[PaleMelanesian]

For us on this site, there's another bigger benefit to low-power lights. The direct gas savings aren't much, it's true. However, if the lower battery drain allows longer engine-off coasting at night, that's a big win. Better to have low power lights than to keep the engine running just for the sake of powering lights.

Let's say you're in neutral, so the engine is idling. Mine idles at 0.17 gph.
Let's say the low-power lights allow 10% more engine-off time.
0.17 * 0.1 = .017 gph saved
$3 / gal = $.05 / hour saved
$50 retrofit lights / $.05 / hour = 1000 hours driving time to break even.
I commute an hour each day (1/2 hour each way), so that's 3 years. If I had a bigger engine the payback would come sooner.