i have been in this business for 22 years now and still here to do service for your diesel vehicles at your yard or job site, I am a mobile service to give you the service at your time of the year thats good for your company when you are not busy. any weekends is always good or when you have to have a vehicel done for any reason. rates change due to amount of vehicles done at the time of testing. Thank you ART LOPEZ -- owner.