Lots of these. E.g. changing car engine oil every 20 minutes. Although this doesn't extend to the US government -- the army periodically samples oil and changes when it actually needs to be changed.
In the US, I’ve always heard something like every 3 months or 3,000 to 5,000 miles. The cars even warn you in that timeframe.
In Europe, a mechanic was very confused when I talked about an oil change when one was done the prior year. He said it’s more every 2 years or 20,000 to 25,000 kilometers. Once again the cars were set up to warn at that distance.
I’d love to get to the bottom of it. Why such a difference? I can understand the garages wanting the extra business, but why would the car manufacturers go with it?
1) Opportunity to upsell other services,
2) Some people (quite a lot, actually) have alien-to-me car buying habits and might be convinced to trade in their new car after only a year or two and buy another new one if you can just get them into the dealer at the right time.
No clue if that’s why they do it, but maybe.
There is also the case of changing oil for hot and cold seasons- getting thinner oil in the winter and thicker in warmer weather to adjust. I think thats more or less a thing of the past as well, my Honda does not specify/recommend this in the owners manual but perhaps some cars do?
Old adages sometimes stick around forever though- especially when there is money to be made in keeping them alive.
Specifically, transmission fluid is often considered 'lifetime' fluid that doesn't need to be changed, and, if you follow that advice, you end up replacing the transmission, an expensive endeavor, whereas if you don't, you can typically double its usable lifetime.
You also have to be careful about engine oil, because the margin of error is very small. Most modern cars have an oil minder, and those work well provided the oil itself is in spec.
Don't forget to make your swap space double the size of your ram!
Those extremely long intervals will only work for cars that travel long distances, where the engine has a chance to warm-up and burn off any residual gasoline that gets in the oil during cold starts. If said car spends most of its life in a city, doing short trips, the oil gets rapidly dilluted and loses the ability to lubricate the engine properly.
Most modern cars will take all this into account when trying to determine when the next oil change is due. Also, manufacturers nowadays usually specify shorter intervals (6 months or 7500km) for modern direct injection engines that only drive in a city.