Low gas mileage

[Bob]

I have an 1987 Subaru GL 4WD, 1.8 S#jf2an53b8hf457939. I took it into
the garage and they check her out on the diagnostic machine nothing
showed up. Mechanic also took her out for a test drive. He checked
compression cylinders were between 120psi to 135psi. He check valve
timing, checked ignition timing repaired brocken vaccuum lines. Ran on
scope. The wagon is still getting about 20 per gallon. Any ideas on
where I should be looking to improve the gas millage?
Thanks Bob<><

 

[Edward Hayes]

A heavy right foot??

 

[stumpy]

Tires & tire pressure make a big difference. Running underpressure tire
eats gas.