Which type of oil would do a better job in preventing corrosive wear in a engine? A hdeo or a pcmo synthetic or a mineral pcmo. This is in relation to short trips in cold and warm weather. Interesting that my last oil report at only 2000 miles showed 31ppm of iron in the months of may and june. The engine is a 3.7 v-6 with 6000 miles. Lot's of short trips with lower speeds which increase engine temps. I would suspect. I looked down the oil fill neck and could see sings of rust and deposits. I was using Castrol syntec blend but changed to amsoil 10w-30 to see if the iron would come down. Yes the motor might be still wearing in but it seems that even in warmer months there is still enough condensation to cause major problems.