I am having a problem with oil pressure. It's summer and I was running 10w30 and the pressure was runnning a little low but still in the normal range. When it was colder it ran at the half way point. When it warmed up it started dropping to the quarter point which is still in the normal range. I was told to change my oil to synthetic blend and up it to 20W50 for summer and could go back to 10w30 in the winter. It seemed to work for the first week but now it starts to drop down again just above the quarter point but goes back up to half when I have the RPM's over 2,000. Any ideas? I bought this long block new 2 years ago and has about 35,000 miles on it. It's a daily driver I use for work and plan on doing more work to it but I would like to make sure this isn't a major problem first.