Wow, you really have been saving up oil filter questions for 50 years, Randy. I'm glad you didn't wait another 10 years or I'd have to take over the Real Estate section to finish this answer.
The reason there are so many different filters is because engines are all different. And space is at a premium. Most engine compartments I work on these days have no room to spare. So when designing an engine, all the immovable parts are designed first. Then later in the process, they find a place for the filter, preferably right on the engine block. In order to fit oil filters into the nooks and crannies manufacturers ultimately allot for them, filters have to come in all different shapes and sizes.
Generally speaking, more expensive filters are better than cheap ones, because they use better filtration materials. Instead of plain old Charmin, filters now use materials like synthetic glass microfibers, which do a better job of filtering the oil. That's also why smaller filters can be used. With better filtration materials, they can provide all the filtration the engine needs in a smaller volume.
We tend to stick with OEM filters -- the filters made by the car's manufacturer. You can never go wrong with those. Modern filters also have check valves, which explains why the oil doesn't drain out of your Subaru filter, even though it's mounted upside-down. Without a check valve, the oil would drain out, and that would be a problem. If the oil drained out, every time you started your car, your oil pump first would have to fill the oil filter, leaving other parts under lubricated for those first few crucial seconds that the engine is running. But the check valve keeps the filter full and completely solves that problem.
So, basically, Randy, there's nothing to worry about. Stick with a Subaru filter or other quality brand, and you'll get all the filtration you need. I'll look forward to hearing from you in 50 years.
The engine motor oil is the lifeblood of your vehicle and the oil filter plays a vital role in keeping this oil clean and optimized to meet your engine’s performance needs. Oil left unfiltered for a period of time can become saturated with debris and harmful particles that can wear your oil pump’s machined components and damage the bearing surfaces in your engine. Without clean motor oil, your engine cannot perform at an optimum level.
The process starts with your engine motor oil passing through the oil pump, where the filter does its job of purifying the oil and pumps its back into the engine for reuse. This filtration system removes waste and captures all contaminants from your engine motor oil before pumping it back into your engine.
Since these filters are constantly running, they accumulate dirt and wear, making them less effective over time. This, in turn, hinders fuel flow and impairs your engine’s performance. The most common indicators of a worn or malfunctioning filtration system include reduced oil pressure, acceleration problems, and metallic noises under the hood.