Andyuk911 Posted November 20, 2007 Report Share Posted November 20, 2007 I often hear people ask this question. There are several reasons, not only to run 97-99 octane to gain power by the ECU advancing the ignition, but also for the EXTRA cleaning additives these petrols have. This is a demo by BP at a Silverstone BTCC event in 2006 You can see the probes on the modified engine This is from the '97' octane side, note how clean it is. Look how bad this side is .. the normal '95' side .. just shows how poor the petrol is The TWO tanks in the boot, one running each bank So next time you fill up, that is what you are paying for. Link to comment Share on other sites More sharing options...
Golfer Posted November 20, 2007 Report Share Posted November 20, 2007 Very good info Andy.............. must get to the pumps............... the 99oct ones anyway. Link to comment Share on other sites More sharing options...
PetrolDave Posted November 20, 2007 Report Share Posted November 20, 2007 The other advantage of 97/99 petrol is that it costs less to run your RS4! How come? 97/99 petrol has a lower sulphur content than 95 petrol - because of differences in the refining process. The FSI engine, like the RS4, has a cat that absorbs the sulphur content, but when that cat becomes "full" the engine fuelling and spark timing is changed to increase the exhaust temperature and hence inmcrease the temperature of the cat and burn off the absorbed sulphur. Result? - increased fuel consumption, by about 10%. So provided 97/99 petrol doesn't cost more than 10% more than 95 petrol, not only do you get more power and a cleaner engine but it also costs you less to run. Currently where I live 95 petrol is 98.9p per litre and 99 is 103.9p per litre - so using 99 decreases my fuel costs by about 5%. Link to comment Share on other sites More sharing options...
Mook Posted November 20, 2007 Report Share Posted November 20, 2007 [ QUOTE ] The FSI engine, like the RS4, has a cat that absorbs the sulphur content, but when that cat becomes "full" the engine fuelling and spark timing is changed to increase the exhaust temperature and hence inmcrease the temperature of the cat and burn off the absorbed sulphur. [/ QUOTE ] Bloody hell - I didn't know that Does this only apply to the FSI engines? Link to comment Share on other sites More sharing options...
kite Posted November 20, 2007 Report Share Posted November 20, 2007 [ QUOTE ] [ QUOTE ] The FSI engine, like the RS4, has a cat that absorbs the sulphur content, but when that cat becomes "full" the engine fuelling and spark timing is changed to increase the exhaust temperature and hence inmcrease the temperature of the cat and burn off the absorbed sulphur. [/ QUOTE ] Bloody hell - I didn't know that Does this only apply to the FSI engines? [/ QUOTE ] Some diesels clean their cats this way Link to comment Share on other sites More sharing options...
Woppum Posted November 20, 2007 Report Share Posted November 20, 2007 I wouldnt dream of filling up with anything diffrent even for the placebo effect. well and becasue my taxible fuel benifit would be no difrent! Link to comment Share on other sites More sharing options...
PetrolDave Posted November 21, 2007 Report Share Posted November 21, 2007 [quoteDoes this only apply to the FSI engines? [/ QUOTE ] Petrol - only the FSI engines. Diesel - as kite has said some do it. But I'm not sure if it's only ones like the Peugeot HDI FAP ones? Link to comment Share on other sites More sharing options...
kite Posted November 21, 2007 Report Share Posted November 21, 2007 The 170 VAG diesel has DPF Link to comment Share on other sites More sharing options...
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