Chain lube

hi
i've been looking for some good but cheap chain lube. all the stuff is crazy expensive. 7 quid for 100ml is freaking much.
which one do you use?
i read one day something about using motorbike oil here on the forum.
L
that was me..
I ride my bike offroad 6 days a week twice a day on fridays...no chain lube seems to stay on the chain..i have tried everything..so I buy a 500ml bottle of 15w40..motorbike oil and put it in to a small oil bottle..
just make sure you give the old chain a good wipe to remove the excess, then use the rag to wipe clean the bike after you clean it..and give the exposed bolts a good cleaning..
I have to say though I was stuck and bought some Halfords stricky lube one time..it worked a treat but you don't get much of it..
Bear in mind that my bike gets severe abuse and constant riding, so normal oil is not got going to stay on the chain anyway..
Spray oil is great for using with a lighter to slaughter spiders !!