Dear Doc, 

I own a Volkswagen Passat 2.0 TDI (138bhp) with the Euro-5 engine which, although it is now just over five years old, has only covered just over 34,000 miles. We very rarely use it for journeys of less than around five miles, and most of the miles have been clocked up on journeys between 20 and 200 miles, mostly on A-roads and motorways, including about 1,200 miles per year towing our caravan, which I presume usually gives the engine a good workout. I very rarely use supermarket diesel. Without giving too much away, I started driving in an era when it was customary to put a couple of shots of Redex into the tank, when filling up with fuel, in order to keep the engine clean, but this practise ceased rather a long time ago, presumably because of improvements in motor fuel quality. However, whenever I see adverts for fuel additives, such as on page 40 of the Christmas edition of Diesel Car magazine, I wonder if I should perhaps be using one in my car. 

I really enjoy driving the Passat, because of its comfort and economy, and I want to keep it as long as I can ñ particularly now that the government’s policy towards diesel has reduced its value significantly. So, in order to maximise the life of my Passat, would you recommend that I start using a fuel additive and, if so, which do you recommend? Bearing in mind that I have not used any additives to date, would you expect the engine to emit a bit more smoke initially as the additive cleans any residues from the engine and exhaust system? Your advice would be much appreciated. I always enjoy reading your section of the magazine, so keep up the good work! 

Richard Adams, Cheltenham

Hello Richard,

Nice to hear from (hopefully) sunny Cheltenham. It is one of our favourite towns. Yes, I well remember Redex! Years back (“without giving too much away” as you say!) I used to run a Velocette LE ex-police “Noddy” motorcycle, on which I regularly travelled from Norfolk, where my parents lived, up to Huddersfield, where I was at college. I must have been hardy in those days of my youth, as I did the run home in the depths of winter! Well, I spent a spell of six months during my practical education at a cement works near Ashbourne in Derbyshire, this being the industrial experience part of my “Sandwich Course.” And very interesting it was too, and I actually ended up doing a spell of quality control shift work in the chemistry laboratory. 

Anyway, I came off the night shift one morning and ran down into the garage in Waterhouses village to fill up the Velocette and decided to give it a treat with a shot of Redex. Well, of course the LE was a flat twin four-stroke (side valve, 192cc) and maybe I was a bit tired, but what I had gone and put in the tank was not Redex additive, but a rather large shot of two-stroke oil! So, for the next 150 odd miles, I left a trail of blue smoke behind me wherever I went. It was a wonderful bike, of which I had such fond memories that back in the mid-90s I got together the bits of one from various different sources, and rebuilt it, with a registration number that came with the engine, and was on a Metropolitan Police LE machine originally. I digress, as I do too often, but hopefully those memories will amuse you!

I have used Millerís Diesel Power Ecomax (and essentially the same product with its earlier names) for many years, along with other additives, from Wynnís, and Fast Exocet (now owned by Millers Oils). It costs about £10 to £12 for a 500ml bottle, and at the standard dosage of 1000:1 it costs you effectively only 2p to 3p a litre on your diesel costs. I have often used a double dose with a new (to me) car, to give it a good start in its life with me, although it may not be a good thing to use on a brand-new car possibly though, as it might lengthen the engine loosening up. It is best that you maybe look up the Millerís website to see the full claims for the product, which include a boost in cetane value, along with detergents and combustion enhancers. At a double dose, which I would suggest you try first, for two-to-three tankfuls maybe. At that dosage you are still only paying half as much as the premium for costly stuff like BP Ultimate and Shell V-Power (up to 8p to 12p a gallon over standard diesel) where half the money goes in advertising and whatever. Alternatively, Wynnís make a very good range of not dissimilar additives, although their large range of additives is a touch confusing, and there’s also a Redex diesel fuel treatment available, all either online, or at Halfords. I would not expect you to see any smoke, with the way your car is usually driven, but it might just feel a bit more sprightly, and you might well notice some fuel economy benefits. As I have said, if you do take up the idea, a few tanks at a double dosage might be a good start. 

Please let me know how you get on, as I would much appreciate the feedback. 

Best regards,

Doc Diesel