If you're talking about the 2.8DT engines, in our case the '92 - 2001 models, the pressure readings looks(sounds) normal.

When the oil is still cold @revs above 2000 the reading will be around 4bar, as it heats up, at idle it will be 1bar and at normal working revelutions (2500 - 3250) it can be between 2-3bar

Use a good quality multi grade oil, shell super rumela X for example, and change it on regular intervals, and you should not have any problems.