Better fuel mileage

I trying to get a little better miles per gallon, any ideas would be greatly appriciated.

i have a 2002 with 4 liter and 5 speed AUTO. has 40,000 miles. had it since it had 20,000. i was getting about 17 on the highway during the winter, think i was 18.5 last summer. i was using 10w 30 motor oil and regular gas. in the last month companies have switched to summer blend gas, and i try to buy 89 octane gasohal. I bought 5 w 30 synthetic oil for a test, try to keep my speed about 62 MPH which is about 1800 RPM, and spend a lot of time on the highway, only 20% around town. last two tanks were 20 MPG and 20.5 MPG. not sure what works, but i believe a combination of the above have each added a little. Heard a story about the air cleaner restriction being a little high, but i have not tried anythign there. at 1800 RPM i would not think much air restriction was present. Make sure proper air is in the tires also.

My 2000 has gotten 20 mpg consistently since new.
I'm lightfooted and keep the tires at 30 psi.