Tag Archive for: outboard engine

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Which AMSOIL 2-Stroke Pre-Mix Oil For Mercury Outboard Engine?

A reader asks: I am looking for some input on outboard 2-stroke oil selection. Having reviewed all the product literature from AMSOIL, it seems that I have three choices, but I cannot determine which is best suited from my motor. My engine is a Mercury Outboard 90 hp, and my choices seem to be: (i) Synthetic 2-Stroke Injection Oil (AIO), (ii) HP Marine Synthetic 2-Stroke Oil (HPM) and (iii) Outboard 100:1 Pre-Mix Synthetic 2-Stroke Oil (ATO). I pre-mix my fuel at 50:1. The outboard is carbureted. The original oil spec recommended by Mercury was TC-W.

Our answer: There is not a wrong choice between those three products for your engine. Any one of these products would be a fantastic upgrade. But let’s narrow it down.

“HPM” HP Marine

AMSOIL HP Marine Synthetic 2-Stroke OilAMSOIL HP Marine Synthetic 2-Stroke Oil (HPM) would be the ultra-premium choice. This sophisticated formula pulls out all the stops providing exceptional wear control and world-class deposit prevention. HP Marine also offers some quality features that are specific to marine applications. It has an anti-rust/corrosion package which provides engine protection both in and out of season. It also delivers very clean emissions and low aquatic toxicity. For engines that require premix, mix HP Marine at a 50:1 ratio.

“ATO” Outboard Synthetic 2-Stroke Pre-Mix Oil

Outboard Synthetic 2-Stroke Pre-Mix OilAlso very much a premium choice, “ATO” Outboard Synthetic 2-Stroke Pre-Mix Oil is AMSOIL’s dedicated oil for pre-mix only. This highly concentrated pre-mix oil that is designed to safely be mixed at ratios of 100:1. Outboard 2-Stroke Oil offers clean operation, low smoke/odor, low aquatic toxicity and optimum throttle response. Despite the proven 100:1 mix ratio, ATO Outboard makes absolutely no compromises in terms of wear control. It also contains a powerful anti-rust ingredient to keep engine internals pristine all year long.

“AIO” Synthetic 2-Stroke Injector Oil

AMSOIL Synthetic 2-Stroke Injector OilAMSOIL Synthetic 2-Stroke Injector Oil (AIO) is a fantastic synthetic 2-stroke oil option with a moderate price tag. Despite being called an “injector oil”, it is designed for flawless operation when used as a premix at 50:1. AIO also delivers the features one expects from a good synthetic oil such as improved performance, excellent wear control and low smoke. Also quite suitable for snowmobiles, ice augers and two-stroke-powered yard tools.

To sum up, all of the mentioned products would work extremely well in your engine. The premium options would be HP Marine and ATO Outboard Synthetic 2-Stroke Pre-Mix Oil. A budget-priced alternative is AIO Synthetic 2-Stroke Injector Oil. AIO is still an upgrade over the vast majority of synthetic 2-stroke oils on the market. It really comes down to the price and a few nuanced differences in these products.

Contact us using the form on this page for prices and questions.

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Is AMSOIL Interceptor Suitable for Outboard Engines?

A Reader Asks: I use AMSOIL Interceptor 2-Stroke Oil in my snowmobile and I’m wondering if it can be used in our older Mercury outboard engine?

AMSOIL INTERCEPTOR Synthetic 2-Cycle Oil

AMSOIL Interceptor is ideal for snowmobiles, but not suitable for outboard engines.

Answer: The short answer is no. AMSOIL Interceptor Synthetic 2-Stroke Oil is the best possible choice for your snowmobile, but it is not appropriate for your outboard engine. While both your boat and snowmobile have 2-cycle engines, it is easy for many to assume that any 2-stroke oil is cross-compatible. This is not the case as notably different 2-stroke oil chemistry is required for each application.

The water cooling, relatively low RPM and tame tuning of outboard engines means that combustion chamber temperatures of your outboard are drastically lower than the internal operating temps in your snowmobile engine.

Because of this difference, outboard engines require a two-stroke oil with the NMMA TC-W3 designation. TC-W3 oils have “ashless” detergents that keep the combustion chambers, exhaust ports and spark tips clean. Ashless oils are designed to prevent deposit build-up and spark plug fouling in the outboard engines.

Your snowmobile requires a “low-ash” two-stroke oil which is usually identified by the API TC specification. Low-ash detergents form a trace amount of ash deposit upon combustion that is promptly ushered out of the exhaust pipe. Low-ash detergents do an outstanding job of keeping the combustion chambers, variable exhaust power valves and spark plug tips clean in hot-running, high strung snowmobile engines.

Using a low-ash 2-stroke oil formula in your outboard would be inviting deposit build-up in your exhaust ports and potentially fouled plugs. Over time, this is a recipe for very poor performance.

Conversely, ashless 2-stroke oils for outboard engines are ill-equipped for the high-heat, high RPM existence of snowmobile engines. Ashless TC-W3 marine 2-stroke oils are optimum for outboard engines, but will form very troublesome deposits in snowmobile engines.

Here are some better AMSOIL 2-stroke options for your outboard engines.

HP Marine Synthetic 2-Stroke Oil- AMSOIL’s elite offering for NMMA TC-W3 applications. An appropriate product for the latest DFI outboards or older engines. Can be used in oil injection systems or as a premix.

AIO Injector Synthetic 2-Stroke Oil- AMSOIL’s entry level synthetic oil that is ideal for older outboards with oil injection or premix.

Saber Outboard Synthetic 2-Stroke Premix- An ashless 2-cycle oil for premix applications only.

Questions? Contact us using the form on this page or call us at 1-800-748-5781.

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