I cleaned my throttle body, and when I started the engine after, I saturated my plugs with the residual cleaner left inside. I didn't know this until my mechanic said it just needed new plugs. Little did I know he put in these bosch plugs (I have heard these may be bad for maximas.

I had champion gold plugs in it before and they worked fine. I got around 25mpg driving and equal mix of city and highway. I just added a k & n air filter (stock filter size, not cone filter) and now my gas mileage has gotten worse (20.3). The plugs are the only culprite I can see. I don't drive my car hard since it has so much power (rarely go past 4500 rpms). Any information would be appreciated.

Also, what kind of gas mileage do people with the ngk's (factory plugs) and a k&n installed typically get, driving there cars like I do? thanks

 

Bosch plugs are bad news:
http://maxmods.dyndns.org/index.php?MaximaSparkPlugs

 

you are suppose to use ngk my friend