hi, im a taxi driver and have been using vpower diesel for quite a while in my focus estate 1.8 TDCI... i have to say that ive noticed a very slight improvement in mpg (5-10%) but this is cancelled out by the difference in price, so im basically breaking even on cost. The real benefit for me is the fact that the engine is a lot smoother and cleaner than before. it runs like a dream and that noisy diesel engine noise has almost disappeared. it honestly runs like a new car and its done 270, 000 miles! so im about even on cost and it seems to be much , much bettter for the engine. its a no brainer for me....v-power is the only fuel i will use and believe me, during the last 200, 000 miles in this car ive tried them all. this new nitro stuff seems to be very slightly better still, so in summary my advice to any diesel drivers out there would be that you wont really save money (possibly a minimal saving), but the difference in engine health is night and day.