What size cas tank does the 1985 Honda Accord SEi have?

You can go to www.fueleconomy.gov to find how many MPG the EPA says you should get. But, it really depends on how you drive. For example, I drive a 96 Accord 25th Anniversary Edition that has an EPA rating of 20 city/28 highway, I get 40 MPG on a regular basis. As far as the tank size you should be able to find it in the owners manual.

The tank size is just over 15 gallons, closer to 16. With my 5 speed manual model S, I get 35mpg going 60 highway. And about 28-32 going 70 highway.