The 928 despite it’s shallow sump still hold 8-quarts of lubricating gold. The oil is the lifeblood of the engine, so be sure you take good care of your engine and be sure to feed it the proper viscosity of oil. I’m a firm believer in full-synthetic oils. I’ve seen engines that have been run on synthetic and those that have been run on conventional oil, and they look very different. I think “blends” are a sham because you don’t know how much of each type are in the mix. It could be 1% synthetic or 80%. Just stay away from it.
The other consideration is the level of ZDDP in the oil. Because of the flat tappets in the 928 motor, a high ZDDP level is recommended. Anything above 1200 is sufficient.
Finally, be sure you run the right viscosity. I’ve tried several kinds, and I now exclusively use Mobil 1 15w-50. You can get it in the 5-quart jugs at Wal-Mart and it has the right ZDDP and the viscosity always holds up.
Changing the oil is very straightforward. The drain plug is on the diver-side of the oil pan. Simply place a drain pan under it (remember it holds 8-quarts) and pull the plug. Right above it is the oil filter. It simply spins off and the new one goes right back on. Be sure to lube the seal with some oil and only hand-tighten it. Replace the drain plug and add in your oil. Be sure to check the level on the dipstick and you’re done. Porsche recommended changing oil at 15,000 mile intervals for your 928. But if you don’t drive that many miles in a season, you should change it at least once a year.
Coolant is another critical fluid in your engine. If left too long it can become acrid and etch the heads to the point that you can have a head-gasket failure. The coolant does not seem to affect the block as much as the heads. Some people say you can use the “universal” coolant, but having seen what can happen when the coolant is left too long, I decided to follow the Porsche recommended formula of a Phosphate-free HOAT (Hybrid Organic Acid Technology) coolant and replace it once every 2 years. I have found that Zerex G-05 fits this, but I usually let it go to 4-years.
To replace your coolant, drain the radiator by removing the (blue) plug on the bottom passenger-side of the radiator. Then remove both drain plugs on the engine block. These are located about 4 inches in front of the bell-housing just below the exhaust ports for Cylinders 4 and 8. Be sure to run some water through the system once drained to make sure you have all traces of the old fluid out. Replace the drain plugs and add 2-gallons of Zerex G-05 and then almost 2 gallons of distilled water. You might only get the first gallon of water in at first. Start the engine and let the coolant system self-bleed the air out. Then keep adding.
BRAKES (and clutch):
The brake system is also a very important system that requires regular maintenance. Porsche recommends using a high-quality DOT4 brake fluid. The reservoir is located just in front of the firewall on the driver-side. You should always keep and eye on the fluid. As brake pads wear, the brake pistons will fill with brake fluid and push out to fill the gap. So as the pads wear, your fluid goes down. Most mechanics will recommend (as does Porsche) you replace your brake fluid every 2-years. This is because brake fluid is hydroscopic - that means it attracts water. The more water content, the lower the boiling point. If your brake fluid boils then you cannot stop.
There are many ways to replace your brake fluid. It is generally recommended that you bleed the furthest caliper away from the reservoir first and work your way up to the closest one. However the 928 is opposite. You want to start from the driver-front tire, then passenger-front, driver-rear, then finally, passenger rear.
If you happen to own a five-speed, the brake fluid reservoir also supplies the fluid for the hydraulic actuated clutch. Make sure there’s plenty of fluid in the reservoir, then have a helper pump the clutch pedal while you release them lead screw on the slave cylinder which is attached to the lower bell housing cover next to the starter. Do this two or three times and you should be good.
The power steering system does not use power steering fluid. Instead, it uses automatic transmission fluid. ATF Dexron. You can find this at any auto parts store. It is the same fluid as used in the 928 transmission.
Draining the Power steering system is not usually required. The reservoir is located on the driver-side fender just in front of the engine. So just make sure the fluid is topped up.
About the author: Andrew Olson
I'm a long-time 928 enthusiast. I like long walks on the beach and a soft shoulder to cry on... where's Brian?