Mercury 25W-50 4-Stroke Synthetic Marine Oil 25W50 oil is often recommended for engines used in racing. This high performance oil provides maximum lubrication for your marine engine. This oil maintains viscosity under the most extreme operating conditions such as Racing Operating engine at maximum output and high temperatures. Tow sports and fishing Alternating between periods of high RPMs and throttle down to low RPMs or idle. Protects against varnish buildup and sludge formation. Exceeds the r