MPG in town great, motorway terrible

[Horse6]

Hi everyone, just bought an A4 TDi 2.0 Quattro 2015 B8, bizarre findings….mpg in town, mainly A roads and taking it easy I’m getting roughly 45/50mpg…..on the motorway with cruise on at 70mph I’m getting only just 40 mpg. Just purchased and from MOT history looks as though the car has only done 3,500pa the last couple of years and I would surmise that would have been short journeys. Not sure if DPF would be clogged, I’m by no means an expert. No fault codes from 2 separate independent garages. I’ve added a STP injector cleaner but only used 1/4 tank so not enough to notice a difference if I ever will. There is also a drone which is especially noticeable on the motorway, not sure if it’s just the exhaust noise as standard or there is an issue, booked in on Saturday to get it checked. Any help would be appreciated and I will provide feedback with any progress from recommendations as per new member guidelines. Many thanks in advance. 

[Stevey Y]

35 minutes ago, Horse6 said:

Hi everyone, just bought an A4 TDi 2.0 Quattro 2015 B8, bizarre findings….mpg in town, mainly A roads and taking it easy I’m getting roughly 45/50mpg…..on the motorway with cruise on at 70mph I’m getting only just 40 mpg. Just purchased and from MOT history looks as though the car has only done 3,500pa the last couple of years and I would surmise that would have been short journeys. Not sure if DPF would be clogged, I’m by no means an expert. No fault codes from 2 separate independent garages. I’ve added a STP injector cleaner but only used 1/4 tank so not enough to notice a difference if I ever will. There is also a drone which is especially noticeable on the motorway, not sure if it’s just the exhaust noise as standard or there is an issue, booked in on Saturday to get it checked. Any help would be appreciated and I will provide feedback with any progress from recommendations as per new member guidelines. Many thanks in advance. 

Hi is it petrol/diesel how many miles on the clock, you wont really notice any difference from the additive at this early stage, the best additive I have discovered so far is Dipetane which can be used with either fuel.

Steve.

[Horse6]

Thanks for the reply Steve, it is a 2.0TDi 187 bhp engine. Will check out the Dipetane and use in the future. I’m just perplexed as to why the mpg would be great around town but noticeably worse on the motorway….never had a car exhibit this before. I mainly do motorway miles so need/want to get to the bottom of a potential solution. Thanks.