Can someone tell me why my 1995 E320 oil pressure guage only work for 1st 10 mins after that it goes completely to zero. or it will work when engine is cool once temp goes up slight it is back to 0 bar only. Do I have problem with my oil switch guage? Car is running perfectly normal. oil level is right on. I also get occasional engine light comes on. How serious is this? should I continue to drive car or have it check? if is just oil switch can this be something I can do myself? Help please