Harry,
Most synthetics are compatible with oetrolium products, and I can assure you the Amsoil is very compatible with petrolium, so there would be no ill effects after using the Amsoil. However, I would think after you tried it, you would like it.
Just my opinion on the last statement.
wayne
amsoilman
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94'SLT 4X4 AT/White in color. Factory Tow Hooks & Running Boards. Amsoil By-Pass filter, Amsoil Air cleaner,and all fluids are Amsoil. Optima "Red Top" batteries.
BD exhaust Brake, BD Torque Lock, BD Torque Converter, Dr. Performance Stage II Injection Pump. Mag-Hytec Diff Cover,Mag-Hytec Transmission Pan, Isspro Pyro, Boost,Oil temp Gauges mounted in 3 Gauge post mount. One gauge monitors Engine Oil, Trans, Diff. Temps.