leaning out the fuel mixture "a little" should have minimal impact on cat life. In fact, dumping too much gas on the cat can also have adverse effect. Cats I believe are federally mandated to have a 100,000mi life and Mazda is just making sure that most if not all cats make it that far to keep warranty repair costs down.

I guess it comes down to what your comfort level is. I for one would like to lean out the AFR "within reason" and tune the engine to produce better performance through proper tuning using either the Interceptor-x or another one like it. Since the car would be a daily driver I am not planning on going WOT all the time, which should help keep the cat temp down.

 

Thats amazing people get that bad of mpg?? There has got to be a problem somewhere. I have never gotten below 18.5 mpg when new and now i'm always right around 20mpg. That is a huge diffrence between same car, even if I drive like grandma and someone drives like Mario mileage shouldn't be 2X diffrent for the same car. I have the M-flash and the new plug recall.

 

it seems the people with the new plugs are getting good mileage, my stupid dealer just wont change mine

I'm getting between 15.5-and 16.7 since i bought the car 3 months ago. It's awful. The other day i did 90 miles before fillup, 50 that was freeway full freeway, 70mph, other 40 was a mix, when i filled up i got 15.7 mpg. I almost threw up.

BTW- i have the recall flash R.

 

^^just change the plugs then... spend the money now if you think it will save you in the long run.

 

where do i buy the hotter plugs?