wrote

My mechanic likes to use Castrol extended and change oil
every 5000 miles. I have alway s used Pennzoil 10/30 and
changed oil every 3000 miles. which one is right?

Neither depending on what sort of vehicle it is,
where you are and how you use that vehicle and
what the manufacturer recommends oil change
wise and how old the vehicle is.

Or both of us right? Whaddaya think guys?

I gave up thinking, it just makes my head hurt.