If you've been hunting for an aeroshell 64 equivalent because your usual supplier is out of stock or you're just looking for a more accessible alternative, you're definitely not alone. It's one of those staple products in the aviation and heavy machinery world that seems indispensable until you suddenly can't get your hands on it. Aeroshell 64 (which many of us still accidentally call 33MS, its old name) is a synthetic grease that's heavily relied upon for high-load applications, specifically because it contains molybdenum disulfide.
When you start looking for an equivalent, you aren't just looking for "any old grease." You're looking for a specific set of properties that can handle extreme pressure without breaking down or causing component wear. Let's dive into what makes this stuff tick and which products actually stand up as true alternatives.
The MIL-SPEC Standard is Your Best Friend
Before you grab a random tub of grease off the shelf, the most important thing to look at is the military specification. Aeroshell 64 is qualified to MIL-G-21164D. If you find another grease that meets this exact spec, you're essentially looking at a direct equivalent. This isn't just bureaucratic red tape; that spec ensures the grease has the right amount of "moly" (molybdenum disulfide) to handle those high-friction, sliding-metal surfaces that would chew up a standard grease.
You'll often hear people talk about MIL-PRF-23827 or MIL-PRF-81322, but those are different animals. If your manual specifically calls for Aeroshell 64 or the 21164D spec, you have to be picky. Using a grease without the moly additive in a spot that requires it can lead to fretting or even seized parts over time. It's a small detail that makes a massive difference in how your hardware holds up under stress.
Royco 64: The Most Direct Alternative
If you want the closest possible match, Royco 64 is the heavy hitter. It is specifically designed to meet that same MIL-G-21164D specification. For all intents and purposes, it is the primary Aeroshell 64 equivalent used in the industry today.
Royco 64 uses a synthetic hydrocarbon oil base and a lithium thickener, just like its Shell counterpart. It also packs that crucial 5% molybdenum disulfide. This additive is what gives the grease its dark, almost black color and its ability to lubricate even when the oil film gets squeezed out under heavy loads.
In my experience, Royco and Aeroshell are pretty much interchangeable in most logbooks. They feel the same, they smell about the same (which is to say, not great), and they perform identically in extreme temperatures. If your local FBO or industrial supplier has Royco 64 but not Aeroshell, you can usually swap them without any sleepless nights, provided your maintenance manual allows for the equivalent spec.
NYCO Grease GN 17
For those of you operating more on the international side or who have access to European supply chains, NYCO Grease GN 17 is another solid contender. It's a synthetic grease specifically formulated for those high-load airframe applications. Like the others, it meets the MIL-G-21164D requirements.
NYCO has a huge presence in the global aviation market, and their GN 17 is often the go-to substitute when American brands are hard to find. It handles the same temperature ranges—roughly -100°F to +250°F—making it just as versatile for components that go from a freezing-cold hangar to the heat generated by a working actuator. It's a reliable, high-quality option that won't let you down if you're switching over.
Why Mobilgrease 28 Isn't a Direct Match
A common mistake I see people make is assuming that Mobilgrease 28 can serve as an Aeroshell 64 equivalent. I get why—Mobil 28 is everywhere. It's the "red grease" that seems to be in every toolbox in the country. It's a fantastic wide-temperature grease (meeting MIL-PRF-81322), but it's not a direct replacement for Aeroshell 64.
The big difference is the molybdenum disulfide. Mobil 28 doesn't have it. Aeroshell 64 was actually developed to be Aeroshell 33 plus moly. If you use Mobil 28 in a place that specifically needs the anti-seize and extreme-pressure properties of a moly grease (like splines or heavily loaded sliding pins), you might run into trouble. Mobil 28 is great for wheel bearings and general airframe lubrication, but it doesn't have the "bite" needed for the specific tasks Aeroshell 64 is built for.
The Danger of Mixing Greases
One thing you really need to be careful about when switching to an equivalent is compatibility. Even if two greases meet the same MIL-SPEC, their thickeners might not play nice together. Aeroshell 64 uses a lithium complex thickener. If you're switching to an equivalent like Royco 64, you're usually fine because they share the same base chemistry.
However, if you happen to find an older or niche grease that uses a clay-based (Bentone) thickener or a different chemical structure, mixing them can be a disaster. When incompatible greases mix, they often undergo a chemical reaction that makes the mixture thin out and run like water, or worse, harden into a waxy mess that won't lubricate anything.
The best practice? If you're switching brands, try to clean out as much of the old grease as possible. If it's a closed component, purge it thoroughly with the new grease until you see the new stuff coming out clean. It's an extra ten minutes of work that saves you from a very expensive headache later.
Where This Grease Actually Matters
You might wonder why we obsess over finding the exact Aeroshell 64 equivalent. It's because of where this stuff is used. We're talking about highly loaded sliding surfaces—think landing gear bushings, flap tracks, and screw jacks. These are parts that don't just spin; they grind against each other under thousands of pounds of pressure.
The "moly" in these greases acts like tiny ball bearings at a microscopic level. Even if the liquid oil part of the grease gets pushed aside by the pressure, those solid moly particles stay trapped between the metal surfaces, preventing metal-on-metal contact. That's why you can't just "wing it" with a standard multipurpose grease.
Pricing and Availability Considerations
Let's be real for a second: sometimes the search for an equivalent is purely about the wallet. Aeroshell prices can fluctuate wildly depending on supply chain hiccups. Royco and NYCO often provide a bit of a price break, especially if you're buying in bulk (like 5-gallon pails vs. individual tubes).
It's always worth checking with multiple distributors. Sometimes a "boutique" aviation oil supplier will have Aeroshell 64 at a premium, while a general industrial lubricant supplier might have Royco 64 for significantly less because they move more volume. Just make sure the "Batch Date" or "Cure Date" is recent. Grease does have a shelf life, usually around three years for these synthetic types, and you don't want to buy an equivalent only to find out it's been sitting in a hot warehouse since 2018.
Wrapping Things Up
At the end of the day, finding an aeroshell 64 equivalent doesn't have to be a daunting task as long as you stick to the MIL-G-21164D specification. Royco 64 is your most likely candidate and is virtually identical in performance. NYCO Grease GN 17 is another top-tier choice if you have access to it.
Just remember to steer clear of general-purpose greases like Mobil 28 for these specific high-load tasks, and always do your due diligence when cleaning out old grease to avoid compatibility issues. Whether you're working on a Cessna or heavy industrial machinery, using the right "moly" grease is the difference between a smooth-running machine and a very expensive repair bill. Stick to the specs, and you'll be just fine.