Sorry don't want to preach to the already converted but for those doubters it is absolutely not a placebo effect.
Spend some time and do some research - Shell V Power diesel is not a marketing gimmick. It's a Gas To Liquid synthetic fuel. Chemically developed and perfected in a lab, then has the additives added to it. It not only has a better cetane rating than any other diesel out there but it's also continually cleaning your engine and fuel system as it passes through.
I mod on another large car forum and we've had this debate a number of times... more of than not when our members have switched to VPD they've all come back and just said 'wow'.
BP Ultimate is just reguarl diesel (derived from the petrol distillation process as a by product of petrol) and has additives added to it.
Shell VPD is genuinely unique.
Can't guarantee it will give you better MPG but there's a strong possibility it will, and make it enough to justify the premium. What it will do is make your engine noticably quieter, more responsive and emit less smoke. If your car is remapped, you'll almost certainly feel the difference.
You might need to run a few tankfulls through before you notice the difference. My brother bought his GT TDI 150 this weekend and I made him switch to the stuff straight away, he even commented on how better it felt after 100 miles.
Look at the fuel in a jar, it's closer to petrol than diesel!
