OP, theoretically, you should never be using the adapter because it makes a mess and there are enough "car" pumps out there. In my 2 years of diesel cars and driving all around the Northeast, I've never run into a station where the pump wouldn't fit. BMW does take it one step further by preventing the wrong size from fitting. If it doesn't fit, move on. Don't use the adapter

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2011 BMW X5 xDrive 35d Vermillion Red Metallic/Black Nevada Leather
Options: ZCW, ZPP, ZRC, ZTP, 300, 386, 496, 4AB, 6FL, Combox, LED Coronas. 04/11 Production