#2 - The only pressures that matter are working pressures. The pressure of the system at rest is only a factor of the ambient temperature once there is liquid in the system.
#3 - The gasket between the oil filter housing and the block has been redesigned. It currently it a mixture of metal and gasket material and weights about three times what the original gasket did. The new # is 616 184 07 80.
#4 - When refering to oil viscosity, numbers like 20w50 are refered to as multi-viscosity oils. This is actually misleading as the benefit to these oils are that they are viscosity stabilized. This means that they stay at the same viscosity over a wide range of temperatures, rather than thining out. The larger the number the thicker (higher viscosity) the oil.
The concept of the numbers goes like this. A 20w50 oil is really a 20W oil that has the hot characteristics of a 50W oil. In other words if you placed 20w50 in one pan and straight 50W in another and heated them equally at engine temps they would be the same viscosity, but at cool temps they would be very different with the 20w50 being more fluid.
Currently the thought is that some major percentage of all wear (75% or greater) comes during the first few seconds of running before oil is uniformly lubricating. The manufacturers say that the use of thin oils is the best defense for this problem; thus all multi-grade oils are better by this thinking.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician