All oil filter manufacturers make filters for the various private brand guys. Examples of filters made by others would include STP, Lee, Valvoline, Quaker State, Shell, Mobil 1, Bosch and Mopar. Champion Labs makes over 100 private label filters and more than a few original equipment (OEM) oil filters.

Most oil filters will filter out particles bigger than 25-30 microns. Some of the premium, more expensive filters like the Mobil 1 filter will filter anything bigger than 10 microns. This is where I would suggest you spend your money because a premium filter will make your engine last longer and your money is best spent, there.

The quality of each filter is measured a variety of ways, how much of the trash that's in the oil the filter will catch (efficiency), how much trash it will hold before it bypasses (capacity), the overall construction, the internal valving and their settings and if the filter has an anti drain back valve (needed if the filter is mounted at an angle, on it’s side or upside down) to prevent dry starts.

The bypass valve inside the filter simply opens or closes to allow oil flow. The bypass valve will sense a difference between the oil pressure in and the oil pressure out and if that difference in pressure is greater than 10-20 psi on domestic cars and 25-35 on import cars, the bypass valve will close off the filter and send the unfiltered oil on to the engine. Those numbers indicate that domestic car filters will bypass much sooner than many import filters.

Obviously, during a cold start, there will be a large difference in pressure between the oil pressure in and the oil pressure out after it has tried to get through the filter element. The viscosity of the oil, temperature of the oil, the quality of the filter element and the filter capacity and the engine temperature all determine how fast the oil filter can begin filtering oil on a cold start.