and yes, Honda/Toyota have their fair share of mechanical troubles when they try to push their mechanical design envelope further in compliance of emissons and economy. Why would sludge problems happened mainly to NA customers? In Japan, most service centers, mechanic shops, etc. already using semi-syn or full syn when servicing their automobiles, and with very strict emissions and automobile inspections (you need to pass them before you can renew your insurance and legal to drive on the road). Vehicles there typically goes for approx. 6 yrs before their inspections become so cost prohibitive that they would rather sell/scrap them and buy a new one instead.
Here in NA, automobile owners typically covers more mileage and per mile basis, perform less maintenance and inspections and emissions than many other industrialised/post-industrialised countries that I'm aware of. Sludge in this case, would be a common occurance (IMHO, YMMV). While you may wanna cry foul on this issue but I've seen many avg joes/janes pushing their minilube bulk oil job through 10,000miles and beyond and though that gawd would help them in keeping their cars on the road for 10+ years. Not possible anymore, I'd say, unless you are driving a 1950s automobile and try running API SM/SL grade dino motor oil....LOL!
Ok, enuf ranting. back to my work I go.