Preventative Maintenance

As you all know here, there is a huge range of what people know, believe and recommend when it comes to vehicle maintenance.
Some swear by the 3k/3 month oil change. Some say brake fluid never needs replacing, only topping off. Some say do a tranny flush every 5 years. Some say do what the manufacturer recommends. Some say 15k/ 12 month oil changes are fine.
It is a constant cause of confusion to consumers and a constant cause of frustration to technicians.

My question is this, and for now, only those with formal automotive educations.

Where did you learn what you know about preventative maintenance, and do you make recommendations that differ from the manufacture of the vehicle?

For you that do make recommendations outside what the manufacturer recommends, what are some of them and why?

Thanks

Interesting subject.
Most auto maintenance is a trade-off of cost vs. utility. Many components, such as brakes, tires, engine oil etc slowly deteriorate. They will continue to function when they get worn, but not as well as new components. So, one needs to make a decision as to when the benefit of the new components outweighs the cost of installation. .

Auto manufacturers sometimes extend service intervals for marketing reasons. A buyer might find one car is "cheaper to run" because the recommended oil change interval is every 6000 miles, instead of 3000 miles.

But what if both engines have the same wear issues? The engine with 3000 mile oil changes may last longer than the 6000 mile interval, so the more 'expensive' car will end up lasting longer.

Another issue? The type of use the car gets. Lots of short trips and lots of city driving is harder on a car, per hour of use, than highway driving. So a city car should get more maintenance per mile than a highway car. But this is not always included in maintenance intervals.

So, experienced drivers rely on their awareness of vehicle use, vehicle systems and condition to arrive at a reasonable maintenance interval. Also, at least for oil changes, many cars have oil-life indicators, that monitors inputs like number of cold starts, hours of use, mileage etc to arrive at a recommendation for when an oil change should be done.