I just read up on 3'000 to 5'00 mile intervals that might be prevalent in the US?

To me that sounds crazy. Many synthetic oils are officially approved to 15'000 miles.

Many synthetic oils _are_ fine that long.

Very few oil filters are fine that long. I know Mobil 1 makes one rated for 15k miles, but I'm not aware of any OEM components with near that lifetime.

Hopefully that changes soon, but in the meantime I'll keep changing the oil at the rate my oil filter is rated for.

oil change stores advocate 3000 miles. car manuals or cars with computers that tell you when to change the oil advocate much longer intervals.

Depends on use. My truck essily likes 4000-5000 mile oil changes. It runs noticeably worse towards the end of that mileage range. It works harder than most cars and produces a lot of power to boot.

It's possible that your filters are clogged or there is some source of contamination. You may want to buy and oil Catch Can. https://www.youtube.com/watch?v=T-B4VRxAtbw

Maybe, I also just drive it hard. I should get a secondary filter regardless.

It is true that a lot of synthetic oils are approved for 10, 15 and even 20,000 miles in some cases.

However, if you actually look at the oil after 10,000 miles it's usually very dark brown despite the high mileage rating so I personally get mine changed more frequently than recommended.

maybe it works fine when it is dark brown

Oil changes color as it captures contaminates such as soot, carbon deposits, etc. It can operate effectively while brown-ish, but if the oil is carrying too much it will blacken and start to thicken at which point it will be much less effective at lubricating your engine.

The shop I take our cars to recommends rotating the tires every 6,000 miles. Based on the oil life indicator in the car, the oil is getting about worn out by that point as well. Makes for an easy service trip to get both done at once.

Nowadays cars use an engine life monitor and report to the owner that they need service every 8-10,000 depending on use

Recently manufactured cars we own have those oil life monitors but some research shows they simply run down a milage count. The dealership even asks me what mileage I would like it set to. Sales pitch suggests that the vehicle is monitoring actual oil characteristics but in fact it is not.

What they do is calculate an oil lifetime based on running conditions of the engine. How long it's been on, what temperatures its running at, what RPM....

Point is that nobody should be changing their oil ever 3-5k.

My car tells me when to replace the oil. I don't even think about it, the amber light tells me when to do it.

They can and will with the correct supplies and parts (and handling).

There is a reason that some oils are far more expensive than others. Oil change shops have an incentive to make you come back soon, so you will be told there is no need for the more expensive oil. The composition of the oil and the quality of the engine and its parts will of course influence the build up of slug.