I have recently received several inquiries concerning the use of aviation fuel and lubricant additives. To start a discussion on additives, I’ve looked into any and all approved additives.
In the ASTM D-910 spec for 100/130 low-lead avgas, there are only two fuel additives approved for aircraft owner addition to the fuel: Isopropyl Alcohol and Di-ethylene Glycol Monomethyl Ether. Both are fuel system icing inhibitors.
The military has approved the use of Tri-Cresyl-Phosphate for use in both the oil and fuel — this approval covers the Lycoming LW 16702 additive — and the use of a Mil-C-6529C additive as an anti-rust oil additive. This is the active ingredient in preservative oils like Aeroshell 2F and the Phillips equivalent.
Once you get past this short list, we get into a gray area. For example, Marvel Mystery Oil, and the chemically similar Avblend, may not really be approved but have been used for many years. The primary reason for using these additives is to reduce intake valve sticking.
I have been looking for any statistically significant data that will prove or disprove this use. I have never found any, but I have talked to a lot of pilots who swear that the use of these products has eliminated or at least reduced the incidents of intake valve sticking.
On the positive side, there are no real negative side effects to their use except for over treating, since you lose about one octane number of the fuel for each percent of additive treat.
There is a whole host of additives for automotive use that promise a wild list of performance advantages. Many of these contain Zinc Dithio Phosphate, which can attack soft metals like silver and/or copper alloys and can cause premature problems or failure. That’s why I always recommend against the use of any automotive additive in your aircraft.
The latest oil additive for the aviation market is CamGuard. I have received numerous questions about the product, with some people saying it worked, but I have not seen any real data on the performance of the product in the real world.
The first thing I noted is that in the ads for the product it shows an almost new piston with a label of “500 HRS W/CamGuard” and a second picture of an apparent scuffed piston labeled “Without CamGuard.” I would think that a product named CamGuard would feature pictures of camshafts.
My other concern is the “without CamGuard” piston does not say how many hours are on it. This piston could have over 2,500 hours on a mineral oil for all we know.
Since I could find no data on the use of the product, I contacted several knowledgeable aircraft engine rebuilders for their opinions. The question I asked them was whether they had seen any engines run on the product and whether they had observed any benefit from the product. Now this was not a scientific survey and had a relatively small sample, but the answer was that none of them had seen any improvement that could be attributed to the additive. So the bottom line is that the additive does not seem to hurt performance, but may not provide any significant benefit either.
My problem here is what I call the economics and psychology of oil additive usage. We know that the secret to going to full TBO in an aircraft engine is proper maintenance and regular usage. When a pilot pays $25 or more for an additive, they automatically think they have protected their engine against all harm. In turn, they may extend their oil change interval, not worry about their oil temperature, or just reduce their maintenance practices because they believe the oil additive will protect them.
I do not have any problem with this FAA-accepted product as long as the aircraft owner still follows the recommended oil change and other practices recommended for their aircraft.