Outboard tilt-trim oil provides rust protection for engines in the marine industry. For long periods of time, marine engines function under high loads and rotations per minute (RPMs), which causes automotive oils to break down and lose viscosity or ease of flow. For this reason, marine manufacturers produce manuals for owners of outboard motors which recommend specific oil types -- automotive oil with SAE 30 or SAE 10W30 specification, transmission fluid type F, Dextron Automatic Transmission Fluid (ATF) or power tilt trim fluid by OMC company. OMC is a manufacturer of marine engine manifolds, parts and gaskets.
SAE 10W30 Automotive Oil
A substitute for outboard tilt-trim oil is automotive oil with SAE 10W30 specification. For example, it is recommended that you use SAE 10W30 oil in older Mercruiser brand trim pumps. Amsoil brand SAE 10W-30 Formula Four-Stroke Synthetic Motor Oil can satisfy warranty requirements of four-stroke outboard motor manufacturers such as Bombardier/BRP, Evinrude, Honda, Johnson, Mercury, Nissan, Suzuki, Tohatsu and Yamaha. Use SAE 10W30 ouboard motor oil whenever an owner's manual specifies SAE 5W30, 10W30 or straight SAE 30. Mobil 1 brand 10W30 is also another option.
Transmission Fluid Type F
Transmission fluid type F is a substitute that can be used for outboard motor tilt-and-trim oil. Automatic transmission fluid has a high amount of detergent in it, so be sure to check your owner's manual.
Dextron ATF is a good substitute for outboard tilt and trim oil, especially since the tilt-trim unit is a hydraulic system. As a substitute, Penzoil company has a marine tilt-and-trim hydraulic fluid that can be used for power steering and tilt-and-trim systems. In addition, Penzoil has a marine outboard gear lube, though it recommends Penzoil ATF for Johnson and Evinrude electric shift models for 1972 and earlier and OMC Stern Drive models dated before 1977.
SAE 5W or 10W
Use SAE5W or SAE10W instead of quicksilver fluid for Mercruiser trim pumps. Other substitutes to quicksilver include chainsaw oil and sewing machine oil. Do not use automatic transmission fluid (ATF) for Mercruiser trim pumps, because the material used for the seals on its trim pump system is not compatible with either ATF or brake fluid.
In the 1970s, 30 weight nondetergent motor oil was used as a substitute for outboard motor tilt-and-trim oil.