My contribution to the discussion - having worked with many 1.9 PD engines.
The only current approved oils for PD engines are those to VAG spec. 505.01 and 507.00.
The use of other oils may endanger the valve actuating cam lobes and their followers. Generic specifications such as ACEA and SAE/API are of no use whatsoever in defining the correct oil for these engines.
However (and this is the substance of the poster's question) the stated viscosity of the 505.01 oil is SAE 5W-40 and that for 507.00 is 5W-30. Which gives the better results?
505.01 spec oil is semi-synthetic and 507.00 oil is fully synthetic. Oil temperature is generally not a problem with these engines unless worked impossibly hard. Their thermal efficiency is so high that keeping these engines warm enough under light load is more of a problem. VAG know this and wisely limit the total oil volume to 3.6 litres.
So, we now have a relatively small volume of oil carrying out a tough lubrication job on highly loaded cams and the turbocharger spindle bearing. For my money, I would choose the fully synthetic 507.00 any day, giving lower oil drag loss at the (lowish) oil temperatures, good stability and maintenance of viscosity index throughout life, and the much reduced likelihood of varnish formation on the turbocharger bearing shaft following soak back heat.
These engines do not have undue lubrication problems throughout their very long life when properly used with either oil but my findings suggest that the fully synthetic 507.00 provides an extra margin of safety for little extra cost. Remember also that after prolonged use, a semi-synth oil is likely to suffer VI degradation more than the fully synth, and the 505.01 oil may be nearer 5W-20 towards the end of its life.
I have found that the 150PS PD engine (ARL) is prone to camshaft wear irrespective of lubricant choice.
Use 507.00 oil and change every 7k miles.
659.
Edited by 659FBE on 21/09/2013 at 19:38
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