[neild41]

I have the new(ish) TSI engine, the 1.4 to be precise but don't think that matters for this question - does anyone think its worth using Super unleaded ( the higher octane version for our overseas people ) either all the time or once in a while ?

Neil

 

[silvershadow]

I have the new(ish) TSI engine, the 1.4 to be precise but don't think that matters for this question - does anyone think its worth using Super unleaded ( the higher octane version for our overseas people ) either all the time or once in a while ?

Neil

The general consensus around the world seems to be that using the highest octane fuel available will improve performance and possibly fuel economy depending on how the car is driven. The engine mangement system automatically adjusts the fuel injection cycle and ignition timing to optimise the engine performance relative to the fuel. The main decision for the owner is whether the better performance and possible increase in fuel economy compensates for the higher price of the fuel.

One point to keep in mind is that it does take time for the engine management system to find the optimum settings for a different fuel so initial impressionms after filling the tank MUST be ignored as the engine will be running under settings for the previous fuel. It is not unusual for the initial performance and fuel consumption to be worse than previously until the system adjusts itself. I would suggest you wait until you have used several tanks of fuel before making comparisons.

 

[neild41]

cheers for that in depth response - I have always ignored the possibility here because of the cost difference but going to France in a couple of months and I notice the difference is quite small and then that got me thinking about the benefit of either etc etc

 

[Blessed_Badger]

The general consensus around the world seems to be that using the highest octane fuel available will improve performance and possibly fuel economy depending on how the car is driven. The engine mangement system automatically adjusts the fuel injection cycle and ignition timing to optimise the engine performance relative to the fuel. The main decision for the owner is whether the better performance and possible increase in fuel economy compensates for the higher price of the fuel.

One point to keep in mind is that it does take time for the engine management system to find the optimum settings for a different fuel so initial impressionms after filling the tank MUST be ignored as the engine will be running under settings for the previous fuel. It is not unusual for the initial performance and fuel consumption to be worse than previously until the system adjusts itself. I would suggest you wait until you have used several tanks of fuel before making comparisons.

Totally agree! I have the 2.0T and started off using the regular 95ron. Was getting about 28 mpg . Changed to Tesco 99ron and am now getting nearer 32mpg therefore making the increase in price pay for itself with the better mpg. I tried Shell V-Power but there are no garages close by (same with BP (Ultimate)) so the best I can get on a regular basis is the Tesco's stuff!!

It takes a good few tank fulls before it takes effect as said above. Would recommend running tank low before filling up to stop the 2 types of fuel mixing and diluting together. All the recent VW engines 'sense' the type of fuel they are getting, and once they are sure what it is they alter the timing to reflect this.

To be honest, I haven't noticed any significant change in the performance but I have heard that further down the line the better fuel means you're less likely to have engine problems - so while it's not really costing anything I'll probably carry on with the 99' from Tescos.

 

[neh321]

Don't agree!
The general consensus in the motoring world has always been that if you use a lower octane fuel than the engine is designed for it will adversely affect performance (i.e. if you need 95 RON then you must use at least 95 RON) but if you use a higher octane than the manufacturer tells you to use it makes not one single iota of a difference to the engine's performance.

Of course the petrol companies' advertisements will try to convince you otherwise but it will not increase your performance or your fuel economy but will damage your wallet.

My 2.0T needs 97 RON according to the fuel flap so I always put 98 RON in (because you don't seem to be able to get 97 in the UK) but according to the handbook then if 97 is unavailable then 95 is OK and will only reduce your engine's output by a couple of bhp, as long as you put 97 in sometime in the next few fill-ups.

 

[neh321]

Of course my above post assumes that the 1.4T doesn't actually ask for 97 RON; if it does then that's what must be used (at least for most of the time).

 

[Blessed_Badger]

My MKV Golf GTI had the same engine as my Eos. As with the Eos, the performance was the same when using different ratings / RONs of petrol but in both cases the mpg I was getting went up by 10-12%, and therefore more than made up for the extra cost (about 5-7%) in the petrol.

The Golf GTI recommended 97RON, but for the first 6 months I used 95 with no adverse effects (after reading on Tyresmoke / Golf GTI Forum that it was fine to use this). I only changed because the Tesco near us started doing the 99RON petrol and I wanted to see if the performance would increase (which it didn't!). Although, as I said, the fuel economy did!

From my own experience therefore I have had an increase in economy but not in performance.

