Motorhead Memo: The oil conspiracy

How about this as a way to cut your dependence on oil—foreign or otherwise: Choose your lubricant more carefully and quit changing it so often. I mean, by now we all should have figured out that the “every 3,000 miles” thing is marketing more than maintenance, right? Virtually no manufacturer recommends oil changing that frequently. Unless you’re some kind of conspiracy theorist, you gotta believe the recommended intervals come from actual testing by serious people who know what they’re doing. So why do we persist in wasting perfectly good oil all the time?

Extreme clean: Waste not, want not? Or just a waste?
As a kid, I rode two-stroke motorcycles, some dirt-oriented, but mostly street bikes. (They really don’t make ’em like that anymore!) One of the many things observed in those formative years of ring-dingin’ along, was that you never had to deal with dirty oil or changing same. It’s kind of a neat aspect of two-cycle design that engine oil is used only once—then it’s gone! (Too bad it went into the air we breathe, ’cause that ultimately ended the era of simple, dirty horsepower for all of us closet/cult “smoke riders,” but I digress.) This system worked in an engine designed with no recirculation of lubricant, no oil pressure, and full of ball, roller and needle bearings—putting out nearly twice the power and heat of similarly sized four-stroke engines of the day. I even remember a magazine comparison test of a Shovelhead dresser and a Suzuki GT-750 tourer, wherein the oil consumption of the two-stroke triple was less than that of the four stroke V-twin over a 2,000-mile ride! Though the topic of lubricant cleanliness between the two would make for a nice discussion on its own, it’s the consumption itself that’s the concern, since both machines were eating it up at similar rates and one was designed to use it once but the other was not! (About 600 miles per quart, as I recall.) A consumption rate near zero in current Twinkie engines serves to illustrate just how far our V-twins have come since back then. It’s us, the riders, who are lagging in technicality these days. Nowadays, it seems to me we still consume oil at about that 600 mile per quart rate in our engines—only it isn’t burned, it’s simply wasted in unnecessary changes. I guess old habits die hard (but not without reason, the state of the four-stroke art being what it was).

My first Harley was a 1957 Sportster. It had no oil filter, an oil pump created in the days of straight 50-weight, and a cast iron top end. It also ran a hell of lot stronger than most would think, even with its low, 7:1 compression and mild cams! The big deal then was getting my 100,000-mile pin from the factory. That’s right, a hundred grand on that old motorcycle—certified! How do you suppose that happened? You bet your butt: among other things, plenty of oil changes. Living with that lovable old relic (and keeping it alive) for so long, is probably why, to this day, I ignore “mileage intervals” for oil changes and simply check “condition” constantly. If the vital fluids look and smell dark, foul and less than vital they get changed—regardless of mileage! (Of course, it may also have to do with not ever having an odometer on that bike.) I also refused to run oils with molasses-thick viscosity (like 50w or 60w) in the thing! Multigrades may have made for more clatter and rumble in the bowels of the beast, even more heat radiating from within, but it never stuck, stunk or quit—and that was good enough to get me the mileage award—when seemingly every other old H-D out there was getting a top-end overhaul every 20,000 miles. I’ll bet a buck or two, when it was all saucered and blowed, I actually used less oil over the 100K than some folks do in half that many miles with “over-oiled” new machines. But at the time (and in that time) I learned a lot, much as I have in the 20-something years and additional 100,000 I’ve subsequently put on my Evo FXR. Mind you, even with its obvious advances over the ol’ Sporty, the FXR still has an oiling system conceived in the ’30s, vestiges of what passed for filtration in those days (like a tappet screen) and will fill the sump with oil if I let it set too long. Modern Twinkies have none of these “idiosyncrasies” and an extremely capable oil-filtration system, so exactly how often do you need to change your oil? It’s all well and good to see how engine technology has stretched out “required’ oil change intervals, but let’s also trace the arc of oil development and start piecing both parts of the puzzle together into a clearer picture. I think we’ll find that we swap oil so often largely out of habit, semi-credible wives tales, ignorance and fear for our motors, rather than any logical reason.

Is it the machine or the human that actually requires changes?
Modern motor oils can be justifiably considered miracles of technology, capable, for instance, of lubricating highly loaded bearings, revolving hundreds of times a second at temperatures in excess of boiling! Not to mention an almost uncanny ability to protect against a wide range of contaminants and wear agents. All the same, it would be inaccurate to say (or assume) that motor oils designed for modern engines are automatically superior in every way to oils of yesteryear.

From the day they figured out how to refine the stuff into lubricants, until this side of World War II, only “monograde” mineral oils were available and typical motorcycle viscosities were in the range of modern (so-called) SAE 40 to about SAE 60. Not much to choose from and not real great at what they did. In fact, racers used bean-based (castor) oils almost exclusively, because the stuff offered tremendous boundary layer lubrication under high-temp, high-effort conditions and loads. It also smelled real nice, but didn’t mix well with anything and would turn into sludgey crap given half a chance. No “shelf life” either—use it or lose it!

