Petrol additives harmful to injectors?

Elessar

I've read recently that additives in the petrol of certain fuel companies can be harmful to injectors and cause carbon buildup which clogs them. Is this true?

Also read that additives can actually decrease MPG instead of increase it as the likes of Topaz advertise. True/false? What additives are they actually using?

Does anyone know which, if any, companies sell 100% petrol, or petrol with the lowest amount of additives?

As the owner of a new 1.2TSI I would like to make sure I use the purest fuel all the time. Personally speaking, I noticed that fuel from Esso has given me some of the best MPG.

Matt Simis

Why would they add additives that actually harm their market?! Seriously.
The additives are things to improve cleaning of injectors, remove water etc. Using your example, Topaz use Techron, which is sold in pure concentrations in the US in a can and is a well regarded fuel system cleaner.

Unless you are talking about Ethanol (5-10% these days in all petrol), which most definitely isnt an additive, its a fuel in its own right. It can be harmful to ancient fuel systems (pre 1980) or harbor water (its hygroscopic) but at such low concentrations, dont worry about it.

The issue with the FSI and TSI engines is one of design, the Stratified injection system is prone to coking up and is well documented online. Fuel isnt the problem.

I've seen reports of FSI engines getting a carbon build up on the tops of the valves, mainly due to the crankcase breather - oil vapours are recycled into the top of the block to be burnt off in the cylinders. In a non-FSI engine, the valve tops are washed with petrol and only accumulate a hydrocarbon build up slowly. in an FSI engine of course, there's nothing to wash the valve tops, so this becomes a potential problem.

http://www.audizine.com/forum/showthread.php/334489-RS4-Intake-Manifold-Carbon-Build-Up-amp-Clean-Up
http://www.radardetector.net/forums/car-talk/72199-audi-fsi-engine-carbon-update.html
http://www.tyresmoke.net/forum/audi-technical/125318-fsi-carbon-buildup-k-audi-black-lung.html



http://www.carworklog.com/2011/09/10/common-issues-tips-and-tricks-for-the-2-0t-fsi-bpy-engine/

Engine valve buildup:
Because of the way the 2.0t FSI’s fuel injection works the gunk can buildup overtime on the valves by oil and junk flowing through the PCV system to the valves. to the left is a picture of what valves can look like overtime.
Loss in performance is a sign that this might be happening. But that is also a very vague sign that could be the result of a lot of things.

If you already have buildup the best way to resolve it is take it apart and clean it. This is a very time-consuming task or expensive if you have a shop do it. You could try using a cleaning solution like Seafoam or BG Induction Cleaning that don’t require taking everything apart.

To prevent buildup it is a good idea to install a catch can. This will catch the foreign contaminates in the PCV system before they get to the valves. You will need to empty the catch can every so often. A good time is when you do your oil changes.

Ironically you're looking to blame additives and its infact an additive thats recommended to combat the problem. Good luck on that one.