Civic EG

I would like some ideas on how to improve and fix my mpg. I was getting 35-40mpg before but for the past 3 months, it has dropped down to 28-33mpg... (Not running the a/c) I have changed the spark plugs, ignition wires, and fixed the evap vaccum line. Nothing helped. I have changed oil frequently too. Other ideas I have would be fuel filter? Injectors? I have a brand new air intake filter. I did go from stock oem tires 13's to 225/50/r15s, but i doubt the gas mpg would get that much worse. tire pressure set to around 33 psi. I am really not trying to guess and just keep throwing parts at it...

That's a drastic difference in wheels/tires. I get about a 3mpg drop with just same sized snow tires compared to all season ones. I bet that's a large majority of your problem

http://www.miata.net/garage/tirecalc.html

Use the tire calculator. It’s a big difference in circumference and in contact patch.

225 is a lot more contact to the road than the oem 175 size, especially if that 225 is a performance tire. That's a lot more rolling resistance = lower mpg.

Also might want to get your alignment checked. A bad alignment is going to affect mpg a lot more with a 225 than a 175.

Thanks guys. I have gotten an alignment from acura for it. Well, the lower mpg have started around the time of getting the 225s. I try swapping out back to factory 175's. Motor is a jdm d15b non-vtec. Manual. And no cels.

Winter blend gas could account for part of it. Wider tires and winter gas could easily add up to that much loss in fuel economy.

You may not be getting as bad of mileage as you think. When you change the tire diameter it throws off your odometer enough to affect your measured MPG.

I will swap the tires back to stock and just see.

update, kept the wheels on and swapped to a popular busy QT gas station. Mpg shot up to 36mpg.... it was about 29-31mpg with my neighborhood BP gas station. I guess I won't be going there ever again. lol