Today I purchased a new 2006 Honda Civic LX 1.8 S 4cyl. 4A. During the process I told the dealer rep that I have a serious question about the 5W-20 oil that is being recommended for their cars. This is not a new subject to him. He says it comes up. He told me that although he knows the answer he is supposed push the 5W-20 for CAFE purposes, but that he would let the service manager go over this with me. He put me with the service manager and a man they referred to as a well studied tech in these matters. I explained that I do NOT want to use the thin oil but that I also want to keep my warranty safe. They had heard this before, also. They suggested that it is fine to use 5/10W-30 in the winter and went on to say that in our rather warm summers a 5W-40 will be a good choice. These gentlemen were very attentive to my concerns about warranty questions and assured me that using the 5/10W-30 in winter and 5W-40 in summer will absolutely in no way be detrimental to this engine, but they are convinced my way is a good maintenance program. They assured me that if the engine should need any service under warranty that the oil is not an issue unless something is found in the oil that caused the problem and the viscosities under discussion are not an issue. They repeated: To deny warranty because of the oil used they would HAVE to be able to show that something about the oil caused the problem, and again, the viscosities under discussion is no problem. The service manager told me he sees me as the type of person that will read every bit of the manual and will make every effort to maintain the car well. Of course, the factory fill is a 5W-20. I'm going to run it a few thousand and then I'll put in a 5 or a 10W-30 and see what the comparison might be. I'm usually not impressed with dealers, but I came away from this one with a very good feeling. There have been Hondas in my family although this is my first one. The excellent long service life of the Hondas of relatives show me this is a very safe purchase to make. And, if I were to name these people they said they would have to deny our conversation ever occurred. I came away with a very good feeling.