Mechanic changed oil on me :(

Thank's Im.away, but it's not the viscosity thats of concern to me, it's the other stuff. 10w40 shouldl be fine in my Jack in Adelaide for summer, seeings it started when the original mechanic put 15w40 hybrid crap in initially and it still started in autumn!

The oil probably won't do any short term harm, but yes its the wrong oil !!!
Go back to Penrite , or Castrol Magnetec, or Delvac ( Mobil )

Whoever who told you that is talking BS. Valvoline have been using Mobil base oil for years and blend in additives just like any other oil producer. You would probably never guess who else they make oil for. Same plant, same production line, different packaging & price. Go to the plant in Smithfield & have a look for yourself.

In 1991 we brought a Ford Laser brand new for my wife. It was always serviced at Ford at the specified intervals and very well looked after. The dealership had used Valvoline oil in this car from day one.
Before the car reached 40,000km's the engine had started to get a top end rattle that gradually got so bad that by 50,000km's I thought the engine was stuffed.
At the next service I changed the oil myself to a good quality brand, I think at the time I was using Penzoil. Instantly the noise disappeared and the engine is still going strong 14 years later and has never been touched. It still runs as smooth as a new vehicle.
Not one drop of Valvoline has ever gone into any of my machinery since that day and I also do my own servicing so I know exactly what quality oil and parts are going into my vehicles.

Regards,
Brett

P.S - By the way I now use Synforce Synthetic Cruiser Oil in all of my vehicles and won't go back to a mineral based oil again. 80 series turbo has 300,000km on the clock and has never been opened so I am happy.