Is there a benefit to using fuel additives?

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.


  1. Mark says

    I’ve been suing a product called Oxytane, which seems to bring 94 octane to 100, Maybe not a true additive but a electrolyte inhancer to promote better spark transfer

  2. Nick Jones says

    I’m not a chemist and I don’t play one on TV, but we have 2400+ hours on our O320-D3G and we use CamGuard with Phillips X/C based on the findings from Aviation Consumer that had a very well researched article. Our Cherokee 140 spends months of inactivity during the winter (hard to imagine in a plane with 10 owners). We were experiencing severe wrist pin plug wear when I bought into the group. Our suspected we had cylinder corrosion as the culprit. We removed the aluminum wrist pin plugs with the newer design Aluminum/Bronze wrist pin plugs, still had wear. We changed to the CamGuard and Phillips X/C concoction and the wear tapered off to the point that we do not get any wrist pin plug material showing up in the filter at 50 hour oil changes. Like I said, I’m not a chemist but I have seen results.

  3. Jim McG says

    I’m wondering about Slick50. I’ve used it in cars for decades, even back when it was multi-level marketing before going into stores. Proof it works to reduce friction: I had a Honda 550 motorcycle and treated it. Big Mistake! 24 hrs later the engine was in gear and going like it would at 60 mph, and my feet were on the ground and the bike went nowhere. Then I learned the clutch is in the oil bath. The Slick50 frictionproofed the clutch. I had to drain, flush, and change plates, then all was OK. Slick50 had an STC and flew a plane with double oil pan (to prevent pollution) and would pull cable and drain oil while flying. At slightly reduced power the plane would fly at least an hour, then do it again. I’ve used in my cars, but don’t in the plane. Slick50 quit promoting for aircraft because of cost of STC for every engine model. I sure would like to know if there are any side-effects and if it is safe to use in my C172 O300 that’s at 1,000 hrs SMOH now. I have no interest in the product, but do know it reduces friction.

  4. Ray says

    Snake oil, HA HA. Yeah, I have a motorcycle shop and I have customers that insist on adding “octain boosters” and other questionable products that promise the moon. These products are like flashy fishing lures that catch more fishermen than fish.

  5. Kenneth Hetge says

    I have regularly used AvBlend in my IO-550-G2B powered Lancair Super ES and can actually see and watch my fuel flow at a given power setting go down when the AvBlend is added to my engine oil. This number with the AvBlend is 13.1 GPH at max power, leaned to peak (1452*), 2400 rpm at 10,500. Without the additive or after it has flashed out, I see my fuel flow increase to 13.3 GPH. My engine was new from Mobile when I got it and I started using Avblend righ after the break-in. It now has 800 hours on it without a top and all compressions in the mid 70’s. I have operated this engine at peak EGT from day 1. In my case, it has worked. I speculate the additive is reducing the internal friction on moving parts and allows more bang for my buck (the same performance using less fuel).

  6. Ibrahim says

    In general speaking way we need additives in fuel , if you go back to the basic all types of fuels coming from crude oil , in aviation different behaves affecting in low and high altitudes / low flash point and high flash pint . In simple way speaking additives required in high altitude to prevent fuel from getting frozen not to form a crystal ice and this might Causes blockage in fuel line , in low altitude to prevent fuel In order not to evaporate.

  7. Walt Ray says

    Overhauled a Cont. 0-300D with 3700 hrs since new and the owner states he used Phillips
    cross country and motor honey. The crank miked out standard and the cam lobes showed
    no pitting or signs of ware. Cam followers also showed the same. Cylinders were changed
    out but showed very little ware and no scuffing. I can’t argue with the results but Phillips
    is my oil of choice, and motor honey is not on the shelves that I can find.

  8. Greg Ellis says

    I am not sure how much CamGuard adds to performance like you mentioned in your article but what I believe it does is allows the oil to stay on critical parts longer when the engine is not in use. This protects against corrosion and also against dry parts rubbing against each other when you start the engine. Aviation Consumer, I believe, had a pretty good write up on additives.

    As far as spark plugs fouling, leaning aggressively on the ground to the point that if you tried to put in take off power, the engine would stumble may help to prevent your plug fouling. In my Mooney, it is recommended in the POH to lean aggressively on the ground. Also, I believe the Cherokee 180 is carbureted and you may have the option of a different carburetor that runs leaner on the ground to prevent fouling. Just a thought.

  9. Hugh says

    Ben, What about TCP? We have a 1967 Cherokee 180, with TCP added to 100LL we only occasionally have a fouled plug requiring cleaning before flight, without TCP the plugs continually build lead and foul.

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