I've had my vrs tsi for about 2 months, and have always filled up using tesco 95 RON. Since I've had it acceleration between 1500 and 2500 rpm was a bit ropey, hesitant sometimes, and just assumed it was either my driving style, traction control or the ecu.. I put Tesco 99 RON yesterday, and I no longer experience the ropey acceleration !.. so can only assume the grade of fuel played a part in this. Anyone else experience this ? I may even try shell V-Power to see how the car responds to that !

Edited 15 November, 20169 yr by Leeboy22001

My previous car, an Audi RS4, came with a recommendation in the manual to run on 98 octane (95 in emergency was OK) so I ran it on either Tesco 99 (or Momentum as they used to call it) or Shell VPower.

 

I found the running was slightly better (smoother at low revs and more responsive) on Tesco 99 than on VPower but the difference was very small even after I had a custom remap done.

 

Some tuners would recommend VPower and some Tesco 99 so it seems more a case of price and/or convenience which one to use.

Edited 15 November, 20169 yr by PetrolDave

I also run my petrol cars on tesco 99 and every now and then drop a redex in too.

When I ran my mk2 fabia vrs on 95 that ran lumpy as f..k when 99 wasn't available

It certainly runs smoother with 99 ! , am hoping mpg may improve a little too

Can't say I've noticed any lumpiness or hesitancy with either Asda 95 or Tesco 95. My previous MK2 FL TSI was also exclusively filled up on either of these too. Aren't these mapped for 95 out of the box anyway?

It does say minimum 95 RON on the petrol cap, so yes. It may just be highlighting an issue ?

Can't say I've noticed any lumpiness or hesitancy with either Asda 95 or Tesco 95. My previous MK2 FL TSI was also exclusively filled up on either of these too. Aren't these mapped for 95 out of the box anyway?

We've had 5 cars remapped & they were all optimised to perform properly on 95 octane, 'cos that's all we can buy in this town. 

All of them felt much nicer to drive after the remap so we felt that they never needed 97 or 98.

 

It's only the R that has 98 as the recommended fuel, the other two are supposed to be ok on 95.

Again, they all run well, & the R tolerates 95 too.

 

DC

We've had 5 cars remapped & they were all optimised to perform properly on 95 octane, 'cos that's all we can buy in this town.

All of them felt much nicer to drive after the remap so we felt that they never needed 97 or 98.

It's only the R that has 98 as the recommended fuel, the other two are supposed to be ok on 95.

Again, they all run well, & the R tolerates 95 too.

DC

It's funny how engines react...my Mk2 FL TSI was remapped by Shark, and it used to run brilliantly on 95, and I'd be damned if I could tell the difference on premium 97/99 fuels.

My S2000 however, putting 99 in that was like night and day, used to react so much better.

I'm pretty sure the vRS recommends Super unleaded (that's what it says on the petrol flap anyway)

Edited 16 November, 20169 yr by NikEd

I'm still on my first tank of fuel for a newly bought 1.4TSI Combi MkIII, manual gearbox. My first experience of a direct injection petrol. I know it also says 95 octane minimum on the fuel flap. Is this engine's management clever enough to adapt to differing octane levels? I will also try to avoid supermarket petrol. Our higher octane stuff around here tends to be Total. I'm very impressed with the flat torque curve, so far, and tend to drive it like my previous diesel Octavia.

I know it also says 95 octane minimum on the fuel flap. Is this engine's management clever enough to adapt to differing octane levels?

VAG FSI engines (at least when fitted to Audis) used to say minimum 98 RON so it was a pleasant surprise to see that my 1.4FSI Octavia said 95RON on the filler flap.

 

All modern engines are fitted with knock sensors so that they can back off the timing to prevent pinking (pre-ignition), whether the timing can be advanced far enough to take advantage of 98RON vs. 95RON depends on the details of the ignition/injection maps. But using 98RON can't do any harm, and if there is a noticeable improvement in running and/or performance then a judgement can be made whether the extra cost is worthwhile.

