Does he pay you anything plus the oil or just the oil?
Really, I suppose, it's one of those "To each his own" decisions . .
In ours, we use Amsoil Synthetic, but, if you watch it closely and change it frequently, because with a Nitrous engine, your oil is a diagnostic tool indicating the health of your engine, I don't suppose Mobil 1 is any worse or better . .
I'm sure everyone here that uses another brand have their own reasons and opinions on this . .