Reaching the particle emissions regulatory limits for the combustion engine is a challenge for developers.Particle filters have been the standard solution to reduce particle emissions, but filters arelimited in storage capacity and need to be regenerated, a process emitting more carbon dioxide(CO2) as more fuel is consumed to regenerate the filter. In previous research, it was found that theengine can emit large spikes in particle numbers (PNs) under stationary operating conditions. Thesespikes were several orders of magnitude higher than for the base particle emissions level and occurredseemingly at random. The source of the spikes was believed to be the cylinder-piston-ring systemand as 50–99% of the particles stemmed from these spikes, the influence on the particle emissionsmade it an interesting investigation to find the root cause of it. The experiments were performedfor different piston ring loads, locked ring positions, and different oil compositions. The resultsindicate a possibility to control the PN emissions through the experiment alterations, with lockedpiston rings having the greatest influence at a higher load. There was no clear relation between ringrotation and flutter with the spikes observed. The locked piston ring configurations did indicate thering gap not to be the main contributor to the spiking as fully aligned gaps did not result in thehighest levels of particle emissions. Variations to the oil composition indicate that a high-volatilityoil will emit higher levels of small, sub-10 nm particles compared to the standard baseline oil. Ahigh-viscosity oil instead lowers the particle emissions, possibly due to the higher inner friction athigh temperatures reducing the oil ingress into the combustion chamber. The link between the PNspiking phenomenon and the oil pathway past the piston ring was not established through theexperiments reported in this publication.