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Time to Embrace the New Generation of Lightweight Engine Oils

For those of you who have seen more growing seasons than you care to admit, few things today are the same in farming. Procedures that 20 years ago were considered the norm are now relegated to nostalgia. Long gone are the days of moldboard plowing, walking the beans, cultivating between the rows, and high-viscosity (thick) engine oil. As accepted as the modern agronomic practices are, so is the need to embrace the new engine oil theories. 

In the same way that switching from conventional tillage to no-till involves much more than adding a set of coulters to the planter, the evolution that brought about the newer oils encompasses many factors. It wasn’t that the oil companies decided to make lower viscosity oils and the engine manufacturers agreed by changing the decal on the oil fill cap. Quite the contrary.

Manufacturers drive the product that oil companies produce. In the past, it was necessary to have high-viscosity oil since the technology and chemistry were not in place to create a lubricant that could deliver the desired results with a lower viscosity. Today, that has all changed.

Some new diesels specify 5W-30 oil, a viscosity my father would not have even used in a lawn mower. The industry has found ways to add performance without increasing viscosity. In addition, newer engines place higher demands on engine oil with increased power per cubic inch, high temperature emission control strategies, and the need to extend service intervals. The new oils deliver on all of this.

When designing an engine, the goal is to have the tightest clearances possible for the most exact fit of critical parts. 

The challenge is to get oil to these areas quickly on initial start-up. Excessive wear occurs during the transition from crank to run. This is especially true with overhead camshaft engines since the majority of the valvetrain is as far from the oil sump as possible. With oil’s propensity not to flow when cold, this becomes an issue. Over the course of the life of the engine, it will experience countless cold and, thus, dry (no lubrication) starts; each one slightly degrades life expectancy.

The way to get the oil quickly to all of the engine parts is to use a lower viscosity grade but one that can withstand the pressures of the engine under load.

Once the oil industry was able to produce a lightweight oil, other benefits were realized beyond cold flow. Two benefits were increased fuel economy due to a reduction in engine friction and the ability to decrease machining tolerances. 

Every engine experiences energy loss in three areas: thermal (heat into the coolant and out the exhaust); pumping (the work to fill and empty the cylinder); and frictional (the energy to turn the crankshaft, camshaft, oil and water pumps). 

It is accepted that each area consumes approximately 25% of the potential energy from the fuel used, thus, only 25% of the Btu in the fuel do any work. Lower viscosity oils are able to decrease the frictional losses in the engine, and that is how they improve fuel economy.

Tighter clearances result in a quieter and long-lasting engine along with a reduction in emissions when referencing the piston-to-cylinder wall clearance and ring end gaps. 

Low-viscosity oil required a rethinking of the inherent slight taper that is created in the connecting rod bearings along with the finish on the cylinder wall. Current engines usually employ a cylinder wall finish that is called plateau honing. The wider bearing clearances that were required with old-style oil created a nonuniform oil film between the bearing surface and the connecting rod or crankshaft journal.

The decreased bearing clearances allowed with the new oil actually result in a more uniform oil wedge between the journal and bearing surface. This greatly improves potential engine life. 

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