I have been noticing the mileage dropping to under 20 mpg.  I changed out the plugs with standard NGKs today, care runs very well.  I checked the air filter, cleaned it out.  Are there any other good candidates that could be causing this?

 

The plugs were down to toothpick points, they are not easy to do unless you have quality tools.  

dragging brakes.  if the rear brakes are as trashy as the fronts were in the other discussion then look at the rears and make sure they freely slide on the pins and the pads aren't hanging on the clips.

 

read check engine lights. 

 

driving style - if you're doing stop and go driving, idling, etc the car isn't going to get worse mileage. 

 

calculation - are you actually calculating mileage or just looking at "miles per gas gauge"?

I've been using the gauge, I didn't realize they are unreliable.  

 

Could be the gas additives, they always seem to lead to poorer mileage in the cold months.

 

Car runs very well, no drag from brakes or other sources when in neutral.  MPG around 20.  

20 isn’t unexpected for city driving. Are you positive you should be getting more?

 

Have you actually pulled a wheel and checked the rear brakes? They don’t need to “feel” like they’re braking to impact mileage. A consistent imperceptible, light drag would be enough and you’d never know it.

 

Pull knock sensor and install an eBay $8 cheapie. They’re easy - one 12mm bolt and the most common sensor to cause issues. But without a code it’s probably not that.

MPG can be subjective. Flat open highway with cruise on for an extended period can usually give an accurate sign of how it's running, or how well it can/can't run. The rest will depend on your foot and the terrain. Newer cars with real-time MPG read outs are helpful. I used to tow with a car and at times was pulling around 4k pounds (car) another 4k+ (dolly w/ full-size F150, GM van, cars, etc.) and real time for that car would drop to 10 MPG highway from 32-33 highway. I was constantly traveling out of state, so it was easier to see the numbers fluctuate.

 

A full tune up is always smart. NEW air and fuel filter, new plugs, new wires, synthetic oil, good road tires, and putting the car on a diet are all good ways to incrementally bump up MPG, as well as what Idosubaru mentioned. If possible, lowering the car, adding a freer flowing muffler (high mileage stock muffler could be deteriorated internally to the point it's becoming restrictive to flow), possibly new O2 sensors if high mileage, etc. can all be things that might be hindering MPG or might be able to bump it a tiny bit, and might as well replace all vacuum lines while at it so everything is working as it's meant to w/o possibly leaning out or erratic sensor readings. I will say my '95 ej22 (with basically everything above replaced/done except exhaust, O2, and lowering, gets kinda abysmal MPG. The 33 mpg highway mentioned on the previous car weighed roughly 4k pounds with me in it + tools and sub box, and had a V8 with auto. My ej22/4eat can't even get close to that.

Edited April 13, 20187 yr by Bushwick

I would kill for 20mpg city

I'd kill for over 17mpg lmao

Edited April 16, 20187 yr by comatosellama

+1 knock sensor