Hi Cliff,
The only lube you should be using on the 420 is a little bit of white mineral grease on the racking teeth. Don't overdo it though, a little bit every 12 inches or so will be enough.
Bill P
February 2016
Nowt in the manual http://www.dolphinlifts.co.uk/images/library/documents/420_Saxon_Stairlift_User_Guide.pdf
RTFM
October 2015
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