Carla,
A bypass filter taps into an oil line where there is low pressure and filters a small amount of oil at a time. Apparently these filters can screen out particles as small as .5 microns which I think is pretty amazing. I think one of these filters with Mobil Delvac 1 would be an ideal set up. As for cost, I forgot exactly how much it is from Amsoil, but I remember it being close to $200. Is it worth it? I don't know. But, I really want one so I'm seriously considering it. Hope this helps.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside