Tuesday, December 2, 2025

We ran into this problem with my daughter's 2017 Subaru Forrester PZEV

The problem I guess began when I kept my daughter's car running here in the U.S. so they wouldn't have to rent or borrow a car whenever they returned from Europe where her husband is a Lawyer there. A friend of mine and i thought that this might might not be a problem if the car was being driven enough. However, I was only driving it a few miles a week to the beach with my dog and I only live 1 mile away from the beach. So, I guess whether you are driving this type of car or not a lot you have to change the synthetic oil frequently enough so it doesn't get too acidic and start eating away the camshaft. So now, in order to fix this car it is around 3500 dollars now to replace the camshaft. Since others of you might be in the same position with this type of car engine I thought I would share about this.

Before this all I knew was that synthetic oil can double the life or more of any car engine. This likely is the first negative thing I have ever heard about synthetic oil in some vehicles. 

 begin quotes:

 

Synthetic oil can contribute to camshaft problems in some older engines, particularly those with
flat-tappet camshafts, because its "slippery" nature may prevent the lifters from rotating properly, leading to wear
. For modern engines with roller camshafts, synthetic oil is generally beneficial, but problems can arise from using the wrong viscosity, poor-quality oils, or a lack of proper anti-wear additives. 
This video explains the importance of using the right motor oil and the problems that can arise from using the wrong one:
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Potential problems with synthetic oil and camshafts
  • Flat-tappet camshafts: In older engines with flat-tappet lifters, a combination of flat-tappet lifters, slightly tapered cam lobes, and synthetic oil's slipperiness can prevent the lifters from rotating, causing uneven wear on the cam and lifters. Cam manufacturers often recommend against using synthetic oil during the break-in period for these setups.
  • Reduced anti-wear additives: Since 2005, passenger car motor oils have had reduced levels of ZDDP (zinc dialkyldithiophosphate) due to EPA regulations. This is a problem for both synthetic and conventional oils in flat-tappet engines, which require higher levels of ZDDP for protection.
  • Incorrect viscosity: Using a synthetic oil with the wrong viscosity for your engine can cause problems. For example, a very thin oil may not provide enough protection for a performance engine, while a thick oil in a hybrid during cold starts can cause wear.
  • Poor quality oil: Some budget synthetic oils may lack essential detergents and anti-wear additives, leading to sludge and engine damage. Oils without proper certifications (like API or Dexos) may not meet industry standards. 

This video explains how using the wrong viscosity can damage your engine:
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59s
How to prevent camshaft problems
  • Use the correct oil: Always follow your vehicle's owner's manual for the recommended oil type and viscosity.
  • For flat-tappet cams: If you have an older engine with a flat-tappet cam, use a high-zinc performance oil with at least 1,400 to 1,500 ppm of ZDDP. Break in the new cam and lifters using a conventional oil and follow cam manufacturer recommendations regarding synthetic oil after break-in.
  • For modern engines: Use a high-quality synthetic oil with the correct viscosity and proper certifications. Change the oil at the recommended intervals.
  • Perform oil analysis: An oil analysis can help detect problems early. 

This video explains how to perform an oil analysis:
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56s
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