I just bought a used 1999 honda accord ex v6(50,000 mile). I got
average 20 mpg.

1).Some accord v6 owner said they got average 28 mpg. I'm wondering if
there is anything wrong with my car.

2).The idle speed is a little above 1000rpm , but the dealer said it
is normal.
The manual said it should be 750

3).The rpm for 60 m/h is 3000, 80m/h 4000 , I'am wondering if it is
too high.

4).The car is running fine as far as I can see.