Open any owner's manual and the schedule reads "every 12 months or 10,000 miles, whichever comes first". That sentence is why vehicle maintenance is hard to track in a calendar. A calendar knows about months. It knows nothing about miles.
Two clocks, and the faster one wins
A car that does 4,000 miles a year is on the time clock; the oil ages whether or not you drive. A car that does 20,000 is on the distance clock and will hit the interval twice before the year is out. The same reminder cannot serve both, which is why a flat annual nudge is either early and ignored or late and useless.
What you want is a system that holds both and tells you which one is about to trip — and that can say "about 900 miles away" as well as "in seven weeks".
Which needs an odometer reading now and then
Nobody wants to log mileage weekly. But if you enter a reading occasionally, the gap between readings gives you a rate, and the rate gives you an estimate for today. The estimate is not a fact and should never be shown as one — but it is enough to know whether a service is a month away or a season away.