Default Boxster Engine Oil Filter Replacement Question
 

Can I replace the oil filter without having first drained the oil from the main reservoir? I ask because I had to change my oil last night (put clean oil in) without having replaced my oil filter. It was late at night and I couldn't get the oil filter off and had no way of getting to a store to get a new oil filter wrench so I just filled my oil and said screw it and left the old oil filter on. I just not a new wrench and want to change the oil filter now but obviously don't think that's possible without rechanging the oil again.********

I am pretty sure you can. It is even sometimes advised to change the oil filter only... so it will not drain the oil.

Yes, you can remove and replace the oil filter without draining the oil. Only a few drips should come out besides what is in the oil filter housing.

If you still have the plastic cup + cylindrical paper filter, I would suggest that, at your next filter change, replace the plastic cup with a spin-on filter adapter. Even when not excessively tightened, it tends to stick to the block so tightly that most cap-type oil filter wrenches will ‘cam over’ before the cup will let go. IMHO that plastic cup thing is the worst thing Porsche ever put out, rivaling the immobilizer- box-below-the-seat fiasco.
I found that the best-fitting oil filter wrench is the one marketed by Craftsman, of all things, better than the several European tools I have. Alas, the cups tend to stick so tightly to the block that it takes, I estimate, 200 ft-lbs, yes, 200, to get them off. Afterward, the cap wrench is stuck so tightly to the cup that it cannot be removed from it. I’ve got three of them to show for it. Of course, your mileage may vary.

+1 on the spin-on filter adapter.

Doc, you should just leave the tool on there when you put it back, then it’s already there when you need it 😄

Yes, you can remove just the filter. But unlike the other suggestions, I prefer to keep the original cup and cartridge. My main reason is that it's easy to inspect the cartridge for debris at each oil change. Not that their reasons aren't valid, it's just my preference.

If you accidentally overfill, you can remove the filter canister and dump the oil in it. Generally takes you down 1/2 a bar on the electronic scale.

986tate has the good suggestion just to leave a stuck cap wrench on the oil filter cup, in anticipation of the next oil change.
At the time, I needed the cap wrench to service my three other Boxsters, but that cap wrench is carried by Lowe’s under the Craftsman label, about $20 each, so you could just consider it a permanent modification to a particular car’s oil filter cup.
The cup has a flange which must be in firm contact with the engine block or it will leak copiously. It requires a lot of torque to reach the point of contact, and once installed under kinetic friction, to reverse the rotation beginning with static friction. Recall from your physics class that static friction is always greater than kinetic friction.
My larger concern was that the cup was stuck on the engine, and required such a high effort to remove it, exerted against the car while you are underneath it : a great way to knock a car off jack stands.
Yes, the paper cartridge filters are easier to inspect for metal than are metal-can ones. Summit Racing has an oil filter cutter for about $40, a tool you’ll always need and never wear out.
So, why did Porsche engineer the engine block and oil filter cup to have so much interference ??
Mercedes engines of the same era used a similar system : the filter used is nearly indistinguishable from Porsche’s, but their plastic filter appliance never gets stuck…