 

One further thought - it always used to be said that 98RON fuels also had a lower sulphur content than 95RON fuels, which meant that with 98RON fuels a purge cycle for the catalytic converter (which burns extra fuel to increase the exhaust temperature and burn off the sulphur by-products caught in the cat) would happen less often and this COULD mean that mpg on 98RON was around 10% better than on 95RON - but I don't know if that's still true or if it applies to the Octavia 3?

Edited 16 November, 20169 yr by PetrolDave

I'm pretty sure the vRS recommends Super unleaded (that's what it says on the petrol flap anyway)

 

It does, however I think that is down to some countries referring to their 95 RON unleaded as Super, and their 98 RON as Super Plus

Ahhh got you

Tesco 99 and shell v-power should, in theory, give the same or very similar performance as both have a RON of 99. The difference would be the additives to clean internal components.

Personally I run mine on Shell V-Power. I've used normal shell once one a tank and the fuel consumption dropped a fair bit (by 3mpg over the tank). Although that's not a scientific experiment as there are always other factors.

Best for consumption was ESSO 99 rated fuel (can't remember what it's called).

Not tired Tesco fuel as I've not used them since the diesel issue years ago.

In Australia the standard fuel is 91 Octane but none of the VAG cars are designed to run on it although most of the standard Japanese, Korean and local built cars do.

I use the recommended 95 Octane in my mk3 1.4tsi.

I tried a few tanks of 98 Octane (I think that is the highest generally available here unless you go all Ethanol) and there was no discernable improvement to power or consumption so I just changed back.

Edited 16 November, 20169 yr by Gerrycan

I run 99 Ron to get higher MPG !!!

I use Sainsbury's super unleaded (97) not spoilt for choice round here without traveling a fair way.

I have Tesco, Shell or Esso within a half mile radius, so am spoilt for choice!

Does the car/Skoda recommend a particular brand - I know my Ford "recommends" BP on the petrol cap, can't remember which RON however. It rarely gets any however as BP is pretty much the only garage of which there isn't one too locally, loads of others about. In said Focus I have occasionally filled up with higher RON when I have long journeys planned, I like it think it manages a greater range per tank, but that may be just wishful thinking

Petrol/Air mixture with an Higher Octane Ie 98 or 99 RON benefits the engine by being able to be compressed to a higher pressure before ignition, higher pressure more power, me thinks

From what I know, the compression ratio is fixed(10.5:1), regardless what octane you refuel.

Does the car/Skoda recommend a particular brand - I know my Ford "recommends" BP on the petrol cap, can't remember which RON however. It rarely gets any however as BP is pretty much the only garage of which there isn't one too locally, loads of others about. In said Focus I have occasionally filled up with higher RON when I have long journeys planned, I like it think it manages a greater range per tank, but that may be just wishful thinking

That's a huge can of worms.

If Ford say that, they should say, explicitly, why they do and what the implications are if you don't. I suspect, however, that there is absolutely no basis from an engineering perspective, why Essso is more 'compatible', and that it's just a joint promotion venture. Otherwise they would have to make some specific claims which would need empirical evidence to support that claim and other manufacturers of fuel would be paying very close attention to what Ford and esso claim.

Petrol/Air mixture with an Higher Octane Ie 98 or 99 RON benefits the engine by being able to be compressed to a higher pressure before ignition, higher pressure more power, me thinks

As has been said the compression ratio is fixed, but the benefit of a higher octane rating is the ability to ignite the mixture earlier without causing pre-ignition (pinking) - it's this longer more complete burn that generates extra power.

Let's see if I understand, if not, please correct me: high octane is useful at frequent WOT, summer high temperatures, high engine loads, when knocking phenomenon can occur due these conditions. If we drive normal, 95 octane will be enough. Am I wrong?