Fuelling my GT

[GolfTi]

Oh err!! don't know how i posted twice, and no i've not been drinking.

You sure ?  ,i think gizzy you should stick to the 95 ron,you will save yourself money as you don`t seem the type to thrash the living day lights out of your car,with the gti its probably a placebo effect when using higher ron,there were some good videos on you tube done by fifth gear i think ?,it only really made a difference on the really high powered cars.

Not sure about the money saving bit. 98/99 will give you better mpg.

As I said earlier I am totally convinced the mk 6 GTI runs better on higher octane fuel.

It would be really good to get some rolling road results for the different octanes to show the doubters.

[kartracer]

It would be really good to get some rolling road results for the different octanes to show the doubters.

Here you go:
http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results.shtml

[gizzywizzy]

It would be really good to get some rolling road results for the different octanes to show the doubters.

Here you go:
http://www.thorneymotorsport.co.uk/tuning/Fuel_Test_Results.shtml

Interesting, my GTI friend was right the.  I shall have to go eat humble pie.

[Exonian]

Those tests are done on a dyno, and not on a mk6 GTI - therefore I maintain that VW are correct and it's perfectly okay to run 95RON in normal driving. 

Personally I do use the expensive stuff though as I'm running a 98RON map. 

[ub7rm]

Those tests are done on a dyno, and not on a mk6 GTI - therefore I maintain that VW are correct and it's perfectly okay to run 95RON in normal driving.  :lipsrsealed:

Personally I do use the expensive stuff though as I'm running a 98RON map. 

Of course it is, thats not in question, its perfectly OK to run the mk5 GTI on 95 but you won't realise the engines full potential.  With the mk6, the stated performace / economy figures are based on 95 ron fuel.  Due to the way Fuel Stratified Injection works, the higher the ron rating, the better the economy and performace will be.  This isn't necesserily true for 'old school' injection systems but it is for petrol direct injection.

Whether the cost of the higher ron cancells out any ecomomy gains is another matter.

Coming from a mk5 perspective:  There is a big difference in performace when I've run on 95 - not particularly noticable at lower 'town' rpm's but very very noticable at the higher end of the rev range.  The difference in fuel economy though was slight.

[mac7]

Those tests are done on a dyno, and not on a mk6 GTI - therefore I maintain that VW are correct and it's perfectly okay to run 95RON in normal driving.  :lipsrsealed:

Personally I do use the expensive stuff though as I'm running a 98RON map. 

Of course it is, thats not in question, its perfectly OK to run the mk5 GTI on 95 but you won't realise the engines full potential.  With the mk6, the stated performace / economy figures are based on 95 ron fuel.  Due to the way Fuel Stratified Injection works, the higher the ron rating, the better the economy and performace will be.  This isn't necesserily true for 'old school' injection systems but it is for petrol direct injection.

Whether the cost of the higher ron cancells out any ecomomy gains is another matter.

Coming from a mk5 perspective:  There is a big difference in performace when I've run on 95 - not particularly noticable at lower 'town' rpm's but very very noticable at the higher end of the rev range.  The difference in fuel economy though was slight.

The old school injection on my Mk2 GTI was happier on 98 RON too, both in performance and economy.

I guess the Mk5 has to retard it's ignition timing when using 95 RON, hence the more noticeable drop in performance? Similarly, as the Mk6 is built to use the lower octane, it benefits more from remapping to run on 98 RON.

[ub7rm]

Those tests are done on a dyno, and not on a mk6 GTI - therefore I maintain that VW are correct and it's perfectly okay to run 95RON in normal driving.  :lipsrsealed:

Personally I do use the expensive stuff though as I'm running a 98RON map. 

Of course it is, thats not in question, its perfectly OK to run the mk5 GTI on 95 but you won't realise the engines full potential.  With the mk6, the stated performace / economy figures are based on 95 ron fuel.  Due to the way Fuel Stratified Injection works, the higher the ron rating, the better the economy and performace will be.  This isn't necesserily true for 'old school' injection systems but it is for petrol direct injection.

Whether the cost of the higher ron cancells out any ecomomy gains is another matter.

Coming from a mk5 perspective:  There is a big difference in performace when I've run on 95 - not particularly noticable at lower 'town' rpm's but very very noticable at the higher end of the rev range.  The difference in fuel economy though was slight.

The old school injection on my Mk2 GTI was happier on 98 RON too, both in performance and economy.

