you checked your plugs?
And, yes, a dirty air filter has a significant effect on mpg. Replace soonest, or upgrade to K&N or somesuch.
(I know, I know. Everybody has the "must have" air filtration system, but at least K&N is better than stock or paper aftermarket.) Sheesh, gimme some slack here.

 

As skip and greylight point out, the winter blend fuels will reduce your MPG regardless of the ambient temps. I imagine the distributors in your area had begun delivering these fuel blends locally by late October. Then, when it does actually get cold, you have the added effect of the computer adjusting it to your disadvantage, as NMgokart notes.

I also notice 3-5 less MPG, on average, over the winter with the exact same driving habits.

 

If I drive behind people doing 45 in a 55 or just below 55, I get 22-24 MPG locally. On the highway strictly 65+ I can get 28. I have seen 30.1 on a gentle drive after a fill up, but as soon as you goose it once or twice or even idle for a couple of minutes it will drop to 25 or less.

 

Thanks for all of the info so far. I have heard about winter gas being different, but I didn't realize it could make that kind of impact. In my last car (Accord V6) I don't think I noticed that kind of predictable change in the winter, but I certainly wasn't paying close attention.

I would guess that dozens of people on NAM (if not well over 100) bought their cars between October and March in northern states. I would think that each of them would have been concerned at their fuel economy if it was similar to mine. Or maybe people here aren't checking their fuel economy regularly.

I haven't checked my plugs. What should I look for? Proper gap? Carbon fouling? I don't have a lot of DIY experience of that sort.

It seems to me that now is the time for me to have the dealer look at my car because it's still stock. Are you all recommending that I forget taking it in to the dealer and wait till spring and hope that the gas changeover fixes the problem? It becomes a much stickier situation then (I can imagine a dealer saying "sorry, your aftermarket upgrades introduce to many variables that could affect MPG. We can't help you.")

Thanks again for all of your ideas so far. It's been educational.

 

I lose 2-3 mpg in cold weather,and I wait 'til the tach drops below 1000 rpm and the temp gauge is @ 1/8" above the bottom of the gauge before I motor.I was always told to warm up vehicles before driving,maybe that's where some of my lower gas mileage is going! Also,I drive 5 miles to work on city streets,with @ 15 traffic lights to deal with.So it's good to get out on the freeway often and clean things out!

 

What kind of mileage do you get with your commute, since it seems similar to mine - no highway?

 

I also have a short commute (5 miles) with ~ 7 lights. A tank that is 80% commute, and 20% highway (75mph) I'm consistently getting 19-20mpg. It is down a bit this winter (in NJ). Around town, I will drive with some "spirit", but nothing too aggressive. I only pay attention to the mileage I calculate from the odometer and what I put in the tank. too may variables to trust the OBC.

 

My car is similar. My lifetime average is just a hair over 22 MPG (which is about what I average in mixed driving) and the most I ever got was 30.67 when I drove on a 2.5 hour (each way) trip staying within 5 MPH of the speed limit with sparse traffic.

A funny thing though (or not so funny as it makes sense that the engine just loosens up). I started keeping track when my car had 13,000 miles. Now, it has 37,000 and I get about 2 MPG avg better than it did when I started. I graph it and it is clearly visible on the graph, even moreso when I plot a trendline on the graph.

 

Ok, so you live in San Diego County in California and you are letting your car warm up?

You do not need to let your car warm up unless it will not operate until doing so. When living in upstate NY, one of the coldest places in the U.S., we used to let the car warm up because otherwise the transmission would not work very well. Here in more temperate Connecticut, but still quite cold compared to California (even mountainous CA) it is not necessary to let the car warm at all. Just get in, turn the key and go. Don't sprint out of the driveway, but driving it will warm it more quickly than letting it idle.

Warming up the car is a legacy of carbueretion. Modern fuel injected vehicles do not need to be warmed up before driving. This is made easier in our vehicles by the use of synthetic oils (typically 5w-30 in the Mini), which have signficantly improved lower temperature flow properties compared with the typical 10w40 oils used in most domestic cars.

Don't warm the car up unless it is 20 below zero. To do otherwise is wasteful.

 

I am shocked at the low mileage figures people are getting. I do not drive like a grandma, but in the summer I routinely get 32 mpg in a daily commute of 20 minutes local driving and 20 minutes @ 70+mph highway each way.

I have been really disappointed when my mileage went from this level to 28 mpg, and when we had temps in the low teens recently saw mileage figures get down to 26 mpg. Then I started looking for reasons and stumbled across this thread. I too would be looking for answers if I was gettign 19 mpg. Heck, I'd be embarrassed that some SUVs and minivans are getting better mileage!

At 60k miles, I am thinking an air filter change and new spark plugs are in order. I will do those next weekend and see if there is any improvement. Changing my oil made a minor difference.

 

It makes me feel a little better about my answer-seeking to read your comments. I've read too many threads here where people have questioned their MPG only to have people say things like "a MINI isn't an economy car." That's true, but it ought to be significantly more economical than my 3.0 liter V6 accord coupe automatic was. Around the city, they have been quite similar, with the Mini actually doing worse by 1 MPG or so.

 

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