Why use Super unleaded petrol?

[Andyuk911]

This topic keeps popping up in relation to the RS4

Because the engine is an FSI, it can make carbon in the intake ..

So I thought I would post here ...

I have mainly used Shell V-Power, some Tesco 99 and BP Ultimate

Note. Charlie of Surrey RR said to me that cars on BP Ultimate have been know to make less power .. possibly down to a lack of sales and thus 'old' petrol. SO ALWAYS use a busy petrol station.


Here are some pictures that say a thousand words and explain the benefit of using high quality petrol ... they have more cleaning additives..



The first picture shows the probes into the manifold







Here we see the side that is running on BP Ultimate








Here is the side that is running STANDARD BP petrol






This picture shows the TWO tanks in the boot.






I hope this goes to explaining how looking after your car with good quality petrol will be rewarded.

[Tame Technician]

This demonstration is a nice visual presentation to show people and sell fuel. It clearly shows the cleaning ability of better fuels, on a NORMAL 4.2V8 (Not FSI)

As FSI engines have the injector spraying directly into the chanmber rather than at the back of the valve. So the valve would, eventually with milage, look oily and gummed up regardless of what fuel was used.

However, presuming the fuel had not aged, the increased anti knock adatives in the better fuel (the octane rating 99 vs 95) should give the engine slightly more power. The more ignition advance you can run the more power you will make, to much igntion advance and you get knock, better fuel wont knock so early allowing more ignition agvance and hence more power.

I use shell V power in my motor bike (mostly for protection/cleaning rather than power), but when I had tuned turbo cars, that were always right on the limit of knock all the time I believe I could tell the difference.

[Andyuk911]

I understand what you are saying re the FSI engine, however, it is a fact the intake on the FSI 4.2 V8 carbons up and the only fluid that can get near that is fuel.

[VAG1]

i went to VW for some engine noise and the first thing the tech asked me was "what kind of fuel do you use?", i do use V-Power in my FSI engine, can't tell the difference between normal shell unleaded but i put it in anyway.

[Fort Jefferson]

Andyuk911 said:

I understand what you are saying re the FSI engine, however, it is a fact the intake on the FSI 4.2 V8 carbons up and the only fluid that can get near that is fuel.

The only way fuel can get into the intake manifold on an FSI, is back past the inlet valve before it closes.

[Thirsty33]

Sort of the wrong forum (ie not a VAG car), but related to using superior fuels (V-Power, Tesco99 etc).

The short answer is:-

You get more power, more torque and a quieter engine. The effects of power will be less if your car does not have variable knock control but most, perhaps all, recent cars do.

My recent experience relates to a Vauxhall 2.0 200Turbo enginee 2005 year. On regular unleaded, the car lacked low end pull and was also raucous when pushed, giving a very raspy exhaust note (you might like that, I didn't and it gained me lots of abuse whenever I passed people).

On V-Power or T99 (whichever is closer/cheaper), the low end has arrived, and the engine is a pleasure to drive, always willing and I no longer get the angry flashes and "maxwell house" signs when I overtake people.

What erks me is that if the pictures above are true, then in essence, regaular fuel is not fit for purpose and should not even be sold IMHO. Super unleaded should just mean more oactane and more power, not be the only way to keep your engine clean.

[bertelli_1]

All regular 95RON fuel starts off the same whether its sold on a tesco, BP, esso forecourt. Each company then adds its own additives - detergents etc. Obviously the less additives you add, the more profit you make.

I used to do promotions for BP (including the Audi pictured) and the car in question was 2nd hand when converted, then run for a few thousand miles & actually cleaned up the previously dirty cylinders.

[Andyuk911]

What does BP know about 'FSI' or Direct Injection engines ?

The reason for the question is the fuel is injected directly in the cylinder ... thus the valves become dirty due to oil vapour in the intake.

Running BP Ultimate or any other Super Unleaded petrol does NOT help to 'clean' the engine.