changing the guage is only part of the issue. did you switch out the sending unit. That is what actually tells the gauge the pressure with an electric signal. Unless you have one of the older ones where the tube actually goes into the guage in wich case ignore my ramblings. I still maintain that a quart of oil every 3k is not normal. My 220d never used oil over a 5000 mile interval. Nor did my folk's 300td's.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)