I have a 96 S-320 thats been on Mobile 1, 10w30 since new. At about 70K, I noticed the same problem, had it checked and was told it meets the min. for pressure. I tried 15W50 with little change, so now I take it out out gear at stop lights and at idle it reads about 2 to 2.5. I'am now at 103,000 miles with no problems i know of(nock-nock). Hope this helps.

Ron