I presently use Diesel-Kleen, gray bottle, in my 02 Golf, I have since first fuel-up. The engine is a little quieter and fuel economy is slightly better, and it adds some lubrication for the IP. I am considering an '12 Passat, if I get one, I will be using the Opti-lube XPD. If you read the scar wear tests on the ULSD, most fuels barely meet the minimum requirments for lubricity. The only one that I have read that easily meets the specs is the fuel from Irving, and that is still not that great. Because of the HPFP issues, and the associated costs IF something goes wrong, which seems to be rare, I will be using an additive as cheap insurance. Also, because of the HPFP issues, I am also going to see if the CAT 2 micron fuel filter is still available and if it will fit on the Passat.