|A Hot Idea|
This proven, simple, low-cost item can reduce engine wear, emissions, and hard-starting.
By Richard Thiel — January 2003
If someone told you that you could reduce your diesel’s wear rates by as much as 30 percent at a modest cost, would you be interested? Chances are you would, if you planned to keep your boat more than a year. Well, there is a way, and it’s been proven in thousands of over-the-road trucks, where engine longevity can be a matter of economic survival.
The key to this savings is the fact that by far the highest engine-wear rates occur at cold start-up. When you shut down your engine, lubricating oil on crucial parts immediately begins draining into the crankcase. Although some oil will remain on surfaces almost indefinitely, it’s a considerably thinner film than is present when the engine is constantly pumping fresh oil throughout the system.
Moreover, engine tolerances are specified by engineers to allow for expansion due to heat, so a cold engine will be “looser” than a warm one, creating the potential for more lubrication deficiencies.
Then there’s viscosity. We all know that a cold liquid is usually thicker and thus more resistant to flowing than a warm one. Most engine oils today are “multiviscosity,” identified by numbers such as 10W-40, which means the oil has the viscosity of a 40-weight oil (thick) when it’s hot and a 10-weight oil (thin) when it’s cold. Still, if you pull a dipstick on a cold engine and hold it at arm’s length, you’ll see it takes a lot longer for a drop of oil—even multiviscosity oil—to form and fall off than with warm oil. That’s why when you cold-start a diesel, it takes longer for the cold oil to reach all the engine components, particularly if it must travel through tiny passages. Thick oil is simply a lot harder to pump.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.