Our '95 Civic is an automatic and has always stayed in 4th until it is warmed-up. You can actually guess within a mile or two as to when it’s going to shift into top gear, and this happens only when cold. The gear selector has 4 selections and once warmed-up will shift into a 5th? (guessing overdrive) . . . and being the car nerd that I am I listen for this shifting sometimes. I change the fluid often, siphoning and replacing a pint every oil change (3000 miles), stays nice and clean all the time. My suggestion for the OP is to find a good independent mechanic (not the dealer and not a chain tranny or oil change shop) and have that mechanic check it out, change the fluid and filter and assess it for you. Rocketman