How do people choose oil filters for engines that dont specify a size?

Does each number Oil Filter size up go by a measurement or something.How do people choose oil filters for engines that dont specify a size?
I'm not sure if you're referring to the physical length, width and diameter or it's filtration capacity in microns.





First, any auto parts store can advise you of the exact factory replacement replacement physical size for your application. They also can cross reference physical size for extended lengths if there is room if that's what you're asking. It's important to remember not to change arbitrarily the sealing gasket diameter or weather or not if it has an anti-drain back valve.





If you've ever read or been interested in filtration capturing ability it can get confusing. I'm sure you've heard of the term: Micron filtering capacity. 1 micron = .000039 thousandths of one inch. In most automotive oil filter applications companies will actually advertise their micron filtration capacity. In other words: It's ability to capture a given micron size.





In this instance ';Moor's Law'; is not always better. On the surface you'd think a filter that captured the smallest size dirt particles it would be better. However, in automotive applications it's been determined that an oil filter that captures a particle size of 20 - 25 microns is adequate. It's been found that filtering below 20 microns will soon open the by-pass valve inside the filter and you get no filtration at all. This could happen well within 3,000 miles.





I'll admit to being an old woman when it comes to oil filter selection and physical size where ';Moor's Law'; is better What ever the application, larger filtration * surface area is always better. My ';thing'; is stick in the largest physical sized filter that you conviently can install which also meets the internal valving as required by the manufacturer.





A word to the wise. Don't be fooled by the physical size of the oil filter. Look inside and make sure the filtering media goes clear to the bottom of the can. If possible find out from the manufacturer how many square inches of filtering media there is in a given filter.





How do people choose oil filters for engines that dont specify a size?
There is a sticker under the hood called a catalyst. This should have a engine size and the year the car was made. If there is no sticker (catalyst) then count the spark plug wires and if there's four then you have a four cylinder. Go to the auto parts store and look up the year of your car and the four cylinder and you should get the right filter. You can also get the manufactures name and number off the filter already on the car and have the auto parts store cross reference that number to a number of the type they sell.
All engines have a specific size. There is a sticker under your hood that lists all the emission and engine size information. If for some reason the sticker is missing or cannot be read anymore, look at the v.i.n. number for the 8th digit. The 8th digit of the v.i.n. number is the engine code. You can take that number to any auto parts store, along with the year, make and model of your vehicle, and find out the correct engine size to determine correct oil filter application.
The identification of oil filters is arbitrary. When a new filter size or design is needed, they just add a number.


For years each maker had a set thread for the filter and a seating area for the gasket. Fords always use to take the F-1 filter, but with engine bays becoming smaller filters were needed to be made to fit into a specified place.


So in most cases it is not the engine size that determines the filter number but who made the car.
If all of the vehicles labeling is gone then you would call your cars dealership parts department and give them the VIN and they will tell you the size of the engine.
look at the 1 that,s on your car now and get the same 1 for your car. filters usually has a number on the filter.