This is a question that pops up more than once every snowmobile season, so let’s delve deep into the pros and cons of running AMSOIL HP Marine Synthetic 2-Cycle Oil in snowmobile engines. AMSOIL exclusively recommends their Interceptor Synthetic 2-Stroke Oil for modern 2-cycle sleds in recreational use.

AMSOIL HP Marine Synthetic 2-Stroke OilWhy would one consider a boat oil for snowmobile use?

There are a couple of reasons why some snowmobilers may wonder about using HP Marine in their winter toys. The first reason is that some sled owners also have 2-stroke boat engines and wish to keep just one product around for both their marine and snowmobile applications. The second possible reason is that Interceptor costs just over a dollar per quart more than HP Marine and some budget-minded riders wish to explore this option.

What is the difference between AMSOIL HP Marine and Interceptor?

HP Marine is an “ashless’ two-stroke oil formula that is suitable for marine applications requiring the NMMA TC-W3 specification. “TC-W3” is an industry rating for outboard two-stroke oils. “Ashless” means that the detergent additives in the oil are non-metallic and will not create any ash deposits in the engine during combustion. HP Marine delivers superior performance in modern direct fuel-injected (DFI) models.

AMSOIL INTERCEPTOR Synthetic 2-Cycle OilInterceptor is AMSOIL’s offering for high performance, recreational two-stroke engines and is their most popular snowmobile oil. Interceptor is a “low ash” formula for applications requiring the API TC specification. This specification was developed for high output/high RPM two-cycle engines. “Low ash” detergent additives have metallic compounds which forms ash residue during combustion. This ash burns up and is evacuated through the exhaust stream. Interceptor is widely acclaimed for exceptionally clean performance in engines equipped with variable exhaust power valves.

The ashless and low-ash aspects of HP Marine and Interceptor are rarely discussed, but they are vital in drawing a distinction between the two products.

Ashless or Low ash- Why does this matter?

There is a critical justification for marine two-stroke engine needing ashless detergent additives and high performance two-stroke applications like snowmobiles (and some personal watercraft and motorcycles) requiring a low-ash formula. It all has to do with operating conditions.

Two-stroke outboards have much lower combustion temperatures than snowmobile engines. They also operate at lower RPM and see steady throttle positions for extended periods (think trolling). Outboard engines do not have variable exhaust power valves. Ashless formulas are required to prevent engine deposits and spark plug fouling. Low ash oils can create engine depositing and fouled spark plugs in outboard engines.

Snowmobiles engines are put under very heavy loads, have much higher combustion temperatures and experience widely variable RPM. Most all modern two-stroke snowmobiles engines utilize variable exhaust power valves. Low ash two-stroke oils excel under these conditions that will otherwise strain the limitations of some ashless formulas.

It is important to note that some snowmobile manufacturers strongly urge against using ashless or TC-W3 two-stroke oils in their engines. Ski-doo/BRP is especially vocal on this point.

Does this mean that HPM is a lower quality oil compared to Interceptor?

Not at all! It is simply designed to perform under entirely different operating conditions. In fact, AMSOIL does suggest that HP Marine can be used as a secondary option in some applications requiring an API TC (low ash) two-stroke oil. This is due to HP Marine’s high quality synthetic base oil and elite additive package. HP Marine is truly exceptional in its marine domain as it excels in the rigorous Evinrude E-TEC Lean-Mix setting field trial.

Interceptor is one of AMSOIL’s flagship products and is wildly successful in the snowmobile market. Despite its superb protection and performance in high-output two-strokes on dryland, like other low-ash two-stroke oils, it would not be suitable for the staid operating conditions of the average outboard engine. Excessive engine deposits and fouled plugs could be the result.

So the distinction is simple. Boat- use HP Marine. Snowmobile- use Interceptor.
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