Airframe and Powerplant

Do they or don't they (work)?

Controversy surrounds oil additives like a San Francisco fog. Major oil company engineers pooh-pooh additives, calling them a waste of money and potentially damaging to engines and bank accounts. Additive makers call the oil producers ultra-conservatives who merely want to protect product image. Some aircraft operators claim clear and present success with certain additives, while other owners suggest the advantages are nonexistent or so slight as to be random occurrences.

Where, then, is the middle ground? It depends upon the particular additive, what you expect from it, and, frankly, the condition of the engine using the additive. What's more, overall maintenance practices and operating techniques, including frequency of use, all influence how oil behaves inside an engine.

One thing is clear, though. No mechanic in a can or even the most expensive, top-grade lubricant will fix a mangled engine. Spalled lifters, lopped-off cam lobes, broken rings, out-of-tolerance valves and guides — none of these will suddenly return to as-new condition upon receiving the supposedly restorative salve of an oil additive. If you have high oil consumption, low compression, leaks, or other forms of firewall-forward mayhem, treat the problem rather than the symptom.

For engines in good condition, there may well be some advantages locked in those additive cans. But first you must understand what an oil additive can and cannot do for your engine. Unless there's something already wrong, like fouled plugs or leaky rings, additives will not provide more power. Thrust at the prop comes, naturally, from explosions inside the combustion chamber. Assuming the correct mixture of fuel and air is present, that the spark to ignite the combo arrives with sufficient strength and at the right time, and that there are no valve train or bottom-end anomalies, an engine will make only so much power for a certain state of tune. Naturally, leaking valves or poor ring sealing will result in a lower compression ratio or poor combustion-chamber breathing, which will reduce available power. If an additive can cure these kinds of problems — say unstick a ring — then your engine may well return to its former glory.

Can an additive give greater-than-rated power? Engine manufacturers say flat-out: No. Additives that claim to improve power do so by supposedly reducing internal friction. Considering that such friction consumes just four percent of the chemical energy in fuel (compared to the 45 percent sent out the exhaust pipe as waste heat), there's not much improvement to be gained. Even if you could eliminate half of the internal friction (which is unlikely), you aren't going to see any change on the airspeed or vertical-speed indicator.

So you should be skeptical when a product claims to boost horsepower, especially when it claims to do so while simultaneously reducing fuel consumption. One such product that claims to improve engine efficiency through reduced friction is Microlon. It is an FAA-approved additive containing Teflon; in its literature Microlon claims to have been responsible for a 37-percent power increase and a 12-percent fuel consumption decrease from a Detroit Diesel engine in dynamometer tests. That, of course, is apples to oranges compared to an aircraft engine in the real world.

I witnessed a test involving a Beech V35B owned by Japan Air Lines 747 captain John Deakin. In back-to-back tests conducted in April, the Bonanza performed virtually identically before and after the Microlon treatment. (This treatment entails adding Microlon to the oil supply and flying a short period — Deakin flew more than two hours — to let the product penetrate the engine's innards.) Sophisticated engine instruments (a JPI EDM-700) measured EGT and CHT for all cylinders; a time-to-climb test and two-way, GPS-verified true airspeed measurements revealed no detectable horsepower increase. For his part, Microlon chief Bill Williams claims that the treatment was not carried out properly, and that he has had significant response from Microlon users that the product works.

Further, in the intervening 50 hours since the Microlon treatment, Deakin has noticed no performance changes. A subsequent oil analysis indicated no significant change in wear metals; in fact, some metals levels increased. By all conventional measures the Microlon appears to have had no effect on Deakin's Bonanza, performance-wise.

Not all additives claim to boost power and extend your TBO. Beyond claims of performance improvements, additives can have some beneficial effects. Tricresyl phosphate, also known by the brand name TCP, is a popular extreme pressure (EP) additive. It is currently used in Shell's Aeroshell 15W-50 multigrade, semisynthetic oil and Lycoming's LW-16702 additive. This EP is intended as an anti-scuffing agent, to help provide lubrication in high-stress areas such as the cam/lifter intersection when either the regular oil exceeds its shear strength or when there is not sufficient oil flow for proper lubrication.

Lycoming is certain of the benefits of this EP. In addition, it is mandated by AD for use in the 76-series engines (which includes the O-320- H2AD and O-360-E) at each oil change to help ameliorate camshaft and follower wear. In these engines, long periods of inactivity and insufficient preheat in the winter can wreak havoc with the valve train. Oil flow to the high-mounted cam can take too long to arrive after engine start in cold weather, and subsequent scuffing of the cam and spalling of the lifter bodies has become synonymous with the engine type. Although there are still skeptics in the field who say additives like tricresyl phosphate have marginal effect on cam wear, Lycoming says otherwise, claiming long-term benefits. (Once again, we have an additive to cure a known engine malady; the best solution would be something like the Ney Nozzles (see " Airframe and Powerplant: In the Lube," March AOPA Pilot), which provide pressure lubrication to the cam and lifter faces.)

