Changing the oil on the Boxster is somewhat easier than on other Porsches. There is no separate oil tank to drain, and there is only one filter, which is easy to access. Also, the filter is located so it doesn't spill oil on other parts of the car when it is removed. The recommended oil change interval is 15,000 miles, but I prefer to change the oil and filter at 5,000-mile intervals.
The first thing to do for this project is to get together the necessary parts and tools. You will need a genuine Porsche OEM filter, which comes with a rubber O-ring seal (Figure 1). You will also need an 8mm allen wrench, and the correct size oil filter wrench. I used a plastic wrench that fits several different sizes of filters, one of which happened to be correct for the Boxster (Figure 2). The oil filter for the Boxster unscrews just like the filters on the 911s, but the similarity ends there. The Boxster filter is a plastic housing with a replaceable paper cartridge. This plastic housing is meant to be reused indefinitely, so don't use pliers or any other tools for removal that might pierce or crack the housing.
To begin, jack up the car, and use safety stands. Make sure it is secure, because you will be working underneath. For the correct way to jack up your Boxster, see http://www.pelicanparts.com/techarticles/box_jacking/box_jacking.htm . For this procedure, it is necessary to jack up only the left side of the car.
Put a large drain pan under the car to catch the oil. My favorite one holds 16 quarts, and it doubles as a storage tank to hold the used oil until you take it for disposal (Figure 3). I also use a drip tray under the drain pan to catch any oil spills. Remove the oil drain plug, keeping mind that the oil comes out quite fast. Be especially careful if the oil is hot.
Remove the oil filter by turning it with the filter wrench (Figure 4). The filter housing will come off, leaving the paper cartridge hanging from the filter base on the engine. Remove and discard the filter cartridge. Replace the rubber O-ring on the filter housing, and oil it lightly (Figure 5). Working under the car, replace the filter cartridge by pushing it onto the extended portion in the center of the oil filter base. It fits correctly either way-there is no top or bottom. Screw the oil filter housing onto the engine by hand. You can feel when the rubber O-ring begins to seat, and when the filter housing bottoms onto the filter base. Tighten the filter housing to 25 Nm (18 Ft/Lbs).
Replace the crush washer on the drain plug. Reinstall the drain plug and tighten it to 48 Nm (35 Ft/Lbs).
Lower the car. Refill the engine with nine quarts of oil, making sure to put the oil in the correct filler-it has a yellow cap, marked oil (Figure 6). The Boxster has a small funnel built in to the oil filler, but I like to use a large one to reduce any chance of spills (Figure 7). For the climate where I live (Southern California), I use Mobil 1, 15w-50. Check the oil level with the dipstick, and then verify it by turning the ignition switch to the "run" position and reading the oil level gauge. Start the engine and check for oil leaks.
Take your Boxster for a spin and enjoy the fact that you just saved about $100!