T&T: Lehman Multigrade v Monograde Oil

[Milt Baker]

For a definitive answer on what should and should not be used in a 
Lehman 120 or 135, call Bob Smith or his son Brian at American Diesel
in Kilmarnock, VA, at 804-435-3107.  Bob was the co-designer of the
Lehman 135 and probably knows more about than engine than anyone alive. 
He and Brian are the go-to guys when it comes to parts, problems, or
anything else relating to these two Ford Lehmans.  Bob also teaches
the diesel class at Trawler University and frequently does highly
regarded (and entertaining) seminars at TrawlerFest.

--Milt Baker, Nordhavn 47 Bluewater


Steve Anderson stevena48 at earthlink.net wrote:

With considerable trepidation I ask the following question.  The owner's
manual for my 135 Lehman calls for a monograde oil (40W, I think).  Why can
not a multigrade oil be just as good if, indeed, it maintains its viscosity
across a wider range of temperatures?