A lot of the 0W40 oils are simply a way of basically having a 0W30 or 5W30 bypass the fuel economy standards. Many of these meet European specifications which are more stringent than US spec for synthetic oils and are not really much thicker in tests than a 5W30. Again, they are basically bypassing US oil standards for European cars that require oils with greater anti-wear additives than US oils run. I would run a 0W40 in the engine in question long before I would consider a 10W30, especially in cooler climates.
I have run these oils myself and prefer the Mobil 1 0W40 from Wal-Mart. This oil meets the Mercedes, VW/Audi, etc. light duty Diesel standards which are way more stringent. This oil is also half the price of any other oil meeting these specs when bought in the 5 quart jug.
You may lose a few MPG when compared to a 5W20 or 0W20 but doubt it will do any harm to this engine. If the engine DOES use some oil, the anti-wear additives may shorten the life of certain emissions components such as the oxygen sensors and cat. That is why the EPA doesn’t want them in US spec cars. This is a workaround for European makes when you want to keep your warranty coverage.