Just in time for the start of the season, Porsche Classic is launching its own engine oil for air-cooled flat-four and flat-six engines: the Porsche Classic Motoroil. And if it says Porsche on the label, then you can be sure that there is Porsche inside. In collaboration with the Porsche Development Centre in Weissach, the new engine oil has been developed by the Porsche Classic experts with the specific aim of meeting the demands of the 356 and 911 models, including the 993 model range. Its operating behaviour and lubricating properties were put to the test in extensive laboratory-based tests and practical trials. The Porsche Classic Motoroil comes in two different versions: 20W-50 for all 356, 914 and 911 models up to the 2.7-litre G-Model and 10W-60 for flat-six engines from a displacement of 3.0 litres up to the 911 (type 993).
The engine is the heart of each and every Porsche, and air-cooled flat engines place particular demands on a lubricant. The thermal load is higher than in water-cooled units, for example, which means that the engine oil has to work harder to cool the engine down. The larger oil volume firstly entails a longer oil heating time, and secondly calls for optimum cold running behaviour. The traditionally high power output per litre of the engines also results in high compression and high pressures. Together with the different temperature zones which are characteristic of air-cooled engines, this means that the oil needs a high "hidden" performance reserve.
A compact and lightweight engine design means that the connecting rods will be short in relation to the piston stroke, which in turn means high lateral piston forces and correspondingly high demands on the lubricating film stability of the oil. In short, the older flat engines in particular can't just use any old oil. The development of an engine oil for classic air-cooled flat engines has therefore been something akin to a balancing act between tradition and innovation: as advanced as possible and as traditional as necessary.
Although modern oils are better from a technical point of view, this is not the case when it comes to classic air-cooled flat engines. For example, the low viscosity of a 0W-30 oil means optimum cold-start behaviour, low engine resistance and other benefits in modern engines. In a 356, however, an oil of this kind can result in leaks and increased oil consumption due to the engine's higher production tolerances and lower oil pressure during operation.
Modern oils also use highly efficient detergent/dispersant agents to thoroughly clean the engine and reliably remove dirt, which can be too much of a good thing for a classic Porsche engine. It is true that additional deposits should be prevented and oil-soluble contaminants such as soot, water and dust kept suspended until they are drained off through the oil filter or removed during the next oil change, but at the same time it is important that the deposits which have built up over decades are not suddenly dissolved and that seals are not corroded.
Since not every classic Porsche is in everyday use, the engine oil also had to meet other demands: classic vehicles are often left stationary for long periods of time and only moved intermittently and for short journeys, which means that condensation can form in the oil if the engine does not heat up fully. Aggressive combustion residues can cause acidification of the oil fill, resulting in the corrosion of engine components. The alloys, metals and sealing materials which were used at the time are at particular risk. Porsche therefore paid particular attention to this aspect when developing its Porsche Classic Motoroil. The special formulation incorporates a high alkaline reserve, which neutralises any acids that may form. Additional corrosion inhibitors also protect vulnerable components, even during longer stationary periods.