Well I guess everyone gets to weigh in on the temp gauges. If you add the gauges what would you do with the DATA???? Is it like the comment on an airplane - engine shuts off at a certain temp??? Should we shut off the engine at a certain temp??? Probably not or it's just going to heat up more since there is no air flow as someone already noted. Outside air temp apparently makes a difference. Do you not use the tractor because it's 90 or 100 outside??? I don't know if it's worth a hill of beans, but what or what do you do with the info (DATA). For my money, the tach may be more useful if you're gonna add a gauge. But then again if it's hot out do you run at slightly lower rpm's (3200 maybe?). You get less air flow and doesn't cool as much. What or what do we do with the data. Charlie may just have the best position. Don't worry and just enjoy using the tractor.
NOW - on the oil. Ole KenTUCK has been at it in the Sand Box, but the oil debate will never end. Having read Art's link it looks to me like all this stuff might be "hog wash" (hehe). Everyone's got their own idea of what may be best and may be needed. I got really worried on the ZDDM or ZDM, or zinc missing, but it seems on the little scientific info I see, the newer oils are lower in ash, and for my money that may be worth more than less ZDM. I think I'll just stick with my Valvoline 30W which has always worked well for me. One thing tho, going back in the Forum history to the "Original" Great Oil Debate, in the days BTGC (Before the Great Crash as some of us may remember), the greatest comment I recall was one past along from an Old Timer - quote "Oil is Oil, and some is better than NONE". For my 3cents, take care of your engine, keep the oil changed often, and at the full mark, and you should enjoy a long engine performance life.
Hydro Harry
Old Cubs Never Die (and they love their oil changes)