By (un?)popular demand, here are my tips for how to make your piston engines last, and not. This goes into some of the varying ways of keeping engines happy while they're sitting in the hangar, waiting for you to let them unleash their power and break the surly bonds of earth. We're not talking about running your engine. 1) Preheating Preheating is good for your engine. I personally recommend a full Tanis or Reiff heater setup. My personal preference is Tanis, as I believe they sell a cleaner product, and I also like the fact that they place heat right at the cylinder head (where it's most needed) vs. the cylinder base. Disclaimer: Tanis donated two full engine pre-heater setups to Cloud Nine for the 310. But, we asked them for a donation because we believe in their product. The Aztec had a Reiff setup, and it worked just fine, too. I recommend getting both the cylinder heaters and the crankcase/sump heaters. I do not recommend the 100W lightbulb. Although unlikely, this can potentially cause a fire hazard if there is an oil leak, and many of these engines do. I also do not recommend use of a "Red Dragon" or similar torpedo-style heater. Yes, this will make the outside of the engine and the cylinders warm to the touch, potentially even hot. Aside from the fact that these heaters may produce too hot of an output that can cause damage under the cowl, they do not heat the core of the engine. Think about this as the difference between putting a frozen casserole in your oven (which I often do since I forget to take it out of the freezer) and setting it at 200F vs. taking a blowtorch to it. The latter will heat it up faster, but if you simply wait until the outside feels warm (which won't take long) and put a fork in it, the center will be frozen. That is exactly what will happen to your engine. One cold night in Canada about 17 years ago, the previous owner of the 310 had the engines pre-heated with a torpedo-style heater. The engines started, and then one engine spun a bearing. Fortunately he had a spare engine, or he would have crashed and likely died. There are different theories on when to plug in. I would say definitely below 40F, and any other temperature has benefits still. So this depends on how much you want to go to the trouble of plugging in. DO NOT PLACE YOUR PREHEATER ON A TIMER! Placing your pre-heater on a timer will cause the engine's temperature to fluctuate, allowing water to condense in the oil, accelerating corrosion. You hear an A&P tell you that pre-heaters cause corrosion, this is typically the reason. In a very severe accelerated test, we were pulling about 4oz of water out of an engine every day. When the engine was torn down (after only a small amount of run time), there was corrosion on a number of internal parts. Again, this was a very severe case, but remember your engine will be expected to last a number of years. Instead, plug your engine heater in the night before you intend to fly. Leaving it plugged in all the time isn't a bad option, either, and Tanis says that there's nothing wrong with doing this. Covering up your engine helps keep the heat in the engine, and keeps it warmer as well as help warm up faster. There are varying forms of covers. While the custom-fit ones that cover up the propeller and spinner are the best (remember the propeller and spinner serve as a big heat sink from the crankshaft). However, I don't think that the natural convection that would come off of the prop and spinner matter much. So we just use sleeping bags. Seems to work well - even in -20F outside, the cylinders and oil were a happy 100F. 2) Dehydrators I haven't worked much with engine dehydrators, but we are going to buy some for the 310. The theory behind a dehydrator is to make sure the air inside the engine is as low humidity as possible. This can only help prevent corrosion, especially if you live in a climate that's humid. Dehydrators have a secondary benefit, as well. They will expel the gasses in your crankcase post-shutdown out of the engine. These gasses are not only very high in moisture, but also have corrosive combustion biproducts in them. Not something you want to keep around. They can either be attached through the breather to pump air out through the oil inlet or vice versa. I prefer pumping air out of the breather, since that gets the corrosive gasses expelled from the area under the cowling. There are two types of dehydrators - the desiccant style and the dehumidifier style. The former just uses desiccant pellets to absorb moisture, the latter is effectively a dehumidifier. I've gone back and forth on which one I like better, but the desiccant style is certainly cheaper, and I think that will be what we ultimately purchase. 3) Oil and oil additives What oil you put in your engine matters. In one test I saw that looked to specifically identify the ability of oils to protect against moisture. The test was severe, but found that Philips XC 20W-50 by itself had very poor corrosion resistance. Philips XC plus CamGuard or Exxon Elite both had excellent corrosion resistance. As those were the only oils tested, I can't say anything regarding corrosion resistance on the various AeroShell oils. A theory I have heard is that, if your engine sits routinely, it is wise to use straight-weight oil rather than multi-viscosity. The theory is that the straight weight oil will stick to the internal parts better, and so you won't develop corrosion as quickly. This theory makes sense, however I believe that the improved lubrication performance from a multi-viscosity oil outweighs the potential negatives, especially if you are taking other precautions to warrant against corrosion. One point of note here is that Exxon Elite (as well as Aeroshell 15W-50 and 100Plus) all have the Lycoming "snake oil" additive that is required for certain engines. In Lycomings, this additive is effectively a friction modifier and doesn't hurt anything (especially if you have an H2AD, for which it is a requirement). In Continentals, it can impact the clutches in your starter adapter (unless you have a Continental that doesn't have a starter adapter). While there is some debate over whether or not it truly impacts the starter adapters, we intend on using Philips XC plus CamGuard in the 310's Continentals. So if you want your engine to last: get a full pre-heating system that has a heating element for each cylinder, as well as heating elements for the crankcase and oil sump, cover the engine, and plug the heater in the night before you fly (or leave it on all the time). Don't forget to put the covers over the engines. Buy a dehydrator, and use Exxon Elite or Philips XC 20W-50 with CamGuard (and potentially at least certain variants of AeroShell). If you want your engine to corrode and fail: put your pre-heater on a timer, then let your engine cold soak and use a torpedo heater on those really cold days to just get the cylinders warm enough. Never bother covering it. Don't use a dehydrator, and just use straight Philips XC 20W-50. Or, for that matter, just use vegetable oil. Now the real question: how much does any of this really matter? It is difficult to answer that with a great deal of certainty. I've witnessed and performed a number of extreme tests that, as you would expect, produce extreme results. Most of us don't live in extreme worlds, and our engines don't, either. Corrosion is something that occurs over time in these cases. I have seen people who do everything wrong, and their engines do tend to corrode pretty quickly and have premature failures (although not always). I've also seen people do things partially wrong, but partially right, and they have gotten good service life out of their engines. It's so rare to see someone do everything right that I'm not sure I've seen it done long enough to see a true result, and that includes how I treat my engines. That said, I do treat my engines significantly better than most, and have gotten good service life that I attribute to it. With the 310 getting new engines, we'll have an opportunity to, fresh from overhaul, treat these engines with all the love and care that they deserve, and will get to see the results. So what should you do? The above lists what the ideal way to do things would be. Engine pre-heaters really are not very expensive as far as aircraft parts go, and sleeping bags are even cheaper (or you can buy a fancy custom engine cover). You can make a dehydrator yourself (cheap), or buy one of the commercially-available ones (less cheap). You need oil anyway, so it makes sense to choose something that's less prone to corrosion. For what it's worth, what we're planning on the 310's new engines is to continue using our Tanis heaters (plugged in the night before any trips), keep sleeping bags over the engine nacelles and stuffed in the nose plugs to keep the heat in, have a dehydrator forcing dry air through the oil filler and out of the breather, and use Philips XC 20W-50 with CamGuard.