Hi, I got a cartridge filter on my 2007 rav4. I have never changed oil with these filters, and I just couldn't get the small flat metal cap off, I think the cap is used to drain out filter oil before filter, so I kinda left it there by just remove whole filter, after iam done there were 2 plastic rings and I replaced the bigger one, I think small one is for the cap, so it's ok to leave it like that every time in change oil?

 

Yes, it is ok to leave that cap in place. I don't ever take the drain cap loose unless it's leaking.

If you got a factory toyota filter, there is a small plastic drain that inserts into the whole that the cap plugs. When you insert that drain, it pushes a one way valve open and drains the cartridge. In my experience, it makes even more of a mess that way.

Here's the factory filter for your rav4 (assuming its a V6 as the 4 cylinders still used a standard filter in 2007.) with the small plastic insert I mentioned on top of the bag containing the o-rings.

 

This man is correct.

Honestly, if you don't use the drain, it's a lot messier than if you do, because oil will spill all over your hand when you remove the filter assembly. To be fair, the plastic drainer DOES kinda require a certain technique to use, and if you do it wrong, it can create a mess anyway. I know this because I do oil changes on Toyotas all day.