Don't use any of that crap, fuel additives, injector cleaners, octane 'improvers' etc. None of them work as claimed and they cost a fortune. I notice that no car manufacturer will put their names to these products.
I had a diesel toyota corolla estate for 5 years and my local airedale toyota garage advised me to use additive .they said they sold gallons to taxi drivers not sure what it was called but it was sold by toyota .i think it did improve mpg slightly and never did any harm to the engineandmost have lubrication inthe engines best freind. shell v -power i am told is very good it costs more but will deliver better performance and mpg this already has additives in .
I found recently a research made by german institute (engine developement) and they refering to bad influence on diesel engines caused by modern specs diesel fuels. Actual fuels are less "greasy"because of sulph lack. At the end of the research they say that the only improvement can be done is to mix diesel with 1/200 2t oil. It maintain a cleaner fuel system, reduce fumes, compatible with catalitic converters and PF, and not the least, a 3-5% fuel economy.
waste of money.
Also, if you are under warranty don't add anything. If (when) the fuel pump fails and fills the whole fuel system with swarf they will try and use it as an excuse not to fix it. (Yes they will check the fuel)
If you read round the diesel forums though, they are adding 2-stroke oil when they fill up in an attempt to lubricate the fuel pump and offset the effects of biodiesel.
Just the technical abbreviations are often not understood by everyone. I should have worked it out: 2T is on the label of the bottle of 2-stroke oil I have, I'm old, so I write mix ratios as 200:1 (which is actually backwards meaning 20 litres of fuel to 100ml of oil.