Probably the most embarrassing device that I’ve ever been told to fit to a car

This content is 19 years old. I don't routinely update old blog posts as they are only intended to represent a view at a particular point in time. Please be warned that the information here may be out of date.

Last night, as is normal on a Sunday evening in my house, I had a relaxing evening watching BBC Top Gear. During the news section, Jeremy Clarkson smashed up an extremely annoying device with a light-sensor to detect when a car’s fuel filler cap is opened and warn you to use only diesel fuel.

I thought it was funny and that no-one would actually buy one, until this morning I received one in the post from the lease company that owns my company car along with a letter mandating that I fit it to the car and warning that I will be personally liable for any damage caused by any future misfuelling (I have, of course, told them that I will install the thing but have refused to comply with the liability part).

I understand why they are doing this – the AA motoring trust has produced a report which details the problem along with some interesting statistics about misfuelling call-outs. I also admit that I did previously (many years ago) accidentally put half a tank of petrol into a diesel car as well as nearly filling the tank of this car with petrol when it was new (on both occasions, I had been using a petrol car for the previous few weeks), but the lease company waited 6 weeks to send this to me and I definitely know to use diesel now!

Misfuelling may be expensive and embarrassing, but this thing is a) loud b) American c) tacky d) noise-polluting e) extremely embarrassing! If you don’t believe me, then listen to how it sounds yourself.

Add to that, I’ve had to fit this horrible thing to a car about which Clarkson wrote:

    “You’ve deliberately gone your own way, deliberately bought something that isn’t a BMW or a Merc or an Audi. And in the process you’ve ended up with something that’s not only a little bit different, but also rather good.”

[Jeremy Clarkson, Sunday Times, 13 November 2005]

I’m dreading my next visit to a filling station forecourt. As my wife said, at least it will be a talking point – let’s see if she still thinks that as she cowers down in the passenger seat pretending she’s not there.

19 thoughts on “Probably the most embarrassing device that I’ve ever been told to fit to a car

  1. At least its not just me then who has to stand on the forecourt with a siron of “Warning, this vehicle uses diesel fuel, please use diesel fuel…..”

    Unfortunately [ ;-) ] i was that embarrased on using mine, that i must have slammed the petrol cap shut, and then next time I opened it, it fell out onto the floor!

    Unfortunately it isnt broken, but its no longer attached to the petrol cap

    Good result!? – not really, I put it in the glove box, and for 2 days or so, every time I opened the glove box I had the same warning again!

  2. Hi
    Another device is hitting the market shortly, costing a fraction of the price, no electronic sound and offering a dual purpose. The device is called MagneCap and you can find more information on the website. or watch BBC breakfast on Jan 6th between 6am and 9.15am

  3. Diesel Guard sounds extremly embarrassing and annoying to NOT just the driver but other motorists around whereas MagneCap is simple , inexpensive and if used correctly will avoid you from fuelling from the incorrect pump

  4. Dieselguard was designed to provide a highly affordable anti misfuelling system. Considering that pettrol nozzles are INDEED smaller than diesel nozzles I do not see how a cap with a large hole in the middle will prevent a smaller nozzle being inserted! Dieselguard might be loud, but it is aimed at the older and hard of hearing driver, another more refined device is set to hit the market soon. Dieselguard aim to produce the top anti misfuelling system never mind magnecap

  5. From what I can see on their website, MagneCap doesn’t seem to change the nozzle size, but instead relies on specially adapted petrol pumps, to which you fix your cap while fuelling and that will only allow the cap to be fixed above the correct type of nozzle.

    On a separate note, I have reason to believe that a number of the comments on this site are actually blog spam.

    Blog spam is prohibited on this site by the rules for comments and if I see any more, I will simply delete the comments.

    On the other hand, if anybody has any real-world experience of using either Diesel Guard or MagneCap, feel welcome to post your experiences here.


