By Sam Hoober, Alien Gear Holsters
And now for something completely different.
Something you might have heard from time to time is that motor oil can be used as a gun lubricant. Some say it’s better than most gun oils, some say it’s roughly equivalent, and some insist it’s all they use.
How true is it?
Let’s try to come up with an answer.
On its face, there’s no reason why it shouldn’t. Motor oil provides lubricity in engines until the molecular structure begins to break down due to repeated trauma from heat and all those moving parts.
It would also probably be best to use synthetic. Synthetic motor oil is now the preferred oil for new cars and has been preferred in luxury cars as well as high-end sports cars for quite some time.
Back in the 90s, Mobil bought a new BMW 325i off the lot, drove it around a bit to get it started, and then stuck it on a rolling road (a hamster wheel for cars) and left the throttle on at 85 miles per hour for the better part of four years.
They stuck to BMW’s service schedule, performing all maintenance at the recommended intervals. (Hint, hint.) Naturally, they used Mobil1 synthetic, but still. When the car hit 1,000,000 miles on the clock, they tore down the block and started measuring everything.
The clearances were still at factory spec.
So modern motor oil – and Mobil1 is not really exotic anymore – is no joke. Granted, I’ve had better results with Castrol GTX in my cars, but never mind; this is about gun stuff.
How, therefore, can a person tell how suitable motor oil might be for use as gun lubricant? By understanding the relative ability to withstand the stresses of the two fluids.
Now, what stresses are those going to be?
To a degree, there’s the sheer forces in the gun itself, but that doesn’t apply as much as you’d think. Force is actually acting on other things; in a semi-auto pistol, force acts on the slide, the barrel lugs, and to a lesser extent the frame rails, not the lubricant that coats them.
In a semi-auto shotgun or rifle, the force acts on the bolt and carrier and the recoil system more so than merely the oil that’s on it. So force itself is not a good measurement.
Neither is pressure. In engines, pressure is minimal compared to firearms. The most pressure that will be contained in any given engine rarely exceeds 1,000 psi; most engines have 200 psi or less when the piston is at top dead center.
Typical oil pressure is less than 60 psi for most cars.
Also, pressure in guns can be misleading. There is a lot of pressure at the chamber (20,000 psi to 60,000 psi+, depending) but remember that most of that pressure actually goes down the bore. That’s how guns make a bullet go fast!
Some cycles the action in a semi-auto, to be sure, but it’s drastically less than chamber pressure. So the ability of a lubricant to withstand pressure is likewise not relevant.
What’s left, then?
The most relevant measurement, really, is the ability to withstand heat. Since we can take it as granted that motor oil lubricates and withstands pressures and stresses just as gun lubricant, can motor oil put up with the heat?
Okay, so the measurements that used for lubricants are the flash point – the minimum temperature at which the substance can ignite at all – boiling point (obvious) and the ignition point, when it combusts.
Why is this relevant?
Part of the carbon buildup inside your gun is the ignition of the lubricant. It burns and vaporizes, leaving deposits inside the gun and reducing the amount of lubricant in the weapon. In other words, the more heat a lubricant can withstand, the longer it lasts when shooting.
Now, the hottest most guns get is somewhere between 250 degrees F to 400 degrees F, for the most part, if shooting semi-auto. Full-auto is another matter, of course!
So, how do some motor oils and gun oils compare?
The flash point for the liquid form of Ballistol, a very common gun lubricant, per their Safety Data Sheet, is 51.7 degrees C (125.06 degrees F) and the auto ignition point is 260 degrees C or 500 degrees F. However, the ignition point of aerosol Ballistol is 200 degrees C, or 392 degrees F.
Break-Free CLP, which is nominally the standard issue all-in-one lubricant/cleaner for the armed forces, has a flash point of 94 degrees C (201.2 degrees F) and an ignition point of 260 degrees C/500 degrees F, per Safariland’s SDS.
Lucas Extreme Duty Gun Oil has a flash point of 212.77 degrees C (415 degrees F) and a boiling/ignition point of 260 degrees C/500 degrees F. Pretty stern stuff!
Good old Hoppe’s Lubricant has a flash point of 192 degrees C/375 degrees F, and a boiling/cook off point of 315 degrees C/599 degrees F, per their SDS.
Another of Grandpa’s gun oils, Rem Oil, has a flash point AND auto ignition point of around 150 degrees C (302 degrees F) in liquid form and the aerosol form has a flash point of 136 degrees F and boiling/cookoff point of 262 degrees C/500 degrees F.
So, top tip: liquid gun oils are better than aerosols.
That said, how do motor oils compare?
Castrol Edge 5W-30 has a flash point of 220 degrees C/428 degrees F.
Just to be aware, flash points tend to get a bit higher with lower-weight motor oils, for the sake of consistency, we’re going to stick to 5W-30 for the rest of this article.
Mobil1 Synthetic, since they were mentioned, has a flash point of 230 degrees C or 446 degrees Fahrenheit.
So what’s the takeaway?
The takeaway here is that there’s DEFINITELY something to it! As you can see from the flash points/ignition points of these different lubricants, motor oil is if anything a little heavier-duty than most gun oils, though not necessarily all of them.
In other words, motor oil is actually more heat resistant than typical gun lubricant.
Ah, but what about cold?
The measurement for that is the “pour point,” the lowest temperature at which the fluid flows easily.
Motor oil would appear to have the edge here too.
Gun oil manufacturers don’t always disclose it. Of the above, Lucas Gun Oil Extreme Duty has a pour point of – 39 degrees F and Rem Oil (liquid) has a pour point of – 30 degrees C/-22 degrees F. They were the only manufacturers who mentioned it.
As to motor oil, Mobil1 has a pour point of – 45 degrees C (-49 degrees F), Castrol Edge at -39 degrees C (-38 degrees F) and Lucas Oil Petroleum is rated for – 36 degrees C/-33 degrees F.
So the lesson there is that motor oil is actually more resistant to cold as well for the most part.
In short, a lot of motor oil is a better oil than most gun oil, until it’s not, and there are some really good gun oils out there. Apparently Lucas Oil really knows what they’re doing.
But here’s where things start to get more interesting.
The typical bottle of Hoppe’s costs about $3 for a 2.25-oz bottle. A 6-oz bottle of Ballistol is about $9 to $10.
An entire quart of synthetic motor oil? About $8 in most stores. So that’s something to think about.
However, it’s also worth noting that motor oil is NOT a very good surface protectant, so that has to be taken into account. And traditional gun oils such as Rem Oil, Ballistol and now CLP do work fairly well for that, so it’s still worth it to have them around.
So, if you were curious about whether your gun will run well if you had to use motor oil? It will! If it’s good enough for Mercedes, it’s probably good enough for a Glock.
Sam Hoober is a Contributing Editor to AlienGearHolsters.com, a subsidiary of Hayden, ID, based Tedder Industries, where he writes about gun accessories, gun safety, open and concealed carry tips. Click here to visit aliengearholsters.com.