Back on the streets of the day, those heavy straight-weight oils had to be used for a number of reasons. For one thing, imperfectly cooled, long-stroke iron engines, with sloppy internal tolerances and bearing fit, would make short work (and a big joke) out of light-viscosity oil as soon as they got hot! Also pretty useless stuff when it came to bearing lubrication and oil control, whether past piston rings, valve guides or just plain leakage. That’s how Harleys, once upon a time, got so fond of thick oil. It was a time when you really did have to run a different weight/grade in summer than in winter and change whatever you ran at about 500-mile intervals. You see, the other old school aspect amounted to absolutely no help from “additives” in the oil to keep things in the engine clean. The owner had to do that cleaning via top-end “de-cokes” as they were called, which amounted to tearing the engine apart and literally scraping and scrubbing built-up carbon off the critical parts, by hand! Even after the Second World War, there were only a few anti-scuffing agents, anti-oxidants, and bearing corrosion inhibitors available, and still it was a dark art as much as technological advancement. This whole “additives” thing was in its infancy and as late as the ’50s, and on into the ’60s, people were still getting used to some new choices—like detergent or nondetergent and straight-weight (monograde), versus multigrade oils. As you can probably imagine, this was when things got tricky and people started forming opinions and taking sides on lubricants. Early multigrades weren’t always what they were cracked up to be and many an old-timer who’d never had problems with the old nondetergent monograde stuff he’d used forever, got bit (or blown up) pretty hard when he switched to the newfangled detergent-type multigrades.

Making the grade
Multigrade oils, by definition, have the characteristics of different SAE monogrades at different temperatures (a trick monogrades can’t perform at all—they are what they are). Say “cold” is 32 degrees and “hot” is 212 degrees. Straight 20W behaves like 20W hot or cold, so it’s too thin at high temperatures. Straight 50W or 60W might help when hot, but won’t circulate worth a damn unless hot, so cold-start wear is enormous. On the other hand, 20W/50 behaves like thin SAE 20W when cold and thicker SAE 50 once hot. (Although it’s still thinner in absolute terms when hot.) Make sense?

It’s worth stating a rule here: There is no technical reason why multigrade oil cannot be used in any motorcycle engine regardless of age or condition. The trick is to use the right viscosity range and figure whether it needs to be detergent or not. The reason this is true is basically because of the “hot” and “cold” characteristics of petroleum oils and the test the SAE (Society of American Engineers) has used since day one to determine viscosity.

It’s a sad fact, the SAE grading system has consisted solely of a check on the time taken for a measured volume of oil to flow under gravity through a small orifice in a piece of laboratory glassware known as a viscometer. Testing monograde oil this way is valid enough, but it’s pretty much accepted by oil experts that, to some extent, viscosity-improving additives in modern multigrades only serve to “fool” the test equipment. The flaw is, no account is taken of the viscosity improver thinning due to shear load. When multigrades were first introduced in 1951, the notion was that (for example) a 10W/30 would work in place of straight 30W. After all, it met 30W viscosity requirements in the viscometer tube! It didn’t quite work out that way and today we consider the (more or less) correct multigrade equivalent of 30W to be 20W/50.

Through thick and thinner
OK, so it’s easy enough to see that if 20W/50 is about the same as SAE 30 at “normal operating” temperature, with the added bonus of less viscosity when cold (for easier starts and quicker flow upon starting) something thicker in a multigrade would be needed to replace SAE 40, or 50W or even 60W. Oh, there’s 10W/40 galore for those who ride in colder climes, but all suppliers of 20W/50 will only recommend it for temps up to 100 degrees. That might not cut it in parts of the country where 100 degrees or more is “normal operating temperature” during the riding season—say Arizona, Nevada, Texas, Southern California deserts—places like that. You see, there are really two temperatures to be concerned with, the ambient temperatures of the area you ride in and engine temperatures, which in extremes, can get perilously close to thermal breakdown for the lubricant in air-cooled Harleys. This is a fact that flies in the face of current trends toward ever lighter “grades” of motor oil being forced on the industry by the need to cut fuel consumption in cars. This doesn’t bode well from the point of view of long-term engine wear. Time will tell. Harley ignores SAE ratings in favor of their own “360” rating, yet still sticks with accepted viscosity ranges. Curiously, the factory doesn’t have thicker multigrades, only the option of switching to their synthetic 20W/50. For those who prefer petroleum lubricants, the aftermarket does offer 25W/60, which will buy you protection to 110 degrees (or more) ambient air temperature. However, all this does is raise more questions, not provide answers.

What I’m getting at is this: Overly frequent oil changes are not the best defense against premature wear and tear and not just any old choice of viscosity is a guarantee either. In short, there’s more to this “proper lubrication” game than most of us realized. So how do you choose wisely? Next month we’ll talk about that, OK?