Dipetane in a 1.4 d4d

[mpg_junkie]

Hi guys, 

Looking for opinions on the fuel additive dipetane. I have a 2012 D4D with 120,000 miles and get on average 60 mpg (UK) on my 100 mile commute each day. I have been adding dipetane to try and boost that a little over the last fortnight but my average mpg has dropped into the low 50s. I expected the additive to either give me small improvements or do nothing, I didn't expect it to make it worse. 

Does any one else have experience of this additive in a diesel engine? Thought I would give it 2 weeks to make a fair assessment but disappointed. 

Thoughts please. 

MPG_junkie