Car is at 118.6k and changed plugs about 7k ago...prior to plug change i was averaging 19.2-19.9 or so....after plug change to denzo fxhr 24, getting a consistent 18.8 ...some posters mentioned improved mpg with new plugs AND car felt peppier....me= less mpg and meh at best no noticeable increase in performance ...go figure...unplugged battery for 15+ hrs...same

 

Those sound like the wrong plugs accordign to google the gap is 0.027" oem gap is 0.044"

 

These are Denso FXE24HR11 Plugs are pre gapped but I believe they checked etc...car is smooth and under acceleration no issues...just not the improvement I've read from other posts and what I was hoping etc...less mpg and no back to newish power, so who knows.....but thanks

 

I just drove from Benson, AZ (3500' elevation) to Reno, NV (5,000' elevation) pushing 75-80 mph the entire way (made it in 15 hours by myself)...here are my numbers:

Fillup #3
286 miles
9.77 gallons
29.27 mpg (the best mpg ever for this car)

Fillup #2
311 miles
11.197 gallons
28.22 mpg

Fillup #1
358 miles
12.933 gallons
27.68 mpg

Total miles = 955 miles
Average MPG = 28.17 MPG
Ownership MPG = 25.7 MPG

Car has 126,600 miles on it.

 

My stock '13 G37x gets 11~17 MPG in the city, and 27~31 MPG on the expressway when there's no stop-and-go due to traffic.

Curiously, the in-town mileage doe not change if I carefully try to drive with as little throttle as possible or if I just blast around.

FYI it is my belief that mileage actually increases when I am blowing the doors off BMW's or VW GTI's at stoplights.

 

Just know that you can dip below 10 mpg at a track event.

 

I'm averaging about 17mpg, but I mostly do city driving with a lead foot. I haven't paid for gas in a year and a half so I don't care about the MPG. lol I get a free fill up a week from my company (and oil changes/tires) even tho I'm not driving for work, just a company perk.

 

Around 18 mpg with 70 highway 30 city driving