Hey guys. I have a 04 mazda 3 2.3L and when I first got it in feb. I was getting about 22 mpg. I recently installed a K&N CAI and after that I was getting about 25-26 mpg but now it seems like everytime I fill up im gettin worse and worse mpg. In the last 2 months ive seen my mpg go from about 26 to about 17. Does anybody know what could be causing this and how to fix it?

 

Check your tire pressure. Mine did the same thing...was only getting like 50 miles to the first quarter tank. Put some pressure in my tires and I got back up to 80 on that first quarter. On the highway, I usually get 90.

 

thanks for the help. the tires i have on it are differet. the 2 front are the same and the back tires are 2 different brands. do you think that might be a problem?

 

That shouldn't matter. But low air pressure increases your rolling resistance. Mine were about 10 psi down.

 

As others said, start by checking air pressure. As the weather gets colder, tire air pressure will go down with temperature. Check it frequently. Also be sure that your brakes release properly and don't drag. I once had a defective caliper cause a problem that reduced MPG. I'd expect that you should at least be in the mid-20's for MPG.

 

i think it was the tires. i just got new studded snow tires and im getting alot better mpg on ice!!! Thanks for the help guys.

 

I've been having the exact same problem...entirely same situation. but my tires are inflated to what panels and the drivers door jam says they should be at. 32 psi...
Should I just increase the psi and disregard what the panel says?

 

What is the recommended tire pressure, 32PSI ?

 

From my experience, 32 PSI works about best overall. You can go higher in pressure and get improved MPG but you may wear the tire's inner tread and have a harsher ride which works your suspension harder and could lead to front end getting out of alignment if set too high. This is because the tires will then absorb less shock from bumps and pot holes making the suspension and linkage parts more prone to being slammed out of calibration. Tire pressure is determined by a number of factors besides MPG; manufacturers usually consider these factors to arrive at the optimal tire pressure value.

MPG on my 2.0L '08 Mazda3 was 27 (worst); best was 39 MPG (all highway), usually 33 MPG combined, mostly highway.

 

Tire pressure isnt going to make your MPG's drop to 17. You should check your park plugs and clean your MAF sensor.

 

mine is missing the pipe that directs the air into the filter housing. I only have where the filter is placed. I don't have the pipe that goes from the bottom of the housing to near the bumper. Does this would affect my MPG?

 

I agree with richierichness, tires will contribute to the MPG equation but only 3-5 MPG typically. Check your air filter, spark plugs, MAF sensor, and "oh don't forget" if you have a bad O2 sensor, that could knock you down considerably on MPG. I have personally seen on my car a 6 to 8 MPG drop with a bad O2 sensor.