80-90w gear oil
I tried heavier oil for a while and it seemed to possibly have advantages just from being thicker. Two things I began to notice was it didn't spread over the chain as well/thourougly. And it ended up collecting in the pinion area and then slowly seeped out. This was just sort of annoying from a drippage standpoint. Generally if you over oil with 80-90w it'll collect and drip but if you wipe the area off it's basically done. With heavier oil, it seemed to come back and back and back.
In the video I made, I show (as also outlined by Kaw) apply the oil at the rear of the bike. When you apply it, rolling the wheel backwards gravity will pull the oil to the inner part of the chain. If you're new to oiling, one testing you can do is oil the chain then just check by putting your fingers on the inner part of the chain. This is one reason to wipe the excess off as much as you can, what gravity pulled in centrifigal force will pull out. If you put your finger in and it comes out all wet, you can even wip the inner part of the chain.
But no generally I oil ever 400 miles after washing the bike. After the first ride or two, I might wipe the fling off the rear wheel. But it's oil, so it's effortless. I have an old wash mitt designated for that duty (oil/grease/chassis stuff) and it wipes off and I'm done in a couple minutes.
If you switch to oil there will be a learning curve. Sometimes you might apply a little more oil to clean it off and it might require a little more wiping. If you just got done running high speed stuff you might re-oil for good measure.
But you can trust it's a good and proper lube. If you're getting less 20k miles or less out of chains and sprockets there's no way chain life will be any less, my guess is, honestly significantly longer. Next time I change tires I'll provide an update on my sprocket wear. With over 20,000 miles my stock sprocket still basically looks new comparing side by side to a brand new sprocket. Chain stretch has really been minimal too.
My opinion/experinece is people are going through a lot of time consuming routine using "consumer chain maintenance products". The keyword is consumer, because that's what they want... you to buy more lube, buy more chains, by more sprockets, hire this stuff done. Just like a good little consumer should.