Originally Posted by mobilaltima
Friend of mines car, 60k miles with the 3.5 V6. I have 4 quarts Pennzoil Platinum 5W30 thats pretty old, SM spec, that I dont have use for. Would it be ok to mix these 4 quarts with a quart of SN Pennzoil Platinum? I told her just to buy a quart and a filter and I'd change it for her. Jug of SM platinum looks to be from 2009 or 2010, pretty old.
Shake it good when pouring and I prefer to buy a five quart jug for needing that extra quart. It's a-lot cheaper per quart. You will eventually use the other four quarts in that jug. Plus, odds are, it may need a quart between your OCI.
It's been a couple decades since I last purchased a single quart bottle for my vehicles. I even buy the gallon jug of Rotella T6 5W40 for my two push lawnmowers. It's oil I change every two years.