I have been having strange oil pressure readings for a while. When the vehicle is started and driven, the oil pressure goes down to zero when accelerating. This is the opposite of what I am accustomed to on most vehicles. I have changed the oil pressure sending unit but that did not fix the problem. A light displays on the instrument panel that says "check gauges". There is no engine knocking or valve tappet noise so I have been still driving the vehicle. I noticed that during the summer months I don't have the problem. What would summertime temperatures have to do with oil pressure readings.