The decision to change was based on what I understand to be slightly elevated Si (generally considered to be dirt although there can be other reasons) levels in the annual oil analysis. They are generally in the 4-6 ppm range although there have been spikes. Although the analysis report still notes these as being acceptable levels I would like to lower them. Annual engine hours (Hobbs meter) are around 250.
I would be interested to hear what values other Lehman owners are receiving. I'm using the Finning lab.