I second bstreep and Aaron -- use only German filters and known high quality oil.

Cheap oil is cheap because it isn't the quality of good oil, there is no free lunch!

Synthetics are better lubricants, but they cost more and may not be suitable for old engines.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!