Car in my sig has 4k miles and 8 months on current fill of M1 10w-30 HM and OEM Mann filter. Factory OCI is 5k miles, as the turbocharger automatically puts it in the severe service category (according to late 90s oil tech). The NA version of the same engine has 10k for normal service and 5k severe service. It does see relatively severe service in general, with a 50/50 mix of highway and city driving, occasionally loaded to capacity or towing a half ton trailer. However, most trips are longer than 15 minutes and it has an oil to coolant heat exchanger, so it never gets put away with cold oil. System capacity is 7 quarts and I've added 2 quarts make up oil due to leaks and repairs thereof, so plenty of oil and add pack available to deal with contaminants. While I'd suspect the M1 could go longer, I want to get a UOA to see how things are doing. Question is, should I take the sample now so when I hit 5k I have the report back to make my decision? Or do I sample when I change it at 5k, with a good chance I'm dumping out oil that is still quite serviceable? I don't want to extend beyond 5k in severe service without the UOA data.