High Octane Fuel

[fauconberg]

I'm new to finding engines interesting so please forgive the question if the answer's obvious....

I was wondering if I should/n't put higher octane fuel in my 1.8T, such as Tesco 99 or V-Power? Will I notice any power difference or is this fuel not suitable for these engines?

Thanks.

 

[aragorn]

The main advantage of higher octane fuel, is that it allows you to run more ignition advance, however you personally cant control the ignition advance, its all down to the engines ECU.

Afaik, standard 1.8T's arent mapped to take advantage of anything above 95 octane, whereas if its chipped (or is a 180hp model) then it will. Thats not to say you wont see any benefits from running super unleaded, however if its a stock 150hp engine then its largely money wasted imo.

 

[Oranoco]

Mine saw no difference at all running Super in it as a standard car. When I chipped it and started to use Super it was great and when my dappy ex threw 95 in as she was a dumbass and "it was cheaper" the car ran notably down on power and felt very lethargic

 

[jcb]

well mine definitely sees an advantage on optimax.
seats of th pants dyno is up!
run it dry and fill up and it is a different car

 

[aragorn]

jcb: the AJL is mapped for it, and the handbook explicitly specifies 98 octane fuel, and says it will be down on power running 95.

AEB is not, and the handbook only mentions 95. Obviously if the AEB is remapped, then it will make a difference.

 

[Matt82]

and a good starting point is to just look in the fuel filler flap. it will show the RON that is required.

my S4 requires 98 (or is it 97) from the factory, you run on reduced power otherwise and in theory reduced efficiency (ive not got round to running the S4 on 95 though so i cant comment on that) but with my golf, that has an aftermarket chip and i do get more mpg on higher RON

 

[aragorn]

Ye S4 is mapped for 98 too, and again it'll run on 95 but with reduced power output.

If you put 98 octane fuel in a car only mapped for 95, you can actually end up with a reduction in MPG, as it burns slower and without the extra ignition advance you get less power from each bang.

Most remaps will specify 98 because it helps control det from the higher boost pressures/cylinder temperatures, that said the FWD was mapped and only ever got 95, but dawn didnt really drive it hard enough to justify the additional expense of 98 imo.

 

[Matt82]

one thing i hate is the psychological dilema in the petrol station. 95ron is 119p/litre in most places, 98ron is 123p-125p a litre. its beyond some sort of psychological barrier and you feel its hard to justify it, but in reality 5p a litre more is only about £2 extra a tank (in the golf) and again not much more extra again in the audi.

 

[fauconberg]

I decided to fill up with some super anyway to see for myself. My tank was half way into reserve and I put 30L of Tesco 99 in. I'm pretty sure its not my imagination but the car seems to be a lot more confident when it comes to town traffic, pulling off in 1st and any labouring. There is a lot less judder and splutter when driving in inappropriate gears!

I don't know about power or MPG yet as I haven't hit the motorway but so far I think there has definitely been a lot smoother ride!

 

[fauconberg]

...i've got a 150PS AEB btw

 

[Matt82]

theoretically you shuoldnt gain anything, i suppose you could test for it but the gains ought to be minimal.

if youre not tuning the thing, id rather spend the money on making sure its in tip top health

 

[AB5QTS]

one thing i hate is the psychological dilema in the petrol station. 95ron is 119p/litre in most places, 98ron is 123p-125p a litre. its beyond some sort of psychological barrier and you feel its hard to justify it, but in reality 5p a litre more is only about £2 extra a tank (in the golf) and again not much more extra again in the audi.

My 1.8 TQS is mapped on 99ron and I used to fill up on it till recently. I used VPower which is now running at over £1.30pl so I've gone back to 95ron. Did notice a difference the first couple of tanks. I've got used to the power output now so no bother. I may treat myself every now and then.