Operating hours versus mileage for oil changes?

In the marine world they use engine hrs; if you have a fuel flow meter you can also measure fuel flow as another guide. Most marine engine companies recommend an oil change between 50-100 hrs.
250hrs for a NA non DI engine seems to be norm, they are easy on oil.
I change oil at either 6k km (4k miles) or when I reach 150hrs, I know it's early but Sportage has GDI engine and my wife doesn't drive much last three years so I get close to 1 year mark on Forte before it hits either mileage or engine running hours limit.
Both Kias have trip meters that show mileage and running hours for both T1 and T2. Neither car has oil life meter or service minder so I use T2 on both to keep track of miles and hours from last oil change in addition to my Excel records and windshield sticker :)
How does one track operating hours? I would imagine it would involve modifying the car to add a counter gauge? I don't think I've ever been in a vehicle that included an operating hour display.
I have 3 that do, 04 tahoe, 2015 gmc, 2020 silverado
Is anyone using engine operating hours instead of mileage for oil changes? I would think that if you spent a lot of time in traffic your operating hours would be high versus your mileage. Therefore low miles but more stress on the oil. Any good studies or experience on this? Thanks
I think it depends on driving and operating conditions. I can clock big miles in low hours but still change the oil at around 5-6k. One time I pulled my RV for 5500 on one oil change and the other, drove to work and back only............oil analysis would answer that question, or at least give a good guide
I always wondered why cars are sole measured on milage rather than operating hours. Also maintenance wise but especially for the used vehicle market.
"normal'' people expect paying top dollar prices for a low milage car will guarantee them to be fault/problem free and that a high milage car will be a money pit for sure where it will be a question if it will even make it to the next mile.

I always bought the fully specced high milage cars for useally atleast half to 1/3 of the price that they ask for the low milage ''bare'' models.

Of course my car (bmw😁) also has problems/needs regular maintainance, but if i compare it to the other people that post the same problems on different forums i am amazed that people useally have the problems i get for example at 200k miles which they report on their car with having 80k miles.

For example oil filter housing gasket, which is an o-ring between the oil filter housing to engine block, this is constantly being compressed and just stiffens by age/heat/cycles.
In my opinion this is more age/hours related then the miles, the part doesnt care if 1000 miles have been driven or 300k miles.

A car that does a 1hr commute everyday traveling 80 miles compared to the same car that does a 1 hour commute every day trying to get to the other side of the city and only covering 15 miles in traffic jams.

Both run an hour a day, after one year the first car will have 16.000 miles, the second car only 3000. However both have accumalated 200 hours.
After 10 years the first has 160k miles, the second one 30k miles. Both have 2000 hours. The one fetches a lot of money, the other is considered a money pit.

My personal experience is that the vehicles that travel a lot of miles useally have interiors that are like new compared to city cars which only do short trips, also people that use their cars to travel long distances useally are more keen on looking after it and are willing to spend more on maintance because the car/realiability is more important to them.

Comming back to the question, the car that spends the 1hr 80 miles on the highway each day will get their fluids/oil to operating temp which will vapour of the moisture in the oil and gasoline dilution.
The car that only does 15 miles 1hr each day will spend most of its time with a cold engine which prevents the oil from vapourising the moisture/fuel. Also people then generaly do not consider to change the oil because they think it only did 3000 miles anyway.

I am almost willing to bet that a lot of the engines that we see that are fully slugged up are short milage/slow driven cars.

Aircraft/helicopters, agriculteral machinery, generators, boats, dirtbikes, plant machinery etc... are all measured in hours for their maintenance so in my opinion it would be wise to do cars too for atleast fluid changes, things like tires/brakes etc.. are more milage dependend.
Engine hours in three distinct criteria for me.
1. November to February - city traffic and 1-2 500 mi trips - 120 hours. That equates to 3-4.000 km /2-2.5k mi. Long idling and short trips, lots of cold starts.
2. Normal driving with 1/3 of each - city, intercity (80-120kmh/50-75mph) and highway. Here I change at 150-170 hours which almost exactly equals 5k mi/8k km.
3. Highway, can go up to 200 hours, but actually never went past 210 h. and 9-10.000 km, it'll be either too hot, or I'll drive too fast for too long to push it past 200 hours.

My actual average speed seldom is above 30-40mph.

2017 Lincoln Continental 3.0EB.
I measure engine hours by simply reseting trip 1 at oil change. I never sit in the car without the engine running, so it's fairly accurate.

Another criteria would be if the engine noise, power and efficiency change at oil and air filter change. - sure sign, you do it too late.
For instance engines for RN17 oil (renault/Nissan 1.33tce) are prescribed for 30k km/20k mi... there's noticeable change at oil change at 10k km/6k mi... my colleague uses OE/Castrol/Ravenol all specified ar RN17 and OE air and oil filters. It's still noticeable. And he drives 95% out of town at 50 to 75 mph strictly, thus he's not putting more than 200 hours. Still it's noticeable.
Imagine what will happen at 20k mi OCI.
250 hours was what we used for vehicles on site. Should have been less after their efforts to cut costs.