That's TERRIBLE!!!
Even w/my heavy right foot (2.3L HB w/5-sp) I can easily get 25 w/the AC on and 28 w/o... and that"s mostly city driving. I just filled up today and got 29 w/the AC off, of course.
It sounds to me like it"s time for a trip to the dealer.. perhaps to re-flash the ECU (to Mazda techs, that"s a PCM.)
I"d have to guess that your fuel map has somehow gone awry. Mazdas are not really known for the best fuel mileage, but you should doing much better than 22 imo.

 

Thanks for your response virgin1. I just made an appointment with the dealer to reflash the ECU. It cost $100, and the service rep did not encourage me to do it. He thinks the mileage is normal. Rep also recommended using some Chevron gas to clean out carbon deposit - but car is new and has always gotten bad mileage. I will post results of this experiment on this forum.

 

Best of Luck, Sir.
I hope it turns out for the best, or at the very least perhaps find another problem while doing the reflash.

 

Yeah, I can't understand the low mpg. I can go over 400 miles on a tank and that's usually only 12.5 gallons of gas.

 

I have a 2008 Mazda 3 Touring 4door with 2.3 liter engine, manual transmission and 22k miles. Gas mileage has been 28 avg. hwy @ 80mph. When I slow it down to 65-70mph i get 29-30mpg. I think thats good. I use Exxon and Shell Oil gas only 87octane. I also use RoyalPurple Oil that helps with mileage. I think it would be hard for the dealer to pin-point why the low mileage. Also check the brakes to see if they are not sticking.

 

I have a M3 s touring 2.3 5sp a/t. Live in central ,Tx. Average 23.4 to 25.3 30% city 70% hwy. i think this is good. Just went on a trip 320 milea at speed between 70-78 mph with cruise on and was supprised that it got 32.18mpg. It seems that speeds above 70mph it gets beter milage.
I think most of the problem is the addition of ethonal and the politicans in Washington that has manduated this forest.

 

So far on my 08 Mazda 3 sedan I'm getting 27-32 mpg. To me it sounds like we are uncovering a valve timing issue with may not show up on computers but is obvious to drivers. Be sure to mention this to the dealers... u may have to grab there tie a bit to get there attention to check it out proper And to add to the post about 35-50 mph in 5th gear... perhaps good fuel mileage, but running at 35 in 5th is very bad for the engine itself, even if u are running on level ground not accelerating this can be harmful and decrease the life of the engine. should never cruise below 1,600 rpm and really never try to accelerate above 3rd below 2,000 rpm. reason for this is the light weight short piston skirts. This engine is not designed to operate under load at this low rpm, balance is not right, causing slop and adventually a failure. This is also known as "Torqueing" or "Lugging" the engine.
Hope this info helps, i know i will be watching my car for this same gas milage issue.

 

okay just an update from my last post. Yesterday i put 160 miles at an avg speed of 95 mph and I got 26.7mpg. I think thats really good. I know I should not go that fast but I was running late.

 

2008.5 MZ3 HB with the 2.3 and MT. I am normally Getting 30-32 MPG with it being a 70/30 split Highway and city, I just went on a 440 mile trip, first tank figured out at 37.39 MPG, I did go down to around 28 driving around in Washington DC but still got better than 33 with a pretty stiff Crosswind on the way home

 

First fillup today on my new 2009 Mazda3 i Touring VE, 350.0 miles, starting with what the dealership claimed was a full tank, and then needing 11.67 gallons to the click-off point. That works out to 29.99 mpg for maybe 75% highway and the rest around town. Of course that's only one tank with an unknown starting value, and given that the car isn't broken in yet I think it will be a while before I know what my typical mileage will be.