Why would an anti-drainback valve be preferable? I like the fact that when I change the filter, it's empty. Especially given the upside-down mounting. I suppose the anti-drainback valve allows the engine to build oil pressure a bit quicker, but is that such an issue with a rotary due to the rather short oil path compared to piston engines? I'm going to try a NAPA gold filter next oil change. And the Purolator filters dent just as soon as I start to tighten my metal strap type wrench, I'm not overtightening them by any means.

 

how about the K&N oil filters, are they any good?

 

the anti drain back valve keeps the oil in the filter. This way, your car gets lubrication sooner bc oil doesn't have to fill the filter to get to the engine. This is critical in an up side down filter.

the napa silver doesn't have the valve. I discovered this when I revisited Napa when I returned something else. Gold costs $6+ so I will stick with OEM instead.