My 75' 280 is running better! But now the oil pressure falls to 0 after a few minutes. I have been told to try tranny fluid with my oil and run a few hundred miles and change back. Is this a good idea? I took it to a mechanic (non-Mercedes) and he told me I needed a new moter but he didn't mention anything about an oil pump, which is what I think the problem is. Any suggestions?