  6. Hi I have experience MagneCap. I recently misfuelled my car, It was a diesel always driven petrol cars. Picked up the nozzle and auto pilot set in. Didn’t cost me as much as I thought, researched the internet and came across magnecap. They were brilliant! I am now waiting for my magnecap to be posted to me. Its so simple, cheap and I know will help me the next time auto pilot sets in. Thanks

  7. Having had the experience of misfuelling I found Diesel guard on the web and ordered and paid for one — but it has not been delivered in spite of numerous unanswered calls and e/mails. Have they gone out of business following the adverse comments on TV and in your pages ?

  8. Anonymous, I doubt that this blog has enough clout to make a company go under!

    Their website is still active, so I guess you’ve just found another reason to avoid purchasing this product…

    I still cringe every time I fill up (and more annoyingly, every time the sun shines and a little bit of light gets through the finger hole on the door covering the fuel filler cap on my Saab 9-3), broadcasting to everyone else on the forecourt that “this car runs on diesel fuel… insert diesel fuel only… commence filling diesel fuel only”.

  9. Anonymous people chosing to leave adverse comments. What did geremy clarkson do. smash it up. Maybe when the daft pillick misfuelles he will report it to the nation!

    [Dieselguard’s advertising comments removed]

  10. Kirk,
    If you read the comments above, there is an anonymous person who has left a pro-Diesel Guard comment too… I suspect that they might have a vested interest in the product.

    Also, one of the comments is from someone who tried to contact Diesel Guard after they paid for the device and it wasn’t shipped.

    You’ll also see that I left a comment referring to the blog spam that is being left here – I generally don’t censor comments (I think it’s a slippery slope that I’d rather avoid); however if you read the rules for comments you will see that I reserve the right to edit/delete comments which I believe are blog spam – I have done this for your comment above. If you want to use my website as a referral system then I occasionally accept sponsorship requests on a per-link basis and you can contact me to discuss. I should warn you though that the views and opinions expressed on this site are in no way influenced by my sponsors.

    MagneCap tried leaving a comment here and got very upset when the Google index quoted them out of context.

    Everyone else,
    The blog post above is simply a ramble about my views on the Diesel Guard product – as with much of the content on this website, it’s only an opinion and your mileage may vary. I fitted the device to the car that I use on the insistence of its owners (LeasePlan). After about 10 months the battery started to run down and it just said blurghhhhhhhblahurghhhhhh every time I filled up my tank (about twice a week). Now the battery has failed, the adhesive pad has stopped working and the Diesel Guard has fallen off. Oh dear ;-)

    I’m not sure what the improvements are that Kirk referred to – I’d be interested to hear more (like has it dropped its American accent yet?); however the main problems I had were that there was a lack of flat panels on which to fit the device inside the fuel flap on my Saab 9-3 (making it difficult to stick anywhere) and every time the sun shone from a certain direction, the light entering the fuel flap set off the DieselGuard (outside my house, driving down the street, etc.).

    In fairness, this device is probably great for car hire companies, fleets of multi-user vehicles, husband/wife whose cars use different fuels, etc. but for people like me who typically drive the same car every day it’s just an annoyance.


  11. Mark,

    I thank you for your comments and observations with regards to the Dieselguard. It would be great if certain private individuals were able to conduct themselves in an intelegent manner and engage in a constructive debate with regards to the issues surrounding diesel misfuelling as oposed to employing their substandard computer skills in an effort to obtain better google ranking using blog pages. The offending persons should either be birched or tied to a ducking stool.
    Better enjoyment would be gained from these pages and other blog sites without these people spoiling it for others. I think it is a real shame that a person should deliberately ‘diss’ something or someone for financial gain using a free service such as blogs, do they not recognise the fact that their malicious handy work is so transparent and obvious to those who possess the very basic IT skills par intelegence with optional Auto Pilot, obviously somebodys Auto Pilot requires a degree of re-programming to prevent it from malfunctioning in the future. Probably the best football team in the world, Liverpool. Yes, Liverpool, a city north of London, Magnetic North, grid north, true north

    I once bothered to write a letter to Goverment expressing my concerns about Diesel misfuelling, believe it or not I actually received a reply, not from Tony Blair but from his secretay expressing the fact that deat Tony would like to have replied to my letter but was most busy and saying thank you for the sample and how I should contact the department of trade. To be honest I was rivetted to receive a reply at all never mind being told that the Tony had actually bothered to look the sample over! However, I was dissapointed that despite my attempts to raise the issue of diesel misfuelling at the highest level it was brushed under the carpet.

