500SEC low MPG
 

My 1985 Euro SEC only is getting about 13 MPG on the freeway.
Any tune up suggestions for improving?

The car passed emmisson standards for new license tags about 6 months ago.
The oxgen sensor was relpaced as part of the tune-up. I also leaned out the fuel, but reset after passing the emmissons.

Timing is currently set at 10 degrees ATDC Vs. engine manual 18 ATDC primaily becausee of lower octane fuels in USA.

The idle after warm up is high at 1000-1300 RPM, which might be part of problem. After setting briefly, 5-10 minutes on short errands, it restarts and idles at more normal 700 RPM.

Timing is wrong and if you have an O2 sensor you need to adjust your mixture so that the car is in closed loop.