5 Star is one of the most popular tuners for motorhomes. It changes the shift strategy and how the ECM reads the throttle positioning sensor which might change fuel mix and timing a bit under certain circumstances. And no, it will not harm the engine. You wont get any significant (measured on the dyno) gains in HP or torque but you will get a slightly noticeable improvement in acceleration and drivability, especially on grades, where it will help eliminate some of the hunting these drivetrains suffer from. Also the guys at 5-star are very customer service oriented and will work with you to tweak the parameters a bit and create your own custom tune at no additional charge. And you can easily return it to stock for trips to the dealer or for smog checks.
I’ve added 5-star to two coaches. On the first, a 2010 E450 24’ C- (Phoenix Cruiser) I spent a lot of time and around $2000 trying to eek out a little more performance. I changed the air filter and plenum (K&N), and post cat exhaust (Banks) and added 5 star. The combination allowed me to utilize 4th gear more instead of the thing immediately going to third on grades. For me this was an improvement but it also required lot of throttle feathering, not using cruise, and manual shifting. I did some testing and this cut about three seconds off my 1/4 mile time (from around 22 to 19 by my non-racetrack calculations) which equated to better on-ramp and passing performance. With a light load and not towing the thing was actually fairly peppy.
The other was a 2010 30’ F53 (Newmar Bay Star). On this beast, I just added 5-star. It helped some but not enough to make any real difference. That coach weighed a lot more so the same changes in tuning weren't as perceptible. Basically it was a delivery truck dressed up like a coach and it was beyond hope for driving comfort and performance. As a leisure vehicle it was fine, but it took a lot of adjustments in driving style to make it enjoyable. Nice camper though.
Also on the Phoenix, the intake was LOUD! When that thing was pulling a grade in 4th (where previously it would have been winding out in third) it was really breathing. So while the engine wasn't “screaming” (a common complaint from folks who haven't figured these things out) at 5000 rpm, the intake was howling and conversation wasn't any easier. But it was faster, an improvement I primarily credit to the Banks and K&N. As with any engine, making it breath better is probably the most meaningful thing you can do these days. Its also the most expensive and difficult, and Im not sure the K&N part added much perfomance. I think it was primarily the exhaust. It also sounded better (to me) but thats pretty meaningless.
One of the problems with post 2007 Fords is the elimination of the “OD OFF” button in favor of tow/haul (useless and unnecessary IMHO). This eliminated the driver’s ability to manually select 4th gear. I found this irritating and limiting and since I wont willingly run these rigs at 5000+ rpm (even though the experts say this is just fine) I had to just throttle back and take the hills at a lower speed (less than 45mph) in 3rd.
My $2000 investment, and more than a few hours efforts, enabled me to use 4th on the mild and moderate grades where previously it would have required 3rd, but in the final analysis, it wasnt really worth it. Also to install the Banks exhaust I had to cut out the old system as it wouldn't come out in one piece without removing the axle (didn't want to do that). So faced with this prospect, you are committed when you break out the saws-all - something to think about. Its cheaper and easier to just let it go to third and run at 45 when you have to, and live with it. Since its supposed to be travel and leisure anyway, getting there a half hour later after a full day on the road shouldn't be much of an issue.
A note on tow/haul: I know a lot of people really believe in it, and some get pretty emotional discussing its attributes, but it is just a shift strategy. You can do the same thing with the shifter (if you‘re paying attention) and you could do it even better IF you could shift to 4th at will, up and down. In my 2017 F250 I can manually shift to any gear (in “M”) and lock out any gear in “D” with the little rocker switch gear selector on the shifter. These abilities eliminate any hunting, and provide the driver complete control of the transmission. For me this is a much better arrangement than a design team derived, one size fits all attempt at making the vehicle think for the driver.
