Several reviewers have complained about performance of the Misto. It does need regular cleaning. The more highly unsaturated the oil you use, the quicker the spray valve will clog with oxidized, polymerized oil. Varnish is just a vegetable oil selected for the ease with which is oxidizes.There is a Misto web page with complete care information at:http://www.misto.com/troubleshooting.html#HowtoInstallWhen my pump tube failed, they sent out a replacement. If you look at it carefully you will see that the pump tube does need to be handled gently.I wish their website offered a way to order replacement parts.