Dan, Let me explain why the anti-drain back valve filter or check valve as you call it is so important in the Bosch oil filter and other applications. I think you will better understand after this. Oil filters made for specific ( applications ) as in the De Lorean, we are a selected few. If your oil filter is pointing down like in most cars, then the filter is full of oil all the time, So when you start the car the filter doesn't have to fill up before oiling your engine. The De Lorean filter is mounted on the side of the engine and without the anti-drainback for check valve filter, you will be starting the car without oil in the filter so it will have to fill up the filter 1st before oil goes to the engine. Without the anti-drainback valve you will promote more wear to the engine because the filter won't hold oil because it will drain back to the level of the car and lubrication will be slower. If your running the recommended weight oil 20/50 or 20/40 I would want the oil there all the time to promote no wear during start up. This is also why PTE/Teflon was added to oil to help lessen the friction of metal from metal during that critical time of start up and running. This is like the fuel accumulator holding pressure in the gas system of the De Lorean. Without the constant pressure on the fuel system, then the cars would be harder to start. This also why you don't pump the gas pedal when starting the De Lorean. Sending units are cheap compared to the engine and I can't see companies spending millions of dollars designing an oil filter to such high specs just to hurt the engine. I will stick with Bosch, and other companies that make filters for the specific application. Anybody can roll up paper and put it in a screw on can and call it an oil filter and in certain applications it will work. Hey. Les. Remember the old days of oil filters. I hope this helps how important the oil filter is to the life of the engine. John Hervey www.specialTauto.com