http://x.nissanhelp.com/forums/altima/2 ... p0011.html
http://www.nissanmurano.org/forums/82-1 ... hange.html
Based on the links above, could be from wrong weight of oil, bad filter, dirty oil, or low oil pressure.
1. Why do you use 'Motor Flush'? A simple drain and fill is all that is required. Can you post a link to the product you are using?
2. What brand and weight of oil did you put in? I believe the 2014 R52 required 5w30.
https://owners.nissanusa.com/content/te ... manual.pdf
3. What brand of filter did you use?
4. What is the oil level?