95 VX City MPG not as expected<--Have Searched
 

I have a 1995 Civic VX with 132k miles on it. I use this car mostly driving around the city. When i got it, before tuning it up i got 31mpg (1 tank before a tune up), after the tune up i'm getting 35mpg, which is better, but it is still not what others I have seen are getting. The tune up consisted of, -NGK Copper plugs, NGK spark plug wires, New Distributor Cap, Rotor button, and Fuel filter, as well as a Synthetic oil change and Pure One oil filter. I was running 205/50 15's in the front and 195/55's in the rear (for auto crossing). Since I have put the 195/55's back on all 4 corners. And still at 35mpg... I have yet to test the LAF and see how Often I am in LB, but I plan on doing that this weekend. Would a possible bad ecu be causing the poor gas milage? or maybe a bad LAF? I would really like to be getting 40mpg city which is the window sticker. Also would adjusting the valves help with better MPG? It is due for a water pump/timing belt and tensior soon, so I'll adjust if it helps!! Any insite would be great... Also my tire PSI is 40 all the way around. the car is also lowered with coilovers but not sure if that helps aero that much with city driving. Thanks for input!! And please help a newb to the MPG cause!
Car is mostly stock also, after market cat-back exhaust
Factory airbox with K&N air filter with fatory restrictor removed(inner fender and all that junk)

Yes, a bad oxygen sensor could be causing your low mpg. You will also need to be upshifting when the indicator light tells you. If you have a california car, just upshift at as low rpms as possible without causing any type of growling noise.

Getting the stock size wheels and tires will also help reduce unsprung weight which is important for stop and go mpg.

It is a 49 State model, so no Cali. version. I usually shift either at the light or before it. I try not to get above 2500 (vtec engagement point??) and pretty much just poke around town. As far as wheels. The 205/50's are mounted on 12lb rims, and the 195/55's are on stock si wheels (which i know are pigs) but looking to stick with a 15 (light weight is what i'm looking for, I am aware of the unsprung weight from auto-x), or some HX 14's if i can find them.

Adjusting the valves would definitely help as evidenced by another user's experience. OP, if you're cruising on the highway at 55mph or 60mph, how many MPG are you getting? If it were a little low, it'd definitely be something to look at. I have no idea how conservatively you drive your vehicle so being able to find your cruising MPG would be sort of helpful as it would be able to eliminate some variables.

Might want to try a leakdown and or compression test?

Check the coils to make sure they're still good? If you're serious about this car, get yourself a service manual so that you can test every little thing here and there.

Also, OP you need to go back to your stock wheel size and tires because those wheels+tires are going to drastically affect city mileage regardless of them being alloy wheels, not to mention the fact it will throw your odometer off.

VWtoHonda,

I just went from VX to VW (actually still have both). Please let me know what VW you had and what you didn't like. I've had mine two weeks and enjoy it so far.

Larry

Regardless of whether or not you think the rims are light, the tires are most certainly not light because low profile tires for the same diameter weigh more than large profile tires (large sidewalls vs small sidewalls).

Since you have a Federal car, it's possible you're not ever going into lean burn which would hurt your mileage, though not going into lean burn alone wouldn't hurt it THAT much. BTW, there is a guy on here who was getting like 48-50mpg in his VX and when he adjusted his valve lash, it improved to like 53mpg. Either way, regardless of whether or not replacing your O2 sensor fixes anything, you should still adjust your valves because that way your valves will open and close at the right time.

I find that I get better mpg if I simply stay in leanburn as much as possible ,even in the city . I have a leanburn indicator light and also a mpguino in my car so I can see instantly that the mpg drops like a rock as soon as you loose leanburn no matter what the shift light says. With the engine warm and under light load you can feel it go into leanburn (wider throttle opening for the same speed is a good indication of entering leanburn mode) . Open the throttle too much an you will loose it.

Yeah, well that's pretty much why the Lean burn VX gets better city and highway mileage compared to the non lean burn VX.