Diesel! You won't get vapor lock if your pulling up hill. The engine last longer and has a thicker block then gas. There a reason why those big 18 wheeler use diesel. If you maintain the engine you should get 300k miles or more. But diesel engines just not like the winter months. You shouldn't have a problem getting service. Of course this is my opinion.

Having owned both a gas engine class A and a diesel pusher, I can give you one other reason that none have touched on. The diesels in DP class A's are typically much more powerful than their gas counter parts. No I am not talking horse power here, I am talking torque. That is the force that actually turns the drive wheels. The largest gas engines may develop 400 foot pounds of torque, but the diesels will produce over 1,000 ftpd of torque. You will really feel that when you are pulling a grade. Diesels typically develop that torque at half the rpms of a gas engine. NO wonder they last longer. Running along at 1500 rpm for the typical diesel versus 3000 rpm for gas. It is not hard to do that math.

Also there are just as many diesel engines on the road as gas or pretty close. All those truckers get service somewhere. Now we have owned 3 DPs and have no trouble getting service anywhere and we have traveled, coast to coast and border to border. You just have to learn where to look. I have also found that diesel service places do not stay in business if they do not give good service. Truckers will not visit a place twice if they don't get the service they need there. They can not afford to because their lively hood depends on it.