Help- City MPG dropped from 20 to 15

[waterbuck1]

I have a new 2009 Mazda 6 4 cyl, which I purchased 8 weeks ago.

At 1400 miles, it has suffered had a big decline in mileage and i don't know what to tell the dealer to look for, because they either just can't believe me when I say that the car ever got 20pmg in town, or they seem to think that a 25% loss of gas mileage is kind of normal for the first month of ownership.


When I first got it, it did 20-21 in town, 28 on the highway, sometimes 29-30 on highway. That's the EPA rated mileage. I dont run the tach over 2200 rpm except in emergencies.

Then 4 weeks ago, I ran over a curb (low velocity but it was a high 8-inch curb at 5 mph. It made a big hard bump and shredded the left rear tire, which had to be replaced; so it was a very hard bump to the left rear wheel)

After that it got 15 in town, 24 on highway.The other thing I noticed was that the car seemed to slow down quickly when I took my foot off the gas.

I confirmed that my mileage estimation was correct twice through driving 100 miles and refilling the tank. And the trip meter agreed: 15-16 mpg in-town for a 4-cylinder engine.

So I took it to the dealer where I bought it, MedCenter Mazda in Pelham, Alabama.

They had it for 4 days.
They said they looked at the brakes and found nothing wrong, and they ran some kind of electronic diagnostic suite and found nothing wrong.

They said they drove it twice for about 10 miles, roughly half highway, half city and got 18.75 mpg. They didn't literally say "that's normal for this car", but strongly hinted that this was pretty much what would be expected.

Actually, for half-city, half-highway, 18.75 mpg is nothing like what it used to get, and not what the EPA says it should get.

I don't really know what to do. ONe person suggested I ask them to visually inspect the bearings on the wheel that got bumped. Maybe a bearing was damaged.

The car doesn't seem to make any screeching or funny noises, but I'm just baffled. Is 15mpg just normal for this 4-cylinder car? Why would the mileage drop so much?

Could I have a newly defective odometer?

Thanks for any suggestions.
Waterbuck

 

[_MSprotegy]

that deffinatly does NOT sound normal for any 4 cyl vehicle. hell my speed 6 gets like 17-18 mpg city and 22-23 highway.

 

[waterbuck1]

My service dept seems ambivalent on whether to take this seriously

I agree with you. The car got 20 mpg in town for the first 5 weeks of ownership, pretty much what it's rated to get by the EPA. Then, after I ran over a curb and had a new tire put on, it got 15 and seems to lose speed and "drag' when I take my foot off the gas, very quickly.

My first problem is that the Mazda Dealer Service Department doesn't seem to convinced there is a problem to fix.

They looked at the brakes, which are fine. Electronic diagnostics are fine.
The dealer staff drove it 10 miles, twice. They got 18 mpg driving half highway, half city. That confirms the problem in my view, because it's far below the EPA rating of 21/29, and 25% below the 23-24 I was getting in half-highway/half-city driving in the first month of ownership.

The problem is the dealer service department is telling me the car is just fine. They don't seem to know what to do and they are strongly encouraging me to see 15 mpg (city) as normal for a 4-cylinder Mazda 6, even if it used to get 20-21 mpg in city conditions.

If anyone can suggest things they should check, tell me...

Could I have crunched a wheel bearing, bent an axle, damaged a coupling? Could it be a bad odometer?

They did mention that they have an "engineer" who comes over from Atlanta once a month, so perhaps I can ask for the "engineer to look at it.

My biggest challenge is that I think they feel they have done all they can.

waterbuck

 

[Super Shredder]

When I first got it, it did 20-21 in town, 28 on the highway, sometimes 29-30 on highway. That's the EPA rated mileage. I dont run the tach over 2200 rpm except in emergencies.

most NA cars run most efficiently at 3000rpm. and your new car was probably designed to have pep at the same time as making good gas mileage. also. change your oil. did you at 500 miles? do it. then do it again at 3000. at the 3000 you can switch to synthetic and then do it every 5000miles. this will help big time. get an air intake. guarenteed mpg. i'm making an average of 26mpg and i live in the mountains and drive about 100miles every day. maybe 30% highway. i also have a speed6.

 

[bova80]

check your tire pressure.

 

[tunersteve]

Moved to proper section. Please note there is a specific section for the 09+ 6 models now as well.

 

[GoFast]

have you checked you alignment? It definitely has something to do with the impact. bearing, alignment, tires, etc....

 

[Blendercloud]

These guys all said it best. Check the wheel bearing, alignment, tire pressure, change your oil, also check that the replaced tire is identical to the others. It seems to me that it is either that tire/wheel hub assembly or that your curb incident coincidently fell in line with the break-in of the engine. Either way, Mazda owes you some sort of explanation or solution. Request an appointment with the engineer.

 

[waterbuck1]

update on the low-mileage car

The car was left at the dealer for the last week.

The service manager states he ran electronic diagnostics on it, did alignment, checked the speedometer, changed the oil and looked closely at the wheel (and brake) I had bumped and could find no problem. He said it didn't make any noises to suggest a bearing damaged.

He drove it for 10 miles, twice, and obtained 18.7 mpg in "half town-half highway" driving.

He talked to Mazda engineers, who suggested that possibly the ethanol content of local gasoline is the issue, but he didn't seem too convinced.

I got the car back today and he told me to call him when I reach half a tank to report the number of miles traveled. I drove about half-highway/half-town the 12 miles to get home and the average fuel consumption on the trip meter is 16 mpg, for a 4-cylinder Mazda6 rated for 20 in town, 29 in the highway.

I'm not really sure what to pursue, but he did hint that a Mazda engineer comes out to the dealer twice a month, so I could try to ask for them to have that engineer look at the car then.

waterbuck

So it remains pretty mysterious and if anyone has any ideas, please do post them.

 

[Blendercloud]

It is true that the 10% ethanol that most larger municipalities require in their unleaded fuel does reduce the fuel economy. However, if you were using the same fuel before it doesn't really add up.

I have a friend who bought a new Chevy truck with the gas 502. It was EPA rated at 10mpg and he could never get more than 6mpg out of it. After 4,000 miles Chevrolet took the truck back and gave him a new one. Just keep everything documented (mileage, oil changes, fuel economy per tank for every tank) and keep talking to the service manager. Don't let them forget about your problem.

 

[Smooth1]

I get 23 mpg city and 30 hwy in my 6. Your main problem is that there isn't anything obvious. No noises and no check engine light. Without the check engine light there's really nothing to trace....no codes. Don't get cheap fuel. I only use Shell in mine.

 

[plv]

I'm sure the dealership has already tried this, but you could jack up the car yourself and see if the wheels spin freely or not. Also maybe check for gas leaks when the fuel system is pressurized (while the car is running).

 

[speed1585]

I would think its a problem with your new tire, rim, balanced properly? and allignment.

Did you get an alignment after you hit the curb?