I skip from 1st to 3rd and/or 3rd to 5th if I have enough momentum to keep from lugging the engine or if I'm shifting while going downhill. 3rd to 5th seldom causes any problems at all, 1st to 3rd can be tricky at slower speeds or around town. In the 4 cylinder Escorts I drive if you try skipping gears while on an uphill grade it usually lugs the engine more than I like. In the '88 Escort Pony with 4 speed I'll sometimes skip 3rd gear. In the '88 I really can't say I notice an increase in mileage, I just get lazy. In my '97 wagon the Scan Gauge reports higher mileage when I skip 2nd, not so much skipping 4th.