hi, my other topic on sluggish acceleration is not related to this as this happened quite a while ago.

well anyway i had a check engine error last time and found out it was the o2 sensor. mileage was bad during that time, obviously coz the o2 sensor needed replacing. well, i replaced the o2 sensor, CEL went away and thought everything would be back 2 normal. but it just improved slightly. then i found out that the sensor i changed it with was not from a b18c-r even though it was a four-wire type. so i managed to get a proper b18c-r one and changed it thinking that then it my mileage should definitely be back to normal. but im still getting around 100+ km less than what i used to be getting which was around 450km easily on a full tank. now im getting just over 300, maybe 320 or so.

ive tried checking a few things,

-no fuel leaks
-in my other thread i mention a leaking gasket which supposedly has been there for a while, after fixing that it's still the same.
-air/fuel ratio seems to be very consistent as per the last dyno

i dont know what else could cause this. my usual driving style is minimal vtec engagement and even then for very short periods. i used to be able to get around 450km with that. now even if i dont engage vtec at all im getting really bad mileage.

any help is appreciated.
thanks alot.