Just 10-15 years ago, your tractor was probably factory filled with a 15 weight conventional oil, so all your A and B service intervals were built around that and your oil changes were probably with the same factory fills. Over the years those factory fills and OEM recommendations have changed and not all fleets have kept up.
00:00 10-44 intro
00:28 Changes in OEM recommendations
01:12 Synthetic blend vs. conventional engine oil
02:21 Synthetic blends and full synthetics
03:28 Older equipment
06:36 Lightweight engine oil and power