    At present I beleive there are around 550 misfuelling incidents per day, the actual number being a lot higher when one takes in to account that most incidents go un reported by those worried about it having an adverse effect on their vehicles mamafacturers warranty.

    Diesel misfuelling is a serious issue that is being largely ignored by both Goverment and industry.

    The last figures I had indicated that incidents of diesel misfuelling was costing the British motorist in excess of 120 million pounds in repair bills alone.

    Putting the wrong fuel in your vehicle is big business for the petrol companies. I do not have any relieble data as to the volume as to the hundreds of thousands of gallons of cross contaminetd fuel that is wasted, but I do believe that in America one has to pay a penalty charge fee for having to dispose of ‘hazardous’ material.

    What happens to or how the cross contaminated fuel is disposed of in this country I do not know, but its out there somewhere. I would be most interested to hear what happens to or how it is disposed of.

    Recently there has been a lot said about the modern diesel engine and how simply pressing the unlock button on your key fob can result in permanent engine damage if you have misfuelled your diesel vehicle. Does anyone have factual proof that this is true or is it simply scare moungering? Who knows….

  12. I’m not sure who the private individuals that Kirk refers to are but I assume it’s not yours truly as:

    • If my computer skills were substandard, I wouldn’t have a successful IT career (where I currently work for one of the world’s largest IT service providers and my opinions have been quoted in the IT press on multiple occasions) and this (largely IT-related) website wouldn’t attract sufficient visitors for the resulting revenue to fund the odd gadget purchase.
    • The PageRank on this blog is presently much higher than that of either Diesel Guard or MagneCap and the link from the main post is actually benefiting Diesel Guard’s PageRank (links in the comments won’t help though); however there is little benefit to me from this page, which, at the time of writing, has a very low PageRank (2).
    • Even though I have a very reasonable agreement with my hosting provider and I use open source blog software, this site is anything but free – especially when considering that I invest a lot of time and effort in researching, writing and maintaining the IT-related content on this blog and wouldn’t do it if people didn’t find the advice that is given here useful (the majority of the comments left on this blog are either constructive additions to my work or thank you notes when the advice helps someone out). This particular post is unusual in that it’s not got anything to do with IT, indeed the technology link is pretty tenuous.
    • I travel extensively within the UK (and occasionally further afield) and am perfectly aware where Liverpool is (a short ferry-ride across the river from the Wirral, where Diesel Guard is based); although I fail to see the relevance in the context of this discussion (BTW, the football team that I follow play in sky blue, can be found in nearby Manchester, and will be playing hosts to Liverpool FC this weekend – although, to be honest, I prefer the game with the oval ball).

    I have no doubt that misfuelling is a big problem – I even linked to the AA Motoring Trust’s 2004 report in my original post and I’m sure that’s why the owners of the car that I drive sent me the Diesel Guard to fit; however my comments still stand. I believe I’m still entitled to express my views in this country (despite the efforts of the current administration who simply pay lip service to the views of motorists over much more significant issues than misfuelling) and if my blog is where I choose to rant then that is my prerogative. Based on the 550 misfuelling incidents a day that Kirk quotes, and assuming £50 for each full tank (some will be more, many will be less), then that’s only £10m – not exactly big business for the petrol retailers but clearly worth a lot to vehicle repairers (Kirk cites £120m). If people want to spend £12.50 on a Diesel Guard, or any other product to help avoid misfuelling, then that’s entirely up to them – I simply object to LeasePlan’s attempts to get me to fit this device (which stopped working within a year) in an attempt to hold me responsible for any future misfuelling. To answer Kirk’s question about contaminated fuel, I believe that in this country it is sold to innocent consumers by the supermarkets ;-) (for those without a sense of irony, that was an entirely facetious, and rhetorical, comment relating to another recent news item).

