Gerry Reid

Raleigh & Zebulon, NC

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Synthetic oil can make your engine nearly immortal, but all engines will ultimately die, Weigh all the factors to see if it makes sense for your engine.


November—December 1999 one on the use of synthetic lubricants. Most questions were concerned with the bypass filtration system and whether it made sense to change an engine with several thousand mites on it to synthetic oil. By now most people have read enough material on the improved lubricating qualities of synthetic oil and are wondering if it would be good for them to make the switch. Some writers— and, of course, the consultants at the synthetic oil companies—would say “Sure. Go ahead.”  I’m not so sure that’s true in all cases, Let’s look at a few of the considerations.

There are at least three types of engines we’re using: gasoline, lightweight diesel and heavy diesel. Given good maintenance, gasoline engines should last for about 175,000 miles, with a few lucky ones going to a bit more. That means the engine is usually about half gone at 80,000 miles. Does it pay to change a gasoline engine with 70,000 to 80,000 miles to synthetic oil? Would you be satisfied with driving an 80,000-mile engine for, say, another 200,000 miles? That’s what it amounts to. Changing an engine fromconventional oil to synthetic oil radically reduces wear, but it doesn’t stop wear. The engine is still going to wear out. It just takes longer with synthetic oil.

There’s also the problem of engine accessories. Gasoline engines, even the very best of them, are considered to be throwaway engines. Ignition systems, water and fuel pumps, gaskets, cooling systems, fuel-injection systems and wiring systems are all built with the expectation of being discarded somewhere around 150,000 to 200,000 miles, Further, depending on its construction, even a gasoline engine is subject to the diesel engine nemesis, cavitation erosion. Under normal conditions it isn’t a problem with gasoline engines, because we expect them to quit at less than 200,000 miles and no one even talks about treating coolant water in a gasoline engine to inhibit cavitation erosion.

But, if you’re going to improve the lubrication with the expectation of getting 300,000 or more miles from your gasoline engine, you have to consider cavitation erosion as a factor. That means treating the coolant with DCA from your big-truck dealer. It also means changing the coolant at least every two years with distilled water. Do you really want all that hassle with an engine that’s going to need a new water pump, several fuel pumps, several new ignition wiring systems, etc.? Only you can answer that.

The second type of engine we’re using is the lightweight diesel engine for Ford motorhomes and Chevy! GMC and Ford pickups and vans,  These are built somewhat heavier than the corresponding gasoline engines, and given reasonable care they should last significantly longer. It’s not unusual for one of these engines to run for 300,000 miles with conventional oil. But when my Ford diesel took a permanent vacation at 105,000 miles, the Ford ‘customer satisfaction” guy asked, “What did you expect?” Apparently, Ford sees these engines as being replaced at around 150,000 to 200,000 miles.

One very important factor in getting long mileage from all diesel engines is the regular, routine testing of the coolant and treatment with DCA. Regardless of what your dealer or the “guy down at the courthouse” says, if you don’t treat the water, you’ll he visited by cavitation erosion sooner or later. The bill will be the cost of a new engine. So let’s assume that you’ve got a lightweight diesel with 150,000 miles on it and have been routinely using DCA. If you change to synthetic oil and are lucky, you can expect another 150,000 miles. But you’ll still be driving a 150,000-mile engine and you’ll still have to took at replacement injectors and tuepumps. Does it pay?  Probably. Who knows?  You may even get really lucky and see the odometer hit 400,000 miles and get some real bragging rights.

Change the scene to start with an engine that has 70,000 to 100,000 miles or less, and changing to synthetic oil makes a lot of sense.

The third type of engine is the heavy-duty diesel made by Cummins, Caterpillar and International, These engines are built much heavier than the other two types and are intended to go for 700,000 to 1,000,000 miles before overhaul. There  will be occasional replacement of such components as fuel pumps and injectors, water pumps and radiators, hut even these components ate built of much heavier construction than their cousins in gasoline and light-duty diesel engines. Does it pay to change one of these engines with 500,000 miles to synthetic oil? If the engine is running as it should be and showing no heavy use of oil—anything under a quart per 1,000 miles��� I’d say yes, without hesitation.

