DOUBLE VS, SINGLE OVERHEAD CAM-
In 2013, the Subaru Outback changed engines to a double overhead cam and timing
chain but only gained 3 horsepower. Unfortunately, there's percentage of cars that burn
excessive oil with the newer 0-20 weight. Is this really more efficient or just more
The zero weight oil has to do with the government mileage test which starts with a cold engine. The zero weight helps the mileage for the first few seconds but after that does nothing. Most owners could not tell the difference in mileage without sophisticated test equipment under controlled conditions. It is my understanding that the problem is two fold, these engines use low tension oil rings to reduce friction and thin oil. You can use a heaver oil such as 5-20 or 5-30 synthetic on newer cars and there should be no warranty issues but you can double check with your dealer on that. I suspect using heavier oil will help but not stop the oil consumption issue.
Great job explaining this, the EJ 25 series engine used from 1989 to 2012 in two phases on the Subaru Outback was designed for 5-30 oil. In 2013 , the Outback got the new FB series engine with the synthetic 0-20 viscosity and all of these issues came to light..
0w20 and 5w20 oil is the same viscosity when the engine is warm. The second number (after the "w") is the oil's grade or viscosity. One is NOT "heavier" than the other. Using any oil other than what is recommended can cause engine damage in some unusually cold temperature events (pretty rare, but happens). This has to do with tight tolerances of the valve train and lack of lubrication at start up. I have actually seen camshafts seized in overhead cam engines some years ago due to wrong oil being used during -20F temperatures. These engines had 10w40 oil in them versus the recommended 5w30. For a good read on oil go to http://www.bobistheoilguy.com/putting- the-simple-back-into-viscosity/
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