I read over 20 threads and they never really addressed the pros and cons using the older 400/426 filter in the newer 450's. IMO there are more Pros. Pros - It seem like they (the older 400/426 filter) would be the HOT set up for more number of oil changes (you can clean them a few times) and more FLOW for the motor. These things are only about $5.00. from Dennis Kirk. Cons - The older filter is 1 mm shorter and the rubber gaskets are a little different. Some people mention paper filters may filter finer particles. To this I say any particle this small will be suspended in the oil and get flushed out in our frequent (read obsessive) oil changes.