Who knew??? Canola oil, better then lithium grease!

The problem with vegetable oil is the smell when it will start to go rancid.... no ?

+1
Lubrication seems more necessary for those that don't have things properly calibrated and moving smoothly.

Never noticed any rancid smells in my other applications I have used it.  Also my SD is calibrated to rediculous levels of precision.  I tension my belts using a system I developed with a digital pocket scale that is capable of .1 grams +/- accuracy.  In other words my y axis belts are so identical it's not funny, and the HDPE block adjustments I use a c clamp that allows me to dial in the pressure they exert to a very specific no-wiggle, but silky smooth glide... Anyhow point being I don't use lube because of lack of calibration.

I've noticed some like to add copious amounts of grease/lube when they use it thinking the more the merrier.  Unfortunately, and especially with grease, low torque, high precision applications (solidoodle definitely being low torque relatively speaking) grease can cause some serious issues.  But of course the Z axis is not low torque since it's less about speed and more about precise movement, hence I am all about the z-axis being all greased up, and does seem to help with noise.  Anyway my point was that in most lubing applications I tend to be as light as possible, too much low viscosity oil based lubes are a dust trap that is not terribly desirable. 

So lubing the x and y carriage rods just really decreases friction, and helps put less strain, on motors and components.  Like a car it's just going to help extend the lifespan of your system. I admit it may just be the overly meticulous/cautious side of me.  But there is something about an ultra silky smooth no wiggle x and y axis that make me feel warm and fuzzy on the inside, even if it's not required. But I think even if there is no wear benefit I think it would help reduce jerkyness when the axises change direction during a print.

I agree with you that going rancid is not an issue and in no way would I suggest not lubricating.  I have seen instances where there is so much grease on everything that it is a huge mess.  I just bought a used SD recently that the guy sold because it wouldn't make even sort of a circle   That thing had so much grease on it I couldn't believe it.  Once I cleaned everything and spent a little time calibrating and adjusting it worked perfectly.  FWIW I use LPS 3 I have never had any problems with the plastic degrading.  Just spray a little on a rag and wipe the rods.  I only do this if it is needed.

Kind of like when I suggest to Noobs to use Saran Wrap for a temp enclosure.... It's in the drawer next to the stove