 

[Lucid Nonsense]

Cost aside, it sounds like you all have no problem finding higher octane gasoline - I wish that were the case over here! Sometimes the highest rating I can find is 91 [(R+M)/2, equivalent to 95 RON]. That's fine for our 2.0T TSI Eos because that's what's recommended on the fuel filler door and the manual. However, I'll be getting an APR tune this summer, and I'd really like to get the 93 octane version (~98RON). Have to be sure I have enough local stations carrying that rating, because I don't want to have to drive across town to fill up.

 

[silvershadow]

Don't agree!
The general consensus in the motoring world has always been that if you use a lower octane fuel than the engine is designed for it will adversely affect performance (i.e. if you need 95 RON then you must use at least 95 RON) but if you use a higher octane than the manufacturer tells you to use it makes not one single iota of a difference to the engine's performance.

Of course the petrol companies' advertisements will try to convince you otherwise but it will not increase your performance or your fuel economy but will damage your wallet.

My 2.0T needs 97 RON according to the fuel flap so I always put 98 RON in (because you don't seem to be able to get 97 in the UK) but according to the handbook then if 97 is unavailable then 95 is OK and will only reduce your engine's output by a couple of bhp, as long as you put 97 in sometime in the next few fill-ups.

Without being too technical here - you are confusing octane rating with energy content for the fuel concerned.

The fuel components blended together to achieve the desired octane rating have varying energy [calorific for the technically minded] values. The engine management system does not respond to the octane rating of the fuel but it certainly responds to the energy content of the fuel by adjusting the combustion conditions to "optimum" [as determined by the manufacturer for the engine concerned]. This is achieved by varying the quantity and timing of the fuel injected into each cylinder and by varying the spark timing. The engine is fitted with sensors that determine if pre-ignition [pinging or knocking] is occuring as well as monitoring the exhaust gas oxygen content as these provide the necessary indications that the management settings in use have exceeded the capability of the fuel to combust efficiently. This why an engine with modern engine management systems can use both higher and lower octane fuels as alternatives to the specified fuel without damage but the power output will vary depending on the octane rating. The fuel economy achieved in both situations then depends on the manner in which the car is driven.

Higher octane fuels always use additives with high energy content so this is the reason why they give lower fuel consumption/higher mpg[l/100Km] figures than those achieved with the specified minimum octane rating for the engine PROVIDED THAT the car is driven in the same way for each fuel. Accelerating harder and changing gear at higher revs than usual as a consequence of the extra performance achieved with higher octane fuel will certainly increase fuel usage to the detriment of fuel economy.

I trust this will be of assistance.

 

[cb391]

LN, what brands do you have in Va? Here we have Shell, BP, Citgo, Marathon, and a few others. The four I mentioned are all selling 93 octane premium albeit up to 10% ethanol. But we have air pollution standards here that may be different than yours which may mean a difference in fuel requirements.

 

[silvershadow]

LN, what brands do you have in Va? Here we have Shell, BP, Citgo, Marathon, and a few others. The four I mentioned are all selling 93 octane premium albeit up to 10% ethanol. But we have air pollution standards here that may be different than yours which may mean a difference in fuel requirements.

This should not be a problem for US-delivered vehicles as it is standard practice for the engine management system to be calibrated during assembly by the manufacturer for the fuel and vehicle emission standards applying in the country of destination [even for individual States which used to be the situation when California had different standards to the rest of the USA in the 1980's - this may still be the case].

 

[Lucid Nonsense]

LN, what brands do you have in Va? Here we have Shell, BP, Citgo, Marathon, and a few others. The four I mentioned are all selling 93 octane premium albeit up to 10% ethanol. But we have air pollution standards here that may be different than yours which may mean a difference in fuel requirements.

We've got the usual - Shell, Exxon, Citgo, etc. I know I've recently seen 91 instead of 93 at some stations, but I need to note which ones and where to save myself the trouble of pulling in and being disappointed. If I do decide to get the APR 93 tune for the Eos, it really shouldn't be too much of hassle finding the higher octane gas. It's more of a problem finding the $600 to get the upgrade done.

I really need to go by Costco more often - today they had 93 at $2.48/gallon. Quite a savings over the gas stations. I was bummed I was driving the CRX (which needs premium due to mods) and could only fit 4 gallons in the tank!

 

[SiJ2000]

ESSO Super Unleaded seems to work the best in the 2.0 Turbo FSI...