Here’s a technical question about fuel economy. My father-in-law, who lives in Europe, has become a strong advocate of an idea that supposedly saves gas: 1-3-5 shifting. The idea is: in first gear, accelerate to a speed where it’s possible to shift smoothly into third gear, totally eliminating the first-to-second shift. Similarly, in third gear, accelerate to a speed where it’s possible to shift into fifth, thus avoiding fourth.

Can this work? Obviously, you avoid stomping down on the gas pedal for the 1-2 and 3-4 shifts. But you also run the engine at higher than normal RPM in first and third. Is there a net saving? Would it make a difference if the car had a carburetor or fuel injection? Will the higher RPM cause additional engine wear?

-Dave S., Calif.

An interesting theory Dave, and one I’d be tempted to try, except for one thing. It’s tough on the transmission. Several manufacturers have released service bulletins or dealer advisories recommending against skipping gears while shifting. Apparently skip-shifters are encountering a higher incidence of synchronizer wear than those who operate the shifter in the proper sequence.

Synchronizers prevent the clashing of gears by momentarily blocking each shift until the two meshing members are brought to the same speed, then are locked together. Skipping a shift typically results in a greater speed variation between the meshing parts, accelerating wear of the synchronizer’s brass or paper-faced cone clutch.

Operating an engine at reduced RPM is a good way to improve fuel economy, as pumping losses are reduced. Up-shifting a tad early during mild acceleration, as well as holding the highest gear possible at steady speed are worthwhile endeavors. With practice, one can find the bottom end of an engine’s happy range – a load/RPM balance that provides smooth performance, some margin for mild acceleration, while reducing fuel consumption.

Larger engines are more likely to tolerate low-speed operation – perhaps down to 1,100 RPM under light load, while smaller, higher-revving engines might sputter or play possum if loaded more than a bit while below 1,500 RPM.

For spirited acceleration, particularly when merging into traffic, one needs to abandon this stodgy strategy, drop a gear or two (in sequence), and pour on the RPM.

The best things one can do to improve fuel economy are to keep up with engine-related maintenance, check tire pressure regularly and consolidate trips, which minimizes fuel-wasting, high-emission cold starts. Anticipating slowdowns – coasting to an upcoming red light, rather than driving, then braking to it – also can save gas. Also, remove any unneeded items from the trunk or storage area. The less weight one lugs around, the better fuel economy will be. Turning off the defroster as soon as it’s no longer needed, and using the vent function rather than A/C during mild weather also can improve fuel economy, as the A/C compressor places a fuel-consuming load on the engine when in use.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose.