XD3 Esso 0-30 or 0-40 syn, this HDEO is a great engine cleaner. $4.00 per litre there about at Esso bulk. $5.50 litre at Walmart for 0-40, bulk station best bet. It will clean an engine in two to three OCIs. Oil will come out quite dark first few OCIs, then use regular and keep engine clean.
Father's Sentra was bought with 150K kms, after 3 OCI's with XD3 syn oil his engine cleaned up, oil started to come out clean on subsequent OCIs and gained 2 mpg, smoothed out and more power. TBN of 12.2 on XD3, will clean it up inside.
My 05 X-Trail QR25DE gas engine will always be perfectly clean, used XD3 from start new, dirt blonde on OCI. My 92 Dodge Cummins diesel which I bought with 150K took about 3 OCIs to clean it up too, now oil is dirt blonde on each OCI with constant XD3 use.
Nice gentle natural clean up in my families experience using it on gas and diesels, it is a CI-4/SL oil.
Cyprs