Burn you oil part 2.

A further refinement of using you motor oil as fuel in your diesel power vehicle. The small oil tank (1 to 1.5 gallon) would have a sensor to warn the driver when it's empty.
Based on an hours of use, the injections of motor oil into the fuel tank would be based on hours of operation instead of miles. Most interal combustion engines use hour of use as a guide to when to change the motor oil boats, planes & trains... farm equiptment.
You would use the cheaper standard diesel motor oil.
Maybe even a warning light to alert the driver as to when to change the full flow oil filter, based on 100 hours of use.