Wow, I just changed my spark plug with stock NGK heat range type (around five bucks apiece x 4), and my gas mileage went from 21 to 25 mpg mixed city / (mostly) highway. I don't go easy on this car and it has a street port, so I'm surprised that it has responded to fresh plugs like this. It even has heavy wheels and stock exhaust.

Piston cars will run fine on fouled plugs I guess. I've only owned this car for about 7k total miles, and it was on the plugs it had when I bought it. My Integra would never change much with new plugs.

The $22 spent on new plugs should pay for itself in exactly 1498 miles, based on the current price of gas ($2.159 around here).

 

Yeah, it's amazing what plugs will do for you. Speaking of which, I really need to change the plugs in my Turbo monstrocity before i foul them to all hell and back.

 

hmm looks like a trip to the local auto store is in order!

 

old plugs + wires + o2 sensor = 12.5 MPG average.

New plugs + wires + o2 sensor = 24.5 MPG average.

WOOT.
they paid for themselves in like 500 miles lol.

 

how hard is it to replace the O2 sensor, and how much?

 

especially with gas prices so high right now it's cool to have those extra MPG

 

Yeah, the 13B eats leading spark plugs... you could go the factory recommended interval, but they are really shot by 10-12K miles.

 

yeah i've noticed my milage is at its best only for the first 2-3 tanks after a spark plug change...thats only like 700 miles and then it starts going down 1-2 mpg every few tanks it seems.

 

I've noticed big improvements on all my rotories as well with new plugs. I need to swap them out on my 'Vert this weekend! I'll post some before/after mileage if I can remember. It should be fairly accurate because I drive the same 100+ mile route on a daily basis and always keep track of gas usage.

 

The local price of gas just went up to $2.239/gal. It will probably keep climbing. A new O2 sensor is looking pretty cheap all of a sudden.