The manual directs engineers to check the lube oil automatic filters, pressure regulating valves, or main bearing clearances.
There are several sources where you can find a Daihatsu 6DE-18 manual PDF: Daihatsu 6de-18 Manual Pdf
You can view digitized versions of the DE-18 Operation Manual and the Maintenance Manual on Scribd. The manual directs engineers to check the lube