Viscosity, big word hey? You would have heard of this word when it comes to oil for your car. Viscosity basically means flow, then you have your heat range like 15w-40 which means the oil flow will peek at this flow at this temperature. It's important to get the correct oil for your engine. The reason why we have so many different types of oil is the way the engine has been designed. The oil pump, oil galleries etc in your engine will determine what type of oil you need for your engine to get maximum lubrication.
Brands have a lot to do with quality of that oil. It's a good idea to find the oil that works for your engine and stick with it.
Mechanic's always try and find a universal or generic oil to suit a wide range of cars, but this is no longer relevant to today's engines. But i see they still use a bulk oil to service your car. They do this to widen the profit margins, you won't notice it straight away, but you will eventually get high fuel consumption and poor performance all due to increased friction from the wrong grade of oil used. I use only Penrite or Nulon oils and the correct grade for your engine and i've (never) had a problem with my customers cars. The profit margin is less for me, but my customers are happy and their cars run so much better as the correct oils and filters are used when they service with me.
Book a service with me and i will prove a better brand and grade of oil can give you better fuel economy and better performance. My services start from $140.00 done where ever you like. Call John 0498 483 68