An engine’s need for the best possible lubrication is obvious, but these days everybody wants to extend the oil-drain period as long as they can. Trouble is, the
lube’s critically important additive package breaks down over time, which puts a lot of pressure on your engine’s oil-filtration system. Depending on the engine maker and a bunch of conditions, you can indeed go way beyond the ordinary 15,000-mile oil-change period, but carefully.

One of those conditions is the kind of filtration you use to keep your oil clean, though you should know that filters don’t work alone. Some additives in the lube are there to catch contaminants and keep them in suspension until drain time. Oil is ready to change when it can’t hold any more crud.

There are several filter types from many manufacturers, so which one should you choose?

Filtration Basics
Basically, a filter is just a metal can with some filtering media inside to catch contaminants, both organic (mostly bacteria that forms sludge) and inorganic (dirt and worn bearing metal). Of course it’s not that simple.

Primary filters nab big particles in the 25- to 30-micron range (a hair on your head is at least twice that thick, by the way) while secondary filters go down to 5 or 10 microns.

Primary filters are known as ‘full-flow’ types because all the engine oil runs through them. They let smaller contaminants go because you don’t want to restrict the flow of oil through them. Some are designed expressly for long drain periods.

Secondary, or bypass, filters don’t take all the oil at the same time – in order to maintain flow – but they’re much more efficient than primaries. They can be retrofitted quite simply if your truck didn’t come equipped that way. Usually, they’re installed beside or near the primary filter, but they can be mounted remotely.

Does every engine have or need both? Not necessarily. In some cases – smaller engines doing light service in clean conditions with frequent oil changes – a primary filter is enough. The tougher the work and/or the working environment, the greater the need for a bypass filter. Check with your engine maker to determine your needs.

Bypass Filters
In broad terms, there are four basic bypass types, though at least one
manufacturer has developed a single filter that combines both bypass and full-flow functions into one canister. Filtration development certainly hasn’t stopped, and as the pressure on engine lube increases with the onslaught of environmental demands, we’ll surely see more innovations over time.

The basic types are:

Spin-ons, using various natural or man-made media. They look like ordinary full-flow types.

Thermal chamber types filter the oil but also heat it to boil contaminants away, thus ‘re-refining’ the oil.

Centrifugal filters, powered by the truck’s air system, spin dirt out and collect it in a container, which must be cleaned out regularly.

Stationary canisters, again with varying filter media. Their advantage is that they hold a gallon of oil, sometimes more.

Choosing the right one is best accomplished by consulting your engine maker, reading whatever manufacturer’s literature you can get your hands on, and asking other people about their experience. Keep in mind that all of them demand some level of maintenance and that not all them are intended for extended drain intervals. Most importantly perhaps, ask if the filter maker’s warranty will cover
engine damage in the event of some failure.

Oil Analysis
A lot of truckers, fleets and owner-operators alike, swear by the benefits of oil analysis when it comes to deciding on an ideal oil-drain interval. Like a blood test that reveals a lot about your physical health, the analysis of used motor oil tells a great deal about the condition and performance of an engine. It might even tell you that you shouldn’t extend your drain intervals but actually reduce them.

Conducted routinely as part of a total preventive-maintenance program, oil analysis guards the health of an engine, detecting evidence of trouble before serious harm is done. Very sophisticated instruments are used to test for the presence of liquid and solid contaminants. Solid contaminants might include dirt and sand, fuel, soot and wear metals including aluminum, chromium, copper, iron, lead, silver and tin. Such trace metals indicate excessive engine component wear, but all these little particles can represent a threat.

You need at least two oil samples, collected at the time of regularly-scheduled oil and filter changes, to determine if you can extend your drain interval. If the analysis shows all is well, you would likely start extending the interval in increments of 5000 miles – as long as you have the oil analyzed after each additional 5000 miles. You
can keep adding to the interval until the analysis starts to show trace metal readings.

Remember that your choice of both filtration and drain interval could easily affect your engine’s warranty, so this isn’t a place for a lot of solitary experimentation.
Engine makers are keenly aware that truckers of every size and stripe are trying hard to keep costs down, so they’ll work with you to establish what’s right for your truck in your operation.

Rolf Lockwood is editor emeritus of Today's Trucking and a regular contributor to Trucknews.com.

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