Man did my gas mileage just go way up recently. I can't think of anything different on my car except my new NGK spark plugs. I still drive the same. Before, I was getting maybe 300 to the tank and now and I am getting 340-380 a tank. Is this possible?

 

sure it's possible, but you have to take some things into consideration.

Are you driving from a full tank to bone dry (meaning completely empty, till the last drop of gas is gone)? Prolly not right? Then a MPG calculation would be more accurate and you should base your conclusion on more than one tank full to see the actual trend in MPG. Could have been you've been driving better and that could have added to the fact that you have been getting better gas mileage.

But getting new plugs can definitely improve gas mileage, especially if your old ones were in need of replacing.

 

They told me that spark plugs can only effect the MPG about 3-5%.

 

knock sensor... o2 sensors i think work the best...

you can also clean ur intake/throttle body... that might make some good too.. i'm sure there is more u can do but that's all i can think of as far..

 

a dyno research once stated: with bad spark plugs, the car may scarfice 10-15HP at crank, which hurts performance.

my max hasn't been starting at the normal rpms. i know my OEM sparks probably died out. therefore i picked up some NGK 1 step colder spark plugs and installed it. now my car starts fine at the correct rpm range, and milage gradually went up as well.

the reason i choosed 1 step colder because there is a big tendacy that i mite run nitrous application in the future.

 

My car starts at 1500rpm or around there, that is normal as far as I can tell. After a warm up they get down to 750rpm...