Simon,
I used to fly A-10 fighters. We took an oil sample after each and every sortie and had it analyzed--even when we went cross-country to strange bases, we carried oil sample bottles--it was incredibly cheap insurance for million dollar + engines, not to mention flight safety. On my own aircraft, I take an oil sample whenever I change the oil, every 50 hours or six months--again, cheap insurance. For my own daily drivers (my wife's car and my pickup truck,) I don't use oil analysis--just change the oil and filter at factory recommended mileage intervals.
For the Morgan, oil and filter changes every six months or 3000 miles, whichever is first, but I don't use oil analysis (maybe I should.) This just makes a lot of sense to me.
Conventional, synthetic or semi-synthetic oil--that is a different discussion. Additives are another discussion as well.
Allen
'69 4/4
