I've found a couple of liters of synthetic (10w45) and mineral  (10w40) motor oil. I always read about people buying mobil 1 instead of gun oil and was thinking about using these left overs at least for cleaning my ARs. And maybe keep using ballistol just for lubricate.
Would that be safe?

Motor oil has detergents so it would clean well, I would wear gloves though.

Motor oil is a lubricant, not a cleaning agent.

I lube all my firearms with Mobile 1 synthetic (1 qt = lifetime supply), but I don't clean them with it.

Yep.

Yep Yep

Clean with non-chlorinated brake cleaner
lube with Mobil-1
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profit.

Yup. I always save the couple ounces I have left over of new oil after my oil changes. Lasts me a while.

MPRO-7 does a better job and is completely safe.  Brake cleaner won't remove heavy carbon buildups, leading, or copper.  It does de-grease very well. Brake cleaner tends to have a lot of splash back and is not good for the skin, lips, or eyes.  It does quite a bit of damage to a protective face shield, so it really isn't the safest thing to be using on your firearm, or inside an enclosure.

You already have Ballistol.  Why try to reinvent the wheel?  Motor oil won't clean for shit.

ballistol for clean.

Motor oil for lube.

This isnt 2 years into a shtf scenario where all u have is motor oil.  Use cleaning agents to clean use the oil to lube if u want.

This

 

The ballistol will clean it just fine.

Honestly though if you lube all the correct friction points of the bolt you probably don't have to clean that often and can just scrub everything off the bolt with minimal effort. Just be sure to look at a FAQ or read up on the friction points of a ar15 and just make sure you cover that part with a dash of oil.

I recommend mobil1 grease rather than the oil. Mainly because if you put a small dash of it on the bolt friction points, you'll find you can just as easily wipe everything off. You can buy a tub at a auto store for about 7 bucks and it'll last you forever.

As always remember that CLP like Ballistol do more than just "clean" and "lube" your gun. Most of the time it is protecting your gun from rust and other elements out there. So while a lot of folks use motor oil, and perhaps there is nothing wrong with it, just note you're not getting the total protection you would with regular old gun oil. The cheapest gun oil will do a better job at protecting your fire arm than the most expensive motor oil ever would.

I just use it as lube

Cleaning a firearm with motor oil.  All I have to say is this, "If you can succeed I want to know your method."  Motor oil is a lubricant, though it has detergents in it, motor oil makes for a bad cleaner.
Many people use motor oil as a firearm lubricant with great success but as a cleaner, I have not herd of any success stories.

I agree motor oil alone is not a good cleaner but if you add something like Kroil to it, them you have your own CLP.  I use 1 part Kroil and 3 parts Mobile 1 synthetic it works for me.

Yes, it would be safe.

I use 10W-30 Super Tech full synthetic motor oil from Wal-Mart to lube my AR's.  Meets the same specs as Mobil  for you Mobile 1 snobs. .

I also use a home made gun cleaner called "Ed's Red".  Its egual parts kerosene, ATF fluid, mineral spirits, acetone.  I also mix it without the acetone for cleaning around plastic parts.  It does stink though, best to use it outside or in the garage.  A Google search will give you the history of "Ed's Red" if your interested.

I'm not 100% sure, but I believe mineral oil is used in gear boxes, and rear ends, not as a motor oil.