We've had a number of threads mentioning additives generally and I've joined in with my Ha'penny worth myself. So people will know that I'm not a fan of additives. In particular I don't "do" oil additives, I think the money is much better spent on a quality oil. I'm not that fussy about the brand - although I do go for names I "know" and trust - and I don't do extended change intervals. ("Family Fleet" vehicles are done every 12 months or 10,000 miles whichever comes first) and always a filter change at the same time. I'm not a fan of flushing but I'll say no more on that as is can get complicated.
Fuel additives are a bit more complicated. As Jim was saying above, there are fuel additives which you add a whole can at a time - so high concentration - which are intended to clean the system and especially the injector spray holes. These work well if the injector is not grossly contaminated but will probably need more than one dosing if the nozzle is quite dirty. However a seriously clogged nozzle is probably going to need a proper ultrasonic clean up. Probably running a premium fuel which will have higher concentrations of these beneficial ingredients incorporated in them is a better long term solution though. I owned my old 1.9tdi SEAT Cordoba for 19 years and clocked up well into the low 100,000s of miles with it. That was when Low Sulphur diesel was first introduced and there were problems being reported of excessive wear in high pressure injection pumps and injectors due to the low lubricity of these new fuels. I got very worried about the "old style" distributor type pump and traditional spring type injectors in this car which were designed for use with the older fuels so I went looking for an additive which specifically improved lubrication. I came up with Wynns Eco Diesel. (The Wynns brand I knew well from my Drag racing days)
https://www.wynns.eu/product/eco-diesel/ This is a product which you dose every tankful with so it's always there. I thought I had a small injector problem at around the 90,000 miles so pulled the injectors and handed them in to Lawsons Diesel (trusted local diesel specialist) for a check over. He dismantled and cleaned them before reassembling and setting the blow off pressures - which had dropped a little with the springs aging - He said he really couldn't find anything wrong with them and was astonished they'd done 90,000+ miles He gave me a free set of sealing washers and new blow off pipes and said he was still embarrassed to be charging me the £25 he did. I'm convinced this lack of wear was down to the Eco Diesel. By the way, it always passed it's MOT with a "Fast Pass" so only one revving up to the governor limit each year!
Now I have the Ibiza with its tiny 999cc 3 cylinder direct injection turbocharged petrol engine. There are a number of things which concern me about small direct injection petrol engines Injector clogging due to the tip being in the combustion chamber is one and inlet tract carbon fouling is another. There are also issues of high pressure pump wear reported, especially on the earlier systems. So I set out to find an additive which would perhaps help with these issues and came up with Archoil AR6900-P Max :
https://www.powerenhancer.co.uk/arc...d-petrol-synthesis.html#tab-label-description Again this is a product which you add a small concentration to every tankful so it's always there so always working. I'm not at all convinced about whether it can do much for the inlet tract fouling being as how it's being introduced directly into the combustion chamber? but we'll see. Unless she starts playing up before then, I'm planning to take the inlet manifold off (a bit of a job as it has an integral water cooled intercooler) at around the 50,000 mile mark and have a look into the ports. I'll do a post about it when the time comes.
At present I'm running the Ibiza on Morrison's 95 octane juice which is the fuel octane recommended on the filler cap. I have been meaning to try her on a few tanks full of the Shell premium fuel (which everyone seems to say is the best currently available) to see if fuel economy or performance is noticably increased. Being turboed this engine is bristling with knock detectors etc so should be able to take any advantage available from the higher octane fuel and use it to best effect. I also feel concerned about LSPI which can be a problem with these wee turboed engines - although it doesn't seem to be a particular problem with the VAG units - A higher octane fuel should make pre ignition less likely too. Also of concern was the piston problem on the earlier TSI's where they would break up the piston ring lands. I understand that was a materials problem with the metal the pistons were made from and has been addressed on later units - fingers crossed!
In conclusion then I'm still not a fan of additives for lubricants but do see a place for fuel additives to address specific circumstances. Generally though I think you could spend quite a lot of money on additives and gain very liitle benefit.
