Good Evening Doctor. I would be interested in your comments concerning the use of certain combustion improving diesel fuel additives in modern vehicles and, specifically, whether or not you think that they are worth the money. I remember Diesel Car magazine performing a test on a Ferrous Picrate product called Unicat 4 many years ago and finding out that it worked quite well, and was value for money. This product is no longer available in the UK, but there is another, similar, product available called FPC 1 to be found at: www.fueliq.co.uk/fpc/. Alternatively, there is another fuel additive called Dipetane – which has been sold for many years and is offered premixed with bulk heating oil from some suppliers: www.dipetane.com. Each of these products seem to have well proven benefits – but then they would say that, wouldn’t they! I know that modern diesel engines are very efficient, with apparently little room left to improve things further with additives. Personally, I just use a double dose of Millers Diesel Fuel additive to boost the cetane index of supermarket diesel in my 2008 Mercedes-Benz GL 420 CDI SUV, and lubricate the high pressure pump/injectors, as well as removing/preventing injector deposits.

If you remember, I asked you some time ago if you would be visiting the Ceramex company www.ceramex.com to see first-hand their diesel particulate filter (DPF) cleaning process, as this would potentially be of interest to your readers. I am just wondering if this is still on your “to-do” list?

On the subject of DPF ash blockage, I wonder what influence the up to seven per cent bio-diesel now added to diesel fuel has? I used to work in a factory which made bio-diesel from used vegetable cooking oils and well remember the necessity to ensure that as little process chemicals remained in the finished fuel as possible. The most commonly used (cheapest) process chemical used to make bio-diesel is sodium hydroxide (plus methanol) which, if not entirely removed through washing/filtration, can cause injector blockage and presumably also problematic DPF blockages?

Can you also ask the editor, please, if he intends arranging for test reports of the BMW Alpina versions of the current 3 & 5 series cars? Regards,
Danny Gillis

Hello Danny. I hope that the Mercedes is continuing to run well and problem-free. I well remember the Unicat 4 additive which, as you say, disappeared from the market. There were also favourable and superficially convincing reports on the web regarding ferrous picrate, and I’m not sure why it has disappeared from use or sale – at least in the UK, anyway. I was not aware of Dipetane or FPC 1, and I have to suggest that the regular disappearance of companies offering such additives makes one somewhat suspicious. But I can guarantee you some column inches if you want to be brave enough to experiment and let me have any interesting reports. With regards to ferrous picrate, there is some suggestion that this stuff actually aids atomisation of the fuel on injection, That’s interesting, as the higher and higher injection pressures being used are obviously also directed at better atomisation. There was a US company, a few years back, who offered an additive specifically aimed at improving atomisation, and I did try and get hold of some, but the business apparently expired, as I heard no more from them.

Regarding Ceramex, and DPF regeneration, I feel that, and could suggest, that most Diesel Car readers have no cause for DPF regeneration, as they drive and maintain their cars sensibly. But we would welcome any feedback from readers who have used such restoration services. As you say, bio-diesel ash can present problems, particularly that from questionable sources of such fuel. As I now understand it, the legally required bio-diesel content under the “Renewable Fuels Obligation” regulations was actually frozen at 4.75 per cent back in 2013, possibly for reasons connected with problems at higher levels. I do believe that the UK is still a net importer of bio-diesel, which also may have had some effect, but the original target level of seven per cent has not been reached.
I think Ian has tried before to get an Alpina on test, and I think he found it a problem to get a test car. But he will see this correspondence and it may spur him into another attempt. (We have tried on several occasions, but the PR effort for Alpine is lethargic at best, so with many other vehicles to test, we gave it up as a bad job! Ed)

Meanwhile, I will take a closer look at the Dipetane fuel additive. Regards,
Doc