This is a very recent SAE paper on effects of oil on low-speed preignition (LSPI). In summary:
Note that lower-viscosity base oils (not the overall viscosity including the viscosity-index improvers in the finished oil) increase timing-chain wear. Therefore, 0W-xx oils should be avoided and 5W-xx or 10W-xx oils should be used instead if timing-chain wear is a concern.
- Calcium (detergent) increases LSPI events dramatically
- Magnesium (detergent) decreases LSPI events dramatically
- Increasing oil viscosity increases LSPI events (because more oil is left in the combustion chamber after the piston ring scrapes the oil), especially at higher magnesium levels
- Increasing ZDDP and moly decreases LSPI events, however effects only significant at higher calcium levels
- NOACK volatility doesn't significantly affect LSPI events
Note that lower-viscosity base oils (not the overall viscosity including the viscosity-index improvers in the finished oil) increase timing-chain wear. Therefore, 0W-xx oils should be avoided and 5W-xx or 10W-xx oils should be used instead if timing-chain wear is a concern.