Which is better for my Subaru, the Subaru Premium Synthetic product as used by Subaru dealers or Mobil 1 products such as Mobil 1 5W40?
It might surprise you, but the Subaru Synthetic is made from a “Group 3” base stock. This means that the based stock is a highly refined mineral oil not fully synthetic like Mobil 5W30, and as you know, full synthetic base stocks provide superior performance in comparison to mineral base stocks.
This superior performance includes:
- Higher Viscosity Index – This prevents oil becoming too thick at low temps and too thin at high temps – This reduces engine wear, especially at temperature extremes.
- Low temperature performance – Keeps oil flow at start up – This means oil reaches critical engine parts more quickly to reduce engine wear.
- Lower volatility – Reduces oil burn off – This reduces oil consumption and the need for frequent top up.
- Lower traction – Due to the more consistent molecular structure of synthetics, there is less friction within the fluid – This leads to greater efficiency and lower oil temperatures.
- Increased Oxidative Stability – Resists breakdown and attack from oxygen molecules – This slows down the rate of oil thickening and minimizes engine deposits and varnish.
This does’t mean that the Subaru Premium Oil is a bad product – far from it. It is also widely recognised that good quality mineral based oils are ideal for new engines being run in, so need to rush out and change the oil in your new Subaru (or other car). But after 10,000-15,000kms, you really should be using a fully synthetic oil, and we at MRT only use Mobil 1.