Which oil would be a better choice for my app amsoil 10w40 amo or amsoil euro blend 5w40? This is for my 2.1 turbo volvo, the motor is a 1981 motor with 175,000 miles on it. And because i run high boost levels i thought i should use amo because of the extra zinc and its supposed to be formulated for flat tappets, higher performance, heavy duty, and higher mileage. Which sounded about right for my car. but what do you think?