Thanks for such a fast response. I have a 97 civic hx manual. I have good news guys. I refilled yesterday and drove 63miles per hour on the freeway for 287 miles and my mpg was around 40 (it appears like I used around 7 gallons but I haven't refuelled yet). It seems like the o2 sensor did it for me
Now I think I didn't get good mpg (33) on my first tank on a new o2 sensor because I was driving 80 miles/hr the whole time. I tried to keep my RPM around 2500 this time around. Do you know what's the best range of RPM to keep my engine in lean burn without going so slow. It'd be nice to go 70 and not 62...