The answer that will always be correct, regardless of the color or badging of the bottle, is if it meets the oil specs identified in the owners manual, you're good to go.New guy to the site. Love it..Anyhow here is my question ( and not wanting start a big fight) I have read all the post about oil, and alot of the members are using the Rotella oil, I went to the local Wal-mart they had the 15-40 Rotella, not syn. and that was all. It looks like it is used for Diesel engines, Not being a gear head,(lucky to change my own oil) will this work in a 2007 GL1800. Most of the post talk about the syn., they had the Mobil 1 syn. I work for a John Deere dealership, and they have John Deere 15-40 +50 that they used for all the John Deere equipment. So there is my question: will oil made for Diesel motors work in a GL1800? Like someone said when you buy a $20000.00 Goldwing what's another $20.00 for good oil. Thanks in advance..