In a press release on June 10th, Mobil announced that it had decided to permanently withdraw its AV-1 fully synthetic oil from the market, and was recalling existing stocks of AV-1 from its distributors.
In recent months, both Mobil and TCM became aware of a number of cases in which severe deposits of lead sludge were discovered in big-bore Continental engines that had been operated on AV-1. As a result of these reports, TCM decided to remove Mobil AV-1 from its list of approved oils. Mobil then decided to withdraw the product from the market altogether.
So What Should I Do Now?
We recommend the following procedure when discontinuing the use of Mobil AV-1:
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Fly the airplane for at least 15 minutes to bring the oil fully up to operating temperature and to agitate any sludge into suspension. If you have a constant-speed propeller, deep-cycle the prop control several times both before and after the flight in order to de-sludge the propeller hub.
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Drain the oil as quickly as possible after the warm-up flight to insure that contaminants are drained from the sump before they have time to settle out of suspension.
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Change the oil filter or clean the oil screen.
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Service the engine with a 100% petroleum-based AD oil such as Aeroshell W (single-weight) or Phillips X/C (multi-weight). Petroleum-based oil has the greatest capacity for scavenging any lead deposits that may have been left by the AV-1 and holding them in suspension.
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Drain this oil after 10 to 20 hours of operation. It is likely to be dirtier than usual, having scavenged any deposits left by the AV-1.
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Change the oil filter or clean the oil screen.
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Service the engine with whatever oil you intend to use on a regular basis. The CPA Tech Center generally suggests using a single-grade petroleum oil such as Aeroshell W 100 for optimum protection against corrosion. For cold weather operation, a multi-viscosity oil such as Aeroshell 15W-50 or Phillips X/C 20W-50 may be used.