When I bought myInternational 9200, ‘Big Red,” it had 550,000 miles on the odometer. It was using very little oil, was running good and appeared to be able to last for another 200,000 miles before needing an overhaul. I changed to Amsoil synthetic 15W40 at 560,000 miles and installed anAmsoil bypass filtration system.  Oil consumption didn’t change. I expect the engine to last for another 400,000 miles. One feature that frequently gets overlooked with these engines is that they can usually be completely overhauled to virtually new engine status for around $6,000, sometimes less.

Two other frequently asked questions, were what does a bypass filtration system do and why install one? You don’t have to install a bypass filter. The choice is yours. With a gasoline or lightweight diesel engine, you could easily change to synthetic oil with the present filtration system and just change oil every 20,000 to 25.000 miles, assuming you’re using Amsoil diesel 15W40 or something comparable. But that means you’re laced with disposing of several quarts of dirty oil every oil change. Oil changes can be safely eliminated with a bypass filtration system. To me, that’s a big advantage, and with larger diesels it becomes almost essential because of the quantities of oil they require.

One letter writer argued that even the lull-flow filters presently used have a bypass feature. Why install a new bypass system? Whoa, there. The bypass valve in a full-flow filter is there to avoid the catastrophe that would occur if the filter became clogged and didn’t permit oil to flow to the engine bearings. Bypass on a full-flow filter means no filtration at all. That’s no good. A bypass filtration system is used in addition to the fullflow filter. As the oil circulates through the engine, a small amount is continually bled off the main line and sent through the bypass filter, full-flow filters remove particles larger than 20 microns. The small stuff continues to circulate. A bypass filter removes particles down to 5 microns, sometimes even smaller. This takes out virtually all the wear-size particles, and its use is essential if you want to eliminate oil changes.

With the bypass filter system, you still replace the full- flow filter at normal intervals, usually 10,000 miles. Replace the bypass filters when needed. How can you tell when the bypass filter needs to be changed? The kid in the front row has the answer. The touch test. If oil is circulating through the bypass filter, it’ll be warm.   When you first install a by-pass filter use the touch test when the engine is warm after running for an hour and form a mental image of how warn, the filter is. That’s your test. When the filter is no longer that warm after an hour or so, change the filter. That will usually be around 15,000 miles or more.

Another essential element for eliminating oil changes is routine analysis. Draw off a sample every 19,000 to 20,000 miles and send it off for analysis. The laboratory will test it for all the normal wear particles plus a bunch of stuff you never expected to he in your oil, and the lab report will tell you whether the oil and/or filters need to be changed. Pick a lab and stay with it, because the technicians there will build a computer record for your engine. You can buy analysis service from Amsoil or most large-diesel-engine dealers.

A final question raised by several letter writers was when to start using synthetics. It all depends. In a light-diesel or gasoline engine, I’d start with the first oil change. By that time the pistons and cylinder walls should have become friendly. or “broken in.” Changing to synthetic oil at that time will keep the pistons, cylinder walls and bearings in nearly new condition for a long, long time.

With heavy diesels the answer isn’t quite so simple. Some are so finely matched at the factory that little break-in is  necessary; with others it takes longer. One new diesel I had used a lot of oil for the first 8,000  miles or so then quit. By 10,000 oil miles consumption was down to nearly zero. I’ve had diesel drivers say that it took their engines 30,000 miles to break in. So when do you make the switch? If the new engine isn’t using oil at 10,000. miles, usually the factory- recommended interval, change to synthetics. If the engine is still using oil, wait until oil consumption drops off and then make the change to synthetics. If the engine is still using a quart or more per 1,000 miles at 30,000 miles, take it back to the dealer and file a complaint.

Coast to Coast Magazine  April, 2000


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