Taiwanette asked her uncle, and he gave her an old-stock magnetic oil filter which, AFAICT, seems to still be manufactured right next door in Kaoshiung (Gaoxiong). 150NT.
No idea how effective its likely to be, and I don't think I'll fit it until I implement some means of evaluating that (which may never happen), but even so its slightly intriguing. From the picture on the box, its an in-line magnet like the Magnaguard,
http://www.magna-guard.com/MagnaGuard.html
but it comes "built-in" to a throw-away spin-on filter.
http://www.hiwtc.com/products/s-n-power-auto-magnetic-oil-filters-1377795-71173.htm
The leaflet in the box makes some fairly risible claims, (see below) which don't prove its useless, but don't exactly inspire confidence.
"THE EFFECTION OF MAGNETIC OIL FILTER
Idling RPM of engine will speed up 20-50 RPM after running 30 minutes and CO, HC will be reduced to 50% simultaneously [This sounds like its warming up, and unrelated to the device.]
After one week idling RPM will increase up about 200 RPM and CO, HC will be reduced to 50% to 90% simultaneously
Temporarily increasing of CO means decreasing of carbon"....etc, etc