Which motor oil for AR?

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I've read countless arguments for and against the use motor oil on firearms (especially ARs). Many long time users swear by it.

So, if one were going give it a try, what brand and weight synthetic would BITOG'ers recommend? Most of the gun forums just say M1 5w-30, but I'm guessing that's just because it's the most common.

Any reason to consider PP, PU, M1EP, or others? Certainly cost is not a factor when only a few drops are used at a time. Thanks for your thoughts.
 
Id guess at it depending on which part of the weapon you want to oil. T protect the outside while it's in storage a light spray of WD40 on a rag wiped over the surfaces will stop it rust

To lube sliding parts of the action, try and think of a similar environment in a car.
Do the parts you want to oil move quickly or slowly? D they slide across each other or does one 'punch' into the other..Ike how bearing grease needs to stay put where engine oil needs to be..unviscous? It's totally application specific

I'd be thinking moly grease, white lithium grease, redline 70w drag oil and possibly something like an ATF or PSF?
 
The marines in the early days of the M16, when cleaning and maintenance supplies were rare, used diesel oil. I knew a marine from those days that swore by Mobil 1 15w50
 
engine oil is generally excellent for allround lube duty and on gun parts, sewing machines, bikes etc it would work just fine. I even think that sometimes it is superior to some "gun oils" around, just overlooked because it is so cheap and easy to get.
So in the AR I would use any oil, preferrably synthetic. 75w90 gear, 5w40 engine oil is just great. As always, all sticky surfaces attract powder dust so oil it, shoot, clean it (spray, kerosene etc) and re apply oil where needed.
Some areas need a light grease, and again, vehicle grease is excellent.

I also like frog lube, but in the real cold, naah. Engine oil it is.
 
I appreciate all the replies. There seems to be little consensus on which weight to use. Maybe use heavier weights for longer term storage?

Thanks again.
 
I think the heavier oils are probably best for hot weather and thinner if you are shooting in the cold.

Also some guns just like thicker lubes/greases. I would think something like an M1 carbine, a Mini 14, or an M1A would want thicker oil. I know my M1 carbine tends to sling thin lubes as it cycles.
 
Originally Posted By: Olas
I'd be thinking moly grease, white lithium grease, redline 70w drag oil and possibly something like an ATF or PSF?



Have you ever shot/touched/owned/maintainced an AR15? Living in England, one would assume there is a 99.99999% chance the answer is no. Almost all of those recommendations above are "interesting".
 
I used Mobil 1 5W30 exclusively for about 1 year. It worked. I didn't care for the smell so went back to dedicated gun oils. Motor oils don't really offer any benefits over a good gun oil, other than price, in my observations.

Brand/weight wont matter much. 5W30 Mobil 1 will perform the same as 5W30 Pennzoil Platinum.

My recommendation is to just spend a few bucks more and go get a good dedicated gun oil that will work in your weather and shooting conditions.
 
1 Data Point:

Two months ago I was breaking in a new AR - a tested upper but with new BCG. It was about 20F and dry outside, and the bolt was coated with Break-Free. The bolt seized after about 12-15 rounds. Again, this was a new aftermarket bolt not previously used in the gun/upper.

After freeing the bolt, I cleaned it and coated it with PP 5w-30, went back out and ran 40 to 50 more rounds through it w/o a problem. Previously, I had not been entirely happy with using Break-Free and Mil-Pro 7 as lubes on my AR bolts; they worked but felt a little rough. I'm going to be switching them to the PP this year and seeing how they feel and operate. I notice no smell with it; I have heard others complain about the M1 smell but I've never used it as other than in an engine.

I chose the PP only because that was my last oil change on my SUV, and I had the idea with the left over bottles that I'd squeeze out the residual oil in them for a gun/handyman lube. I set them upside down in a funnel mouth and let them drain a long while each into a small empty bottle I had on hand. Out of 5 quart bottles, I probably gathered another 2.5/3 ozs or so that I didn't get out when filling the truck. I'm using that as a gun oil to see how things shake out.

I had a 1911 disassembled for some refinishing work, and I re-assembled it with the PP. I'll see how that fares this coming weekend I hope. I've had this particular 1911 about 20 years now, so I am familiar with how it cycles and I can notice a difference.
 
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The break free was likely too thin and did not have as good of a film strength as the Pennzoil Platinum. That may explain the feeling of roughness vs smoothness.
 
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I think motor oil is not a very good thing for weapons...the emulsifiers in motor oil allow the water to penetrate the oil surface instead of repell it.

Take the oil you are gonna use..mix it(shake) it with water and it should seperate.

This is 'my' opinion only..if I am wrong tell me why (I'm not being 'smart')

ATF works well and if you want to thicken it up a bit put a little gear oil and mix it.
 
I've read a few tests of corrosion resistance that involved placing pieces of steel that were treated with various gun oils and left out in the elements. I don't recall any of them using a motor oil in the comparison.
 
Originally Posted By: Al
I think motor oil is not a very good thing for weapons...the emulsifiers in motor oil allow the water to penetrate the oil surface instead of repell it.

Take the oil you are gonna use..mix it(shake) it with water and it should seperate.

This is 'my' opinion only..if I am wrong tell me why (I'm not being 'smart')

ATF works well and if you want to thicken it up a bit put a little gear oil and mix it.


ATF will mix with coolant just as motor oil will. I have seen more than one instance of this in my wrenching days when the trans cooler in the radiator sprung a leak allowing coolant intrusion.
 
Originally Posted By: Robenstein

ATF will mix with coolant just as motor oil will. I have seen more than one instance of this in my wrenching days when the trans cooler in the radiator sprung a leak allowing coolant intrusion.

It may mix with coolant..which I seriously doubt but id doesn't mix with water. Pour some ATF into water and then some motor oil in water and then shake them you'll see.
 
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Originally Posted By: Robenstein
Coolant is often cut with 50% water and many use the same basestocks as oil (group II, III, etc.)

Whats your point? My point is that ATF doesn't mix with water like motor oils do. Therefore therefore oil will penetrate the barrier that oil puts down on the firearm. I will admit that motor oil has corrosion inhibitors...so maybe that makes it suitable..I don't know.
 
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Since I use M1, 5W-40 TDT in many things around here, I have it in an oil can too.

In a pinch, I used it on my 1911 pistol and it worked really, really well. So, I started using it on my AR10 and AR15. Great results.

I can't claim it's better than other motor oils. But I will claim that it's 400% better than rem-oil and the other gun oils I've wasted money on.

It does not foul up with carbon, and the semi auto action is clearly more reliable. Plus, cleaning is a snap. Good stuff indeed.
 
Originally Posted By: jkasch
I've read countless arguments for and against the use motor oil on firearms (especially ARs). Many long time users swear by it.

So, if one were going give it a try, what brand and weight synthetic would BITOG'ers recommend? Most of the gun forums just say M1 5w-30, but I'm guessing that's just because it's the most common.

Any reason to consider PP, PU, M1EP, or others? Certainly cost is not a factor when only a few drops are used at a time. Thanks for your thoughts.



If cost is not a factor, then why are you not using a dedicated firearm lube? Sure - they are more costly per oz. But you just said cost does not matter.

Two topics here; you need to decide which is importnat and when ...
lubrication
rust prevention


I use general Rem Oil for operation; never had an issue in decades. I use WD40 as a rust prevention for long term storage.


Use what you want, but I don't really think it will matter which syn you select at all. They are good, but not optimized, for firearm use.
 
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