Porsche recommends replacing the oil and filter every 7500 miles for turbocharged cars and every 15000 miles for normally aspirated cars. This is one of the few times I feel that Porsche erred in the non-conservative direction with regards to a maintenance interval.
Frequent oil changes are vital to the longevity of a car's engine. Consequently, I change the oil and filter in my own car's religiously every 3000 miles. I don't recommend allowing a car to go more than 5000 miles between oil changes. Regardless of how often you decide to change your oil, pick a replacement interval and stick to it. You'll see better long-term performance from you car's engine.
17 mm socket and ratchet OR 17 mm combination wrench
Approximately 5.5 liters (5.8 US quarts) filled to the upper dipstick mark
Oil Drain Plug Seal Ring (26 x 32 mm - 900 123 049 30)
* You may also use the Mahle OC 75 Oil Filter which is a taller version of the OC 142. This filter was used on some 911 Turbo models.
If you happen to lose or damage the Oil Pan Drain Plug the Porsche part number is N 016 164 1. It is an M20 x 1.5 plug and you may be able to find it at an Auto Pats Store without having to buy it from Porsche.
Run the vehicle for a few minutes to warm the engine oil before remove. With the oil warm it tends to flow better and thus remove more sludge / deposits from the engine.
Raise the front of the vehicle on jack stands or ramps.
All 944s came from the factory with two skid pans. One covered the front-bottom part of the engine compartment (below the accessory belts). The other covered the bottom-rear part of the engine compartment (below the oil pan). To do an oil change, the rear skid pan had to be removed to access the oil pan drain plug. On most 944s, this rear skid pan has long since been discarded. Most 944 owners found it much easier to change the oil if they didn't have to remove that pan every time. Also, the engine tends to run a bit cooler as there is more air flow across the oil pan and hence better oil cooling. Again, most 944s don't have this pan anymore but, you may find that your 944 has this pan in place. It will have to be removed to change the oil.
Some folks will tell you that the oil filter will not make as bit a mess if you punch a hole in the top of the filter before you remove it. Other folks will tell you it makes no difference. And, some folks will tell you it makes an even bigger mess. Anyway, if you decide to try this, punch a hole in the top-center portion of the filter before removing the oil pan drain plug. The oil flowing out of the pan will help draw the oil out of the filter and make this method more effective.
Place a catch pan underneath the oil pan below the oil pan drain plug.
Using a 17 mm socket and ratchet or 17 mm combination wrench, remove the oil pan drain plug.
After the oil has drained for a few minutes, remove the oil fill cap. If you didn't punch a hole in the oil filter to help it drain, you can remove the oil fill cap prior to removing the oil pan drain plug.
Inspect the oil pan drain plug seal ring. If it has scratches or gouges, or if it is deformed at all, replace it.
When the engine oil has completely drained, replace the drain plug with seal ring and torque to 50 Nm (37 ft-lbs.).
Move the the drain pan underneath the oil filter area.
Stuff as many catch rags as possible around an below the oil filter. Using an appropriate oil filter wrench, remove the oil filter.
Apply a coating of new engine oil to the seal ring on the new oil filter. This prevents tearing the seal during installation and also makes removal of the filter easier in the future when you have to replace it.
Install the new filter hand tight. Most manufacturers don't recommend using a filter wrench to torque a filter on during installation. You can but, don't turn the filter more than 1/4 turn past hand tight.
Fill the engine with new oil and check the dipstick level prior to starting the engine. Fill to at least the high mark as some of the oil will be pumped up into the oil filter and remain there when the engine is started.
Start the engine and check for normal oil pressure.
Remove the car from ramps or jack stands. If jack stands were used stop the engine before removing the car from the jack stands.
Stop the engine and allow it to sit for 5-10 minutes to allow all the oil to drain back to the pan.
With the car sitting on level ground, check the engine oil level again and top off as necessary.
Take the used oil to an approved disposal facility.