I have been running about 5k mile change intervals with Royal Purple synthetic. Per Blackstone analysis, I could be going a good bit further. Is there any reason why I shouldn't run 5k, drain 4 or 5 quarts, top off with fresh oil, and run to 10k before doing a complete change? Would my big powerstroke filter (Napa gold, FL1995) handle 10k? Thanks. I drive about 9k miles a year if that's relevant.