If you’ve ever owned a Ski-Doo E-TEC you were likely really surprised at how little oil the engine was consuming over the course of a day or even a week’s riding.
I remember my first experience with a low-emissions 2-stroke the first time I rode it. I checked the oil tank and started to panic. “Surely, I’m going to ruin this engine. Something must be wrong with the oil pump – or an oil line must be blocked – because it just isn’t using enough oil at all.”
The fact is 2-stroke oil is a pretty amazing substance, sticks like glue to wear surfaces and mixes with gasoline very uniformly and rapidly.
In pre-mix situations you can go as high as 100 to one gas-to-oil ratio with some oils and not damage your engine. Seems almost ridiculous!
With Semi-Direct and Direct Injection engines there’s very little gasoline introduced into the crankcase – in some cases, none. As a matter of fact, an E-TEC engine’s crankcase is pretty much sealed-off from the engine’s combustion chambers when it’s running and there’s only fresh, clean air allowed by the throttle bodies into the bottom end which is immediately transferred via transfer ports to the top of the engine.
This is one of the reasons the engine uses so little oil: When there’s no gasoline washing down or diluting the oil going to the crankshaft and rod bearings every stroke, the lube stays on those bearings way longer.
With an E-TEC engine or a Polaris Cleanfire SDI, the oil is “pin-point” injected in minute proportions directly onto those bearing surfaces. Piston rings and wrist pin lube is also delivered by the oil pump.
The point is, very little oil is needed on those engine parts because gas isn’t mixing with the oil and washing it off the bearings and up the transfers. As a result you don’t use as much oil as the old days of carburetors and mechanical oil pumps.
Less oil consumption makes a great case for the newest electronic oil pump technology that links up with the sled’s ECU to determine how much oil is demanded by the engine at whatever particular RPM it’s running.
These new “smart” oil pumps are a big part of the reason the newest-gen 2-strokes can run so oil lean.