It started out as running to cold, maybe 60 according to the gauge, so I replaced the t-stat with one rated at 176 (80centigrade) now the heater works much better and the car seems to have more power,but now the gauge is reading around 90. Is 90(centigrade) to hot?I know that modern gas powered cars usually run around 195 or more, but I just dont know what a 30 yr old diesel should be running at. are these cars prone to bad gauges or sending units(79 300cd)? I also noticed that my oil pressure has dropped at idle from 3 bars to 2.25, should I worry about this? any advice is much apprecieated!