Wd 40 lubricates, but not in the traditional sense of the word.
It lubricates but also dries out items. it's hard to explain. I like old fashioned grease and oil, stays there and does it's job.
Simple experiment spray wd40 into some bearings of the bearings on your car, some nice expensive one's. give it 2 weeks and they'll be F'd. Then put some put some copper slip in the bearings you have had toreplace and they'll run and run. found this out in my skateboarding days, buggered bearings are not good !
wd40 drives out dirt, grease, oil etc...., but you are using oil in the fuel. therefore common sense says use something that does not leave a residue. using wd40 leaves a residue and arguements sake that gets into your engine, this then could effect the lubrication performance of your oil. i could be wrong and sometimes i am. just i wouldn't use it. Oh and if you get wd40 on a new body shell prior to painting it....... go get a new one.