For decades pilots have sung the praises of Marvel Mystery Oil as a remedy for top-end distress and valve sticking. As the product is not FAA approved, pilots must surreptitiously add the stuff to the fuel and oil supplies, presumably while the FAA inspectors are out having lunch. There's much anecdotal evidence that MMO does help valve sticking. How? It's likely the result of the product's solvent-like nature and low viscosity index. It is a very light oil originally intended to prevent gum formation in carburetors; operators who use Marvel Mystery Oil today say it helps keep rings unstuck and helps valve sticking.

In practice, the solvent content gets into sludge-filled areas of the engine — ring lands, lifter bodies, valve guides, for example — and works deposits loose. Also, since MMO is such a light oil, it slightly reduces the viscosity of the total oil supply, making it possible that oil will reach lube-starved parts of the engine sooner after start-up.

While Marvel Mystery Oil has been with us since the early 1920s, aviation now has a new player, called Lenckite AvBlend. Actually, Lenckite has been around since the 1930s, but it was only recently approved by the FAA for use in certified aircraft. (Experimental drivers can use whatever oil treatment they like.) Now marketed under the name AvBlend, the product claims to provide medium-term lubrication to lube-critical components like valve guides and cam and lifter faces. (We say medium-term because AvBlend must go in at each oil change.) The product sells for $19.95 per 4-ounce can. One serving is supposed to be added at each oil change for engines with an 8-quart or smaller sump; a second can is recommended for larger engines.

According to Ed Rachanski and son Ed, Jr., owners of Blueprint Engines in Chicago and Techni Flyte, producers of AvBlend, the product has the ability to penetrate deep into the pores of the metal where it remains trapped. In time, the light, pure petroleum lube leeches out, lubricating the surface regardless of whether or not the normal engine oil film remains in place.

In addition, the company says AvBlend will soften and prevent further lead and carbon deposits; this is somewhat true of Marvel Mystery Oil, too. Where this pays the greatest dividends is in the potential to prevent valve sticking. Consider that the exhaust valve head and seat see temperatures of around 850 degrees Fahrenheit. Part of the heat generated in the combustion chamber is conducted through the seat to the cylinder and some of the heat travels up the valve stem to be deposited in the guide.

If the guide begins to lose the proper tolerances, oil will be sucked in and this flamethrower heat will quickly reduce the oil to a nasty carbon mess. Once the valve guide wears beyond tolerances, two things happen. One, the heat transfer path becomes smaller, resulting in a higher heat load for the parts of the valve and guide still in contact with each other. Two, the valve begins to move around on the seat, compromising its ability to seal and directing fiery hot combustion gasses at the stem and bottom side of the valve guide. Likewise, a valve making poor contact with the seat will have its heat-transfer path compromised, raising the temperature of the valve and accelerating guide and valve wear. It's easy to see, then, that deteriorating guides can quickly become a nasty, self-promoting problem.

How does AvBlend help? Mainly by preventing carbon buildup in the stem, keeping the guides clean and dimensionally correct. In addition, Techni Flyte claims that AvBlend will prevent carbon buildup in the combustion chambers, ring lands, and rocker-box areas. As a testament to its effectiveness, the company shows off a set of Lycoming HIO-360 cylinders run on an Enstrom helicopter; this ship was operated by WGN radio in Chicago as a traffic-watch helo. Upon first inspection, the cylinders and valves look quite clean, with normal wear patterns and no evidence of heat damage. The kicker is that they have some 7,700 hours in four overhaul cycles on them. (Indeed, it was a body of operator experience along with 1,000 hours of close scrutiny of this engine installation upon which the FAA based its approval. Note that FAA approval doesn't mean the product will do what it claims to do, or that the agency somehow recommends it. Rather, it simply means that the FAA has witnessed that the product will do no harm to an aircraft engine.)

More anecdotal evidence comes from American Flyers, a flight school with locations around the country and the operator of a fleet of mostly Lycoming-powered trainers. According to the school, once it started using AvBlend, valve sticking was reduced by some 75 to 80 percent. And this is from a concern whose fleet of 65 aircraft accumulates a total of about 6,600 hours a month.

To see just what AvBlend might do, we had a Mooney operator begin using the product a few months ago. With about 35 hours on AvBlend, he reported no noticeable changes and nothing abnormal in the oil analysis. He will, however, continue to use AvBlend, and report back to us should he notice any improvement or problems with his TSIO-360 Continental. Though a one-airplane, one-pilot sampling represents statistically shaky ground (which, quite honestly, applies to the Microlon test earlier), we hope to get some sense of the product's worth over time. To the Rachanskis' credit, they never claim improved power or TBO-busting longevity with the use of AvBlend. Instead, they call it a product that treats a specific set of problems common to many air-cooled aviation engines; it's a focused fix rather than an all-over, feel-good engine panacea.