An Oil Change and Fuel Economy

Usually, when we talk about fuel economy, an oil change isn’t at the top of the list of discussion.  The manufacturers are requiring lighter and lighter weight engine oil in all vehicles. 5w30 and 5w20 are being replaced with 0w16. I can hardly believe it, as 0w16 is like pouring water, it’s so thin.

The reason for the light weight oil is to give better fuel economy to satisfy the CAFÉ (corporate average fuel economy) standards. This standard is set by our state and requires all car manufacturers to average 54.5 MPG by the year 2025. Don’t think for a minute that the changes are going to slow down anytime soon.

Believe it or not an oil change can and will affect your miles per gallon and here is why. Us old guys always grabbed the 20w50 oil for our cars and today two of the most popular oils is 5w20 and 0w30. The comparison would be 20w50 oil will pour like molasses, while 0w20 will pour like water. Thicker oil creates resistance inside the engine, slowing down moving parts and lowering your miles per gallon. A hybrid or very high mile per gallon car can lower mileage by 1 to 2 miles per gallon.  We have observed this from some testing that we have done.

Is installing 5w30 oil in a car requiring 5w20 a concern? Yes and no. Yes, because it will affect fuel mileage, sometimes it is noticeable, sometimes not. And no, because using a slightly thicker oil will not hurt the internal engine components at all. Warning!! Thicker is not better, so please don’t use a very thick oil like a 20w50 in a modern car as that will cause issues.

Other ways car makers are working to meet the CAFÉ standards are:

  • Using lighter materials
  • Turbo chargers
  • Gasoline direct injection
  • Hybrids
  • Smaller engine size
  • 10 speed transmissions
  • Synthetic oils in transmissions

With all these changes happening today, preventive maintenance is more critical than ever. 


