I get all fluids at the dealer when I buy the oil filter.
My hours are getting lower every year so the fluids tend to last a long time.
Oil is changed by the calendar and not by engine hours.
I bought a high performance sports car back in 2017. Owner's manual says change the oil every 6 months regardless of the miles. Sometimes the car sits in the garage for 6 months. Not driven.
I changed it a few times every 6 months and watched clean new oil drain out. Now that the warranty has expired I change it every 3,000 miles, even though the dash guage says oil life is at 70 percent.
But, if you use your equipment all the time, a calender is an easy way to go. Definitely.
My motorcycles, ATV's, lawn mowers, walk behind snow blower and log splitter oil get changed by the calender. I reuse my car's oil in my cheaper mowers.