Got a 2009 Dodge Ram, 5.7 Hemi with 15,000 miles. Have been running Q.S. Advanced Durability dino oil, 15w-20. Changed to Pennzoil Platinum, 15w-20 and now the oil pressure dropped from 58 to 53 lbs immediately after start up. When it warms up, it only dropped from 49 to 48 lbs. Filter is the...