contrabandit

lead replacement additive and a mixture of 20-1 would probably solve your problems

just a bit it's like comparing a shovel to a JCB and asking what the main difference is , aJCB can handle a lot of dirt and can really shift it where as a shovel can only handle a bit , is slow and hard work.

you have to allow for the oil filter being empty of oil after an oil change especially if you changed the filter as well , which is allways reccomended to do so, or the clean oil is just running through a dirty oil filter.if you run engine the filter will fill with oil and the level will go down.