Back in the 50's in high school we separated Hydrogen and oxygen by filling 2 bottles with salt water then inserting an electrode in each then turning them upside down in another tub of salt water... turn on the dc power and it bubbled up 2 times as much hydrogen as oxygen the new system bubbles up bothe oxygen and hydrogen in the same container... JPL in pasedena CAlif normally works on space projects for the government but in the 70's they did automotive research...added hydrogen to a lean mixture and got quite an increase in fuel milage. the hydrogen makes the gasoline burn more efficiently. A lean gasoline mixture is hard to ignite. the hydrigen acts like the match to start the combustion fire. I looked at a site a while back that wanted to sell you the manual for $50 but if you read their questions and answers you should be able to figure out how to build one