I'd comb through the operator's manual to ensure I was operating the controls for the opti-idle correctly. I drive a Volvo, the controls in the sleeper berth are 'weird' and it takes a bit to understand how to get it all to work OK. However, I don't even have an opti-idle capability. I did eventually find how to cancel the idle shut off and if I really need to, I shut off the idle cancel and let that puppy run. On occasion I get fussed at for high idle times. But, I try diligently to keep idle usage down whe it is feasible. But, if I gotta get some sleep and the only way to do that comfortably is cancel the idle cutoff, I shut it down and let the truck run. It is imperative I get restful sleep to be safe. I can't get restful sleep when my sleeper cab is at 90 degrees or at 40 degrees (I do have a bunk heater that works really well and will keep sleeper berth comfy when it's as low as like zero outside).