Now I look at the details I see 1 litre of Dipetane treats only 200 litres of fuel £12/L = £60 per 1000 litres of fuel
0.5 litres of Millers Ecomax treats 500 litres of fuel £13/0.5L = £26 per 1000 litres of fuel
I have recently added Mannol Diesel Ester Additive and yet to go more than a couple of miles at 5kts MANNOL Diesel Ester Additive
1 litre treats 1000 litres , so about the same dose rate as Millers Ecomax £13/litre = £13 per 1000 litres of fuel
Dipetane was recommended to me but it seems like others are better value when the dose rate is taken into account.