Thanks Larry. The issue about running the engine and generator monthly up is a very good one. My recommendation, based on information from most diesel engine manufacturers, is as follows:
1) If practical, every month or so it is advisable to start your diesel engine and then drive your coach for 40 minutes to an hour. This will provide the greatest benefit to the entire coach. If you can not drive the coach to let the engine warm up to normal operating temperature, you are better off not starting the engine at all. Just running the engine at an fast idle does not put a load on it and will not allow it to warm up properly. Running the engine at low idle will result in more damage than benefit, including increasing the potential of oil buildup in the airbox. If you can take the coach for a run, you are benefiting the engine, the transmission, the air system, the brakes, the tires, etc. One of the reasons that over the road trucks get longer life out of their engines than RVs is that they don't sit without being started for months at a time. This advice applies to ANY diesel powered coach, not just Detroit 2-strokes. Now to the issue of cold weather starting specifically. If you keep you coach in a heated building, the issue is irrelevant since above 40-45 degrees the engine should start well with decent batteries and after allowing a couple of minutes to allow the air pressure to reach 120+ psi, you are ready to start driving the coach slowly at first to let it warm up. When the engine temperature reach normal, then you are ready to 'drive it like you stole it'. If the coach is kept outside in very cold weather and at least 15 amp electricity is available, turn on the block heater (nothing else including the battery charger unless you want to trip the breaker) 4-8 hours in advance to avoid additional engine wear at start up. But, you ask, what if the coach is stored outdoors in very cool temperature and no power is available to the site? I would wait for a warmer day to try to start the coach. A coach with a Primus or Aqua-Hot system is capable of warming up the main coach engine much faster than an electric block heater so you may have time to fire up the Aqua-Hot or Primus unit on diesel/propane and let it run with the engine preheat on for an hour or so to warm the engine before taking it for a winter spin. If there is ice on the roads, wait for a decent day.
2) Running the Generator. The generator most commonly used with the diesel powered Newells are powered by diesel engines also. Here there is an interesting difference. The small diesel engines that power most of our generators are equiped with glow plugs to help them fire up in colder weather. Generator manufacturers recommend that the generator be run for at least an hour a month under load. Accomplishing this is much easier than warming up the coach's main engine. First, you don't need to go anywhere, unless you are in a warm building where the exhaust fumes from the generator might be a health issue. Use your glow plugs to pre-heat the combustion area (typically 30-45 seconds, read your owners manual for specifics since many different diesel engines have been used in gensets over the years). Fire up the generator and as soon as the the generator is running smoothly, start loading the generator by turning on electrial devices one at a time. If you have an Aqua-Hot, you can fire up the Aqua-Hot on electricity and put a nice 240 volt load on your system. If you don't have Aqua-Hot you can turn on your electric heaters in the coach to put a load on the genset. If possible put a load of approximately 50% of the rated capacity of the genset on the generator during the time the generator is running. When it is time to put the generator back to sleep, turn the electric loads off one at a time to give the generator time to adapt to the reduced loads, then let it run for a couple of minutes with a very light load, then shut it down. Of course, if you are taking the coach for a nice drive, you can accomplish both at the same time.
3) Now to your second question regarding oil in the air box. If you do not have excessive idling, it is doubtful that you will have much oil in the air box. DD 2-strokes have air box drains with check valves in them. Under low pressure, such as generated at low idle, these valves open and allow oil to flow out of the heads, typcially into a drain canister. At higher pressures, typically above 800-900 rpms, these valves close. The air box drain canister should be emptied at least annually. There should be a petcock on the bottom of the canister. If there is almost a full canister of oilly mess in the canister it has either been a LONG time since it was drained or you have a potential problem that needs attention. For those who haven't seen this canister, it is located on the driver's side of the coach, along side the engine/transmission near back of the rear most tire. It looks like a black fuel filter with a petcock on the bottom and has a pair of small (~1/4") tubes on the top that run up to the sides of the cylinder heads. Draining this canister likely saved Tom from destroying his engine when he found it full of coolant indicating a major problem. If you don't feel comfortable draining this canister, most truck repair shops and certainly Newell will be happy to drain it for you. Remember that in cold weather, it will take a while for the thick oilly substance (it also has some diesel fuel residue in it) to drain out.
If you are regularly draining the air box drain canister and not finding excessive amounts of oil in the canister, you are unlikely to find much oil in the air boxes. If you want to be sure, there are small air box inspection ports on the sides of the cylinder heads that can be opened to view inside the air boxes (each cylinder head has an air box). These look like little rectangular boxes screwed onto the side of the cylinder head above the exhaust manifold. Remove these inspection ports when the engine is shut down.
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