i'm running JWT pop charger, HFC, y-pipe and my car isn't getting good mileage. After many searches I decided it's best to replace the spark plugs. Can I use NGK Iridium (LFR5AIX11) or the OEM Platinum plugs? My car getting 14.7 mpg and 17 mph which i think is low.

 

Iridium is fine. thats what I just replaced mine with.

 

holy sht!!!! going downthe highway doin 65 to 70 i get 27 to 28 mpg in town i usually get 23mpg

 

How many miles do you have on your car?

 

+1. i have gotten up to 36 mpg 6th gear cruising on 95 going 80 mph with the car under heavy load on a clear brisk day. at least that is what my read-out said, i dont really believe it, but hey, it looks good on paper.

my average mpg under normal conditions is 26-29 mpg on the highway, depending on how heavy my foot is that day, and i get between 18-20 in town. if you are getting low mileage i would def start with the spark plugs. 45k on the odo.

 

i usually avg 24 (calculated every fillup). go with the iridiums. not sure how much that will bump up your mpg tho.

 

30K