I'm only getting around 24-25 mpg avg. daily driver mileage. 139,000 miles currently. Been thru all the basic tuneup stuff, NGK G-Power plugs, new wires, dist cap & rotor, new PCV valve, valve lash checks good cold, timing belt looks good when cover was off checking valves, new thermostat & radiator (old one was leaking a little at top tank crimps). No oil burning (< 1/4 qt. in 6,000mi. on Amsoil 0-W30!) Been on Amsoil since 35K miles. No MIL codes, starts right up easy from cold, idles smooth always, good acceleration & power, just mileage isn't what it should be. I burn 89 midgrade only, 87 will ping slightly. Timing checks OK. I have tried Techron, but no real improvement. I got a different treatment to try soon, Lubro-Moly Jectron for FI cleaning, and Ventil Sauber for intake valve deposit removal, about $4 ea. What else should I check out? Do fuel pressure regulators ever become stuck, or need replacing at high mileage?

 

How is your O2 sensor and catalytic converter?

 

Will have to probe the voltages on the 02 sensor and test. Have to pull the cat out to look at it, or what other way to know if it's clogged? No emissions checks anymore here in Florida, will it hurt to rod out the screens and run it open? Or what's a good replacement cat for Civics, other than $$$ OEM? Just a daily driver, but want to keep it in good shape

 

check timing....