I have used it over the years also ATF !! I'd just add a half litre to your next fill up !! It realy won't make any noticeable differences but does seem to clean the injectors and valves etc !! I've stripped heads after running either of the above and they are usualy cleaner !! Sometimes!!!
cheers for that ,i just thought id ask the question cos wasnt sure if the lad at work was just takin the **** ,i have mixed petrol in before in the old series engine to reduce smoke for the mot which works ok