As long as it is thin enough to flow at low temperatures and thick enough to perform satisfactorily at high temperatures where you live. 6L of 5W30 will perform correctly up to -25 degrees C and in 75 big round years of driving I've never seen those temps. Manky filter-change it !
Good glad you're sorted Dave. To help your understanding on your model all the work is high pressure vacuum suck not blow as in a electromechanical fuel pump in the tank. At that point there is enough [#5 having just enough fuel in stock up front ] to start the car. If you get any air in or a vacuum out that displaces pressure and fuel. If your car starts and runs with the use of the primer button you have as you have found just that air in or a vacuum out on your low pressure side.
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