Diesel drivers are still overpaying on fuel by as much as 20p per litre according to the latest RAC pump price report.
It comes as a separate report by consumer watchdogs at the Competition and Markets Authority (CMA) suggested supermarkets may be to blame for recent high fuel costs.
They found last year's supermarket pump prices appeared to be around five pence per litre more expensive than they would have been at 2019 percentage margin levels.