I guess the Mk5 has to retard it's ignition timing when using 95 RON, hence the more noticeable drop in performance? Similarly, as the Mk6 is built to use the lower octane, it benefits more from remapping to run on 98 RON.

Indeed - I believe it does.  There was a link to a very good explanation of what FSI was all about and why it made such a difference using high octane fuel but I cant find it at the moment.  Whenever I tried 98 with my mk4 1.8T I could never really notice a difference - if anything it felt a little better on 95.  But the change with the mk5 is very noticable.

Edit:  found the explanation

Regards FSI owners mainly.

The higher the octane rating of the fuel the longer the FSI engine will run in FSI mode.

You see, when the FSI is running in 'Fuel Stratified Injection' mode it creates a lot of NoX (NoX - Very bad as far as emisions go) due to it being such a lean burn, so it has a NoX Cat which abrorbs the NoX, once its full the Nox probe (fancy lambda probe) senses this and the engine switches back to normal running and can safely clear the NoX out with the other gases through the main Cat so it can switch back into in FSI mode again.

The problem with octane levels is, and this is just an example depending on driving styles.

Out of 100 miles average :-

95RON - 90 miles normal, 10 miles FSI (lots of NoX made in FSI mode)

97+RON - 60 miles normal, 40 miles FSI (some NoX made in FSI mode)

Now regardless of what anyone says this is how the engine is built and as its more efficient in FSI mode VW always recommend the highest octane rating for this reason, they did introduce a 1.4FSI for the uk market that is made to run on 95RON fuel for longer but you want to see the size of the NoX Cat, more like a tanker. lol

And after all that, you will get better miles to the gallon running 97+RON regardless of it being an FSI, its they way they are made these days, the ecu recognises when the fuel mixture combusts and will adjust it accordingly, the cheaper the fuel the more retarded the timing, the more retarded the timing the less power, the less power the more you 'need' to put the foot down.

The above was written when the mk5 was released but is still relevant.

[mac7]

Edit:  found the explanation

Regards FSI owners mainly.

The higher the octane rating of the fuel the longer the FSI engine will run in FSI mode.

You see, when the FSI is running in 'Fuel Stratified Injection' mode it creates a lot of NoX (NoX - Very bad as far as emisions go) due to it being such a lean burn, so it has a NoX Cat which abrorbs the NoX, once its full the Nox probe (fancy lambda probe) senses this and the engine switches back to normal running and can safely clear the NoX out with the other gases through the main Cat so it can switch back into in FSI mode again.

The problem with octane levels is, and this is just an example depending on driving styles.

Out of 100 miles average :-

95RON - 90 miles normal, 10 miles FSI (lots of NoX made in FSI mode)

97+RON - 60 miles normal, 40 miles FSI (some NoX made in FSI mode)

Now regardless of what anyone says this is how the engine is built and as its more efficient in FSI mode VW always recommend the highest octane rating for this reason, they did introduce a 1.4FSI for the uk market that is made to run on 95RON fuel for longer but you want to see the size of the NoX Cat, more like a tanker. lol

And after all that, you will get better miles to the gallon running 97+RON regardless of it being an FSI, its they way they are made these days, the ecu recognises when the fuel mixture combusts and will adjust it accordingly, the cheaper the fuel the more retarded the timing, the more retarded the timing the less power, the less power the more you 'need' to put the foot down.

So in the Mk5, NOx emissions mean that the injectors can't run in stratified (lean) mode as often when using 95 RON fuel and this is why fuel consumption increases. The lean burning means the ignition has to retard with 95 RON (to prevent detonation) and that is why power is reduced.

On the Mk6 presumably using 97-99 RON would have the same effects (increased power/economy), so 210bhp is just the starting point 

[ub7rm]

So in the Mk5, NOx emissions mean that the injectors can't run in stratified (lean) mode as often when using 95 RON fuel and this is why fuel consumption increases. The lean burning means the ignition has to retard with 95 RON (to prevent detonation) and that is why power is reduced.

On the Mk6 presumably using 97-99 RON would have the same effects (increased power/economy), so 210bhp is just the starting point 

Thats my view on it aswell. 

[simonpolly]

If using 98 ron was beneficial Vw would recommend you use it,if its more economical and you get higher performance then why don`t they tell you to use it?,its only more economical if the extra miles per gallon you get out weighs the price difference.The fact they say use 95 says it all.