To clarify a few things here.

You are absolutely right about the "sweet spot". However, maintaining 35mph in 5th gear does yield much better gas mileage vs. 4th gear, verified by ScanGauge II. Lucky for you with a 2007 Mazda3 which comes with free trip computer (I read about this somewhere), so you can test it out. I don't know about the 2.0L engine, the 2.3L turns at 1500rpm in this situation and has plenty of torque to maintain the speed while being frugul although you do need to drop a few gears if you merge onto freeway from there on.

The reason I does not endorse or discorage use of acetone in this 2.3L engine is that it does not make enough difference (<10%) to warrant the additional procedures after each fill up. Acetone is a solvent for certain type of rubber and plastic, however it does not affect the engine and fuel line seals, not to mention the concentration in fuel is mearly 1.5% by volume. I have read many articles calling acetone "corrosive" or "beneficial" to different car parts. As a chemist, I do not believed any of those claims without supporting data. Try for yourself: dip a used rubber fuel line or engine seal in pure acetone and see what happens after a while. Make sure you seal the bottle to keep the acetone in place . One thing I do agree is that acetone DOES strip car paint which was one of the reasons I do not endorse it for an average person.

 

My 2.0 gets 5 mpg less in the winter than the summer -even withthe A/C always on in the summer.

23/City Winter and 28/City Summer

You get considerably less gas at the pump in the winter and there are other factors that cause efficiency problems in cold weather.

 

No change in gas stations and this didn't occur after a service. Just flipped likea switch from 30 mpg to 23 mpg. I've had 5,000 miles with the gas mileage problem, about 3.5 months. All have my habits, whether they be where I go for gas or where and how I drive my car have remained constant.

 

PAC, this is my 3rd winter in the car and the first winter thatI've experienced a signficant drop in mileage. Yes, I have seen a drop typically in the winter to 27-28 mpg instead of the typical 30-31. I drive 90% highway.

 

I am very upset. My dealer does not know what they are doing. They are using me for a cash cow. I am still getting terrible gas milage. I am still looking for answers. 2008 M3 touring 8500 miles.

 

My '07 has less than 6000 miles and also is getting around 18 mpg mixed (mostly city) driving. It has only been going down since I bought it. My Volvo x-country gets close to 20 for the same time period! This can't be right! What's going on?

 

I drive a 2008 Mazada3 2.0L Auto tranny. This is a new vehicle purchased in March 2008. I track the mileage on my iPhone with an Application program that computes it for me.

DATE MILES GAL MPG
March 19 320 10.03 33.81
March 24 677 10.56 33.36
March 27 1037 10.79 34.08
April 1 1393 10.45 33.76
April 4 1742 10.34 33.93
April 9 2097 10.46 34.05
April 14 2445 10.22 33.28
April 17 2768 9.71 34.38
April 22 3116 10.12 34.28
April 26 3542 12.43 TBD

Overall MPG 33.9

 

i have same problem so ima try something i was told by someone
reset the ecu by disconecting battery and pressing on brake for 10 seconds and let it alone for 5 min before connecting back (it supposed to set you back to stock option the mazda originally come with )

 

I live in Arizona and I actually experience the exact oposite regarding seasonal mileage. I have an 07 GT with the 2.3L. In the summer I get 25MPG, in the Winter I can as much as 29MPG. I drive slowly, really try to conserve gas and these are the best numbers I can get consistently. If I am not being careful to save gas (driving 80 on freeways and not trying to coast all the time) I can easily only get 20-23MPG. I think the Mazda3 just doesn't get very good mileage, not much you can do about it.

 

I have a 2008 Mazda 3 Touring 5 door with 2.3 liter engine and manual transmission. Gas mileage has been very disappointing. Usually get 22 miles per gallon with 50/50 city/hwy driving and 10% ethanol fuel. Using mileage improving driving techniques (efficient gear shifting, slow acceleration, coasting) improves the mileage to a maximum of 23.5. This is really not what I expected when I bought the car. It is not worth the savings in gas coststo trade the car in. So I guess I am just stuck.