As higher fuel prices push many of us to restrict our flying, I've found a product that may be worthy of considering to prevent corrosion in our engines. ASL CamGuard, http://www.aslcamguard.com/ , is a product that was developed to address this issue.
I don't have any interest in the product other than the potential for saving me from an early overhaul. I've used it in my three aircraft for the past two years and seen modest drops in wear metals. However, most important to me is preventing cam/lifter corrosion in my Lycoming engine. We all know that the camshaft location in our engine is not optimum in terms of assuring good lubrication. Long term storage can allow the cam to become pitted with rust.
I've changed from using Aeroshell 15-50 to Phillips 20-50 XC with CamGuard added. The net cost is almost identical, but I believe my engine benefits.
Your experience may vary, but this is the first product I've seen that may actually provide benefits to your engine. It is FAA certified for naturally aspirated certified aircraft engines.