The following guide is the result of research used to answer an important question; what is the correct engine oil capacity for an early 928?
Seemingly simple question, however the answer was surprisingly more complex. See, from 1978 to 1983, Porsche specified 3 different oil capacities and offered 3 unique dipsticks!
The purpose of this guide is to condense specifications gathered from various Porsche publications, suggest a singular practical engine oil capacity, and identify dipsticks.
The scope of this guide is Porsche 928 from 1978 thru 1984. Engine oil capacity remained unchanged thru later years.
Before we begin, here are few important qualifiers:
- capacity specifications which included the modifier 'with change of filter' were used for this guide. If not clearly specified it was assumed logical and practical.
- practical oil capacity assumes a new oil filter was used when performing an oil change, and oil was drained after full operating temperature was achieved.
- oil pan, dipstick guide tube, and associated engine internals were not changed w.r.t. capacities for the purpose of this guide.
- volume conversions from litre (L) to quart (Qt, US liquid) are rounded to the nearest half or whole quart.
For 1978, Porsche specified 7.5Qt (7L). Then in 1979, capacity increased to 8.5Qt (8L), per Technical Information No. 4, 4.1.1979.
The effect of the change was 'better oil supply to the tappets when the oil level is at "min" and the car is not standing on level ground'.
As such, dipstick p/n 928-107-737-05 was obsoleted and superseded by p/n 928-107-737-06. At that time, the handle color changed from yellow to green.
The final change occurred in 1983, when capacity decreased to 8Qt (7.5L). Porsche did not issue an official change publication, however general publications ie. owner's & workshop manuals were updated.
Near this time, possibly earlier, dipstick p/n 928-107-737-06 was obsoleted and superseded by p/n 928-107-737-07. The handle color remained green.
Accepted principle is to regard Porsche's last specification as the most current, and all prior specifications are superseded. We can apply this to engine oil capacities and dipstick part numbers. Also, we can assume Technical Information No. 4, 4.1.1979 publication is obsolete.
Reviewing the image above, the 8Qt (7.5L) spec lands in the mid-range of the latest dipstick min & max marks. This is ideal gauging and a fair approximation. Also, the latest dipstick allows for prior capacity specs to fall in-range.
However, the latest dipstick, Porsche p/n 928-107-737-07, is recently no longer available (NLA) from Porsche. Earlier dipsticks are also NLA. You may find these available at 928 Classics Parts Store.
Identifying a dipstick may be challenging because the handle paint is most likely missing, plus there are 2 green variants. Do not assume your 928 has the correct dipstick for it's given year!
Reviewing the image above, you can see the yellow 78 dipstick is the longest - 316mm (12.4") vs. 299mm (11.8")
The 2 green dipsticks are the same length, but are notably different between min & max marks - 22mm (.86") vs. 24mm (.94"). Also, the location of the min & max marks are visually unique.
If your 928 has a dipstick modified per Tech Info No 4, 1979, it had been cut to 290mm (11.4") long. You may want to consider replacing it with dipstick p/n 928-107-737-07.
