2006 Sentra, ~114K on the odometer, takes 3quarts, no oil burning, or leaking.
3 years ago, I got a 12-pack of Miles Lubricants 5w-30 syn blend for really cheap, like $1.20/qt. I am on the last 3 bottles. Last week, a neighbor gave me an unopened 3-year-old 5-qt container of Castrol GTX High Mileage 5W-30 Synthetic Blend. He got it by mistake. He wanted synthetic.
I have 5qt each of Mobil 1 synthetic and Penn Plat. Both 5w-30 weights.
Before he gave me Castrol, I was planning to mix 2qt of Miles syn blend and a quart of Mobil. Planning Penn Plat in Forester that takes 5qts.
So how would you blend these oils? One quart of each for the next 3 years? Sentra gets a yearly oil change.
(P.S. - I know I am overthinking. I just want to make sure this the best strategy.)