    I detect a sense of bitterness in Kirk’s responses to this blog post – maybe that’s because Kirk has the task of marketing this product and, according to Companies House, Dieselguard Limited (the registered company name quoted on the Diesel Guard website – registered number 05033951) was dissolved on 9 January 2007 (I assume that Diesel Guard is still being sold, as a new company called Dieselguard UK Limited – registered number 05820400 was incorporated on 17 May 2006 and is still active).

    Right, I’ve wasted enough time today on this old, low ranking, page – I’ll get back to researching/writing something more useful (and probably IT-related).

  13. This product wasn’t made for you or Brits with 4cyl. VW TDI’s. It was made for lowly uninteligent Mexican-American constuctions workers that found themselves driving the bosses Power-Stroke.
    On the other hand, It seems like Dieselguard has found more idiots in Europe. Maybe your government should consider making it physically difficult to missfuel by changing your nozzle design standards… or have Kira Nightly on the device, telling you not to be a moron and reach for the green nozzle.

  14. @Bob – If it’s not for us Brits with 4 cylinder TDIs, then why’s it sold here (someone certainly sold it to the leasing company that owns my car…)? Also, perhaps you should learn to spell before criticising others’ intelligence (leaving aside the fact that your argument seems to be based purely on their ethnic background)? Finally, much as I like the idea of Keira Knightley’s involvement in my frequent visits to filling stations, the whole point is not to reach for the green nozzle…

  15. A new device to prevent motorists putting the wrong kind of fuel in their cars has also been developed at Wolverhampton University.

    The inventor, Martin White a retired Royal Navy Commander, partnered with the Caparo Innovation Centre at Wolverhampton University to develop and license the patent rights for the new device.

    The diesel misfuelling prevention device is a retrofit product, which is installed as a direct replacement for the vehicle’s existing fuel filler cap. In its normal state, the mechanical device forms a physical barrier across the fuel intake aperture preventing access to the fuel tank.

    The device is configured so that when a diesel fuel filler nozzle is inserted the physical barrier swings out of the way allowing fuel to be added to the vehicle. The device can distinguish between petrol and diesel fuelling nozzles and will not open when it is attempted to insert the smaller diameter petrol nozzle, therefore preventing the wrong fuel being added to the vehicle.

    The product is being taken to market by Caparo Vehicle Products, who have improved the design to make it suitable for volume production and are currently producing and testing advanced prototypes.

  16. Hi,

    My company DDN Ltd has just brought to market our MPD (Misfuel Prevention Device) Once installed the MPD completely eliminates the accidental misfueling of a diesel engined vehicle with petrol. We have a wide range of solutions for passenger cars, car derived vans and light commercial vehicles. Please take a look at our website: for further information.

  17. I’m not sure what it is about this old blog post that’s such a magnet for comment spam from small businesses competing to stop us misfuelling our cars but the latest device to be mentioned here looks remarkably similar to the fuel filler cap on the Ford Mondeo I’ve been driving this week.

    Surely, rather than buying aftermarket devices, we should really be putting pressure on manufacturers to help solve this issue (but they have a vested interest in misfuelling because it’s their franchised dealers who we pay the hefty repair bills to). So, it looks like Ford are on board – anybody else?

  18. Hello Mark and all,

    Firstly thank you for such an informative site and in particular this subject. I am one of the many who has just experienced misfuelling saying in the past of course, ‘it will never happy to me’. Using a forecourt assist and 380.00 later I can say I have taken a deep interest. I do agree that the makers should be dealing with this problem at source but as already stated thiere to too much money to be made with this problem. I don’t want to seem to support one particular product but I do mention the Solo Diesel product purely because that what I can talk about with personal experience. Its a solid unit and I really hope that it saves me any further mess.. there are lots of units on sale so be-sure to do your research :)

    Best, Dan

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.