Blokey, the copper based lube that comes on a new Glock is only for break in and is a mild abrasive similar to anti sieze. It is not to be re-applied. When I attended the Glock armorer's school about 7 years ago the Glock factory recommended any "gun oil" applied in 6 droplets to the specified lube points. Glock did not recommend any lube but they gave the students a bottle of Breakfree CLP to use for the class.
I have had at least a dozen Glocks over the years and have found them to perform the best with very, very small amounts of oil. If you think a glock does not have enough oil wipe half of it away and it should be just about right.
As for gun lubes and motor oil many shooters have been using M1 for years and it works just fine and so does ATF, 30wt, 5w-20, 10w, wheel bearing grease, 3 in 1, wd40 etc etc....None of these are ideal but they all will make guns work. Most guys that use M1 on guns use the 15w-50 because they think thicker is better and on firearms this is far from ideal. Actually most modern guns (last 50 years) will work best on the thinnest oil.
The only problem I have found using engine oil on guns is that it attracts far more dirt,dust, and lint than gun oils and that is a major problem on carry guns.
Take everything you read on glocktalk with a grain of salt. I have been a member there since 1999 and it is the most "uneducated" gun board on the internet.
Ulver I keep running into you everywhere. crownvic.net....glocktalk....bitog...whats next?