Much like automotive engines, marine motors are becoming more advanced and tougher on oil. Four-stroke motors are becoming lighter and produce more low-end torque than before. They’ve largely closed the performance gap on two-stroke motors. In fact, sales of four-stroke motors are on the rise, while two-stroke sales have declined.
Demanding Operating Conditions
Marine motors are characterized by high-rpm operation that can shear the molecular structure of oil and reduce its ability to protect against wear. On average, a marine motor propelling a boat 30 mph operates at 5,000 rpm, while an automotive engine at 60 mph operates around 2,000 rpm. The added heat and stress invite wear and deposits. Heavy deposits can cause piston rings to stick. Stuck rings lead to compression loss, which reduces power. Stuck rings can also lead to catastrophic piston scuffing.
The marine operating environment creates additional challenges for oil. Marine motors are constantly exposed to humid air. The moisture the motor ingests increases the likelihood of corrosion compared to automotive engines. Water-cooled marine motors also run at lower temperatures than air-cooled engines, so moisture in the oil doesn’t evaporate as readily. Plus, when the motor is shut down for the day, moist air continues to enter the engine as it cools, increasing the risk for corrosion, especially if the oil doesn’t contain anti-corrosion inhibitors.
Marine-Specific Four-Stroke Formulations
AMSOIL 10W-30 and 10W-40 Synthetic Marine Engine Oil and new AMSOIL 25W-40 Synthetic-Blend Marine Engine Oil are shear-stable formulations that deliver maximum wear protection in four-stroke marine applications. They are formulated with advanced additives to guard against corrosion common to marine environments.
Marine-Specific Two-Stroke Formulations
AMSOIL synthetic two-stoke marine oils provide the same great benefits as always, including outstanding wear protection and low smoke. AMSOIL HP Marine® Synthetic 2-Stroke Oil is excellent in modern direct-fuel-injected (DFI) motors that generate increased heat and friction compared to their predecessors. It provides increased lubricity for reduced wear during normal and lean-mix operation. In field testing, HP Marine completely prevented piston skirt and cylinder bore scuffing (see
http://www.amsoil.com/proof for details).
AMSOIL Synthetic 2-Stroke Injector Oil protects against wear and piston scuffing while providing the added benefit of year-round use as a snowmobile oil.
For pre-mix applications, AMSOIL Outboard 100:1 Pre-Mix Synthetic 2-Stroke Oil contains a heavy dose of low-temperature dispersant additives that excel at reducing varnish, carbon and deposit formation in water-cooled motors. Its low-smoke, low-odor, low-toxicity properties produce fewer emissions at 100:1 mix ratios than oils mixed at 50:1, benefitting operators and the environment.
AMSOIL Synthetic Marine Gear Lube protects lower units from wear, even when contaminated with up to 10 percent water.