Congress wrote the speed limit laws around 1973 - 75. At the time, it was proven that new tires are about 5% taller than a used tire or one that is under inflated. So Congress declared that anyone patrolling a Interstate highway must give you 10% above the posted speed limit before being able to declare you speeding. So if you are going 60, you can safely claim your speedometer read 55, and you thought you where OK!
Yet if they clock you at 65, they will give you a ticket for the full amount, even if your speedometer read 57 at the time you got pulled over. In reality, most cops have more important things to do than pull over anyone going 62 or 63 MPH. They are looking for cars doing 80 or switching lanes to quickly, and causing accidents.
Yes you must use the Right lane, unless passing, then use the #2 lane as short of time as possible (it might take some time to pass the cars in the right lane if on a 4 lane freeway, but the law says to not drive in the #2 lane if it is a 2 lane each way roadway, except for a short time to pass. Driving in the #3 lane of 4 or 5 lanes is not allowed ever (except near a interchange) so stay out of the carpool lanes.
When not towing, it is a RV, not a commercial truck, so you can use any lane that you like. Even the carpool lanes, unless they are restricted to vehicles under 10,000 pounds GVWR. One section of the 91 freeway in Anaheim to Corona CA is restricted to Fast Pass card owners, and also limits you to 10,000 pounds, so that tow trucks on standby at both ends of the section of freeway can tow away any vehicle at any time.
Good luck!
Fred.
