Ask Honest John

Most recently answered performance fuels questions
I have followed your site for some time and have many a time heard the advantages of Premium diesel (or even branded diesel) over supermarket diesel. I myself have experienced the improvements. My question...
Having followed your advice, I this week purchased a 2010 Mazda MX-5 2.0 Sport Tech RC six-speed, which I am very happy with. The manual states to run it on premium unleaded - is there a particular fuel...
My Mazda 5 1.6 diesel has started to cut out. The car does a 30-40 mile journey once a week and longer ones once a month. I also use Shell V-Power once a month (there's no garage near), so I would hope...
My Fiat Panda is three months old and I have been back to the garage several times. If I travel over 100 miles it splutters, like dirty petrol. The warning and engine lights come on and I'm now fed up....
I have recently had a problem with my Hyundai ix35 (12 reg/25,000 miles) regarding the fuel filter clogging up in cold weather. The car came to a halt after losing power and the garage advised that the...
My BMW 3 Series Touring sometimes misfires and starts jerking (kangaroo style), on a trailing/light throttle about 1500rpm as though its in too high a gear when its not. BMW have queried what fuel I...
You frequently encourage readers to use Shell Nitro+ diesel, and on a recent trip that went through Edinburgh I brimmed my tank twice with the fuel, and I felt a marked difference. Sadly however, where...
Last week you advised against supermarket petrol. I have long been confused about this issue. I have been told by one chap who was 23 years in the oil industry that refineries supply to large numbers of...
If my understanding is correct, Shell V-Power Nitro+ and Millers Ecomax fuel additive (when added to regular Shell diesel) both claim to achieve the same objective. However, Millers Ecomax additive works...
Is standard or higher octane petrol used in EU economy testing? And is it worth paying the extra in an ordinary car?