Teenage son drives 93 Honda Accord with 145K miles. Mixed highway and city driving, 3-4K OCI's. I have used and been happy with Pennzoil HM 5W-30 (10W in summer). Motor does not leak or consume oil. Would there be a benefit, however small, of using 1 qt Pennzoil Platinum synthetic with 3 qts HM at next oil change? Best of both worlds (semi-synthetic with seal conditioning) or asking for trouble? Car has always used regular dino or HM except for one OCI with GC (discontinued due to increased engine noise). Thanks for your feedback.