Mk 8.5GTI - What Fuel

[WebRoP]

Hi all, Got an 8.5 GTI coming end of Feb, will this need the higher grade of Petrol (97/98/99 octane etc) to run properly ?

[fredgroves]

No it runs on e95

[BillSan]

I've got a Mk8 rather than a 8.5.  Ran it on 97/98 RON when I first had it and didn't notice any difference from when I ran on 95.  Has run perfectly well on 95 for 42,000 miles now and I've probably saved a few hundred £.

[Dav3smith]

The true answer here is it will run on any type of fuel (petrol of course) from the pumps at a UK petrol station.

Now the big question is if there are benefits from using higher RON rated fuel such as 97/98/99 over the standard 95. Now this is a rabbit hole where various benefits from using higher rated fuel are listed as better lubricating properties, prolonged engine life etc. Now personally I'm not sure if any of this is true but there will be plenty of people who have opinions on this matter and maybe there is some evidence out there.

Personally I use Shell V power or Tesco Momentum as they are both 99 Ron and I figure if I'm paying for the higher grade I may as well have the highest I can get. I'm really not sure I'm getting any benefit apart from the placebo effect.

One final point the benefits may be there if you're doing time trials or racing but for the school run or sitting in day to day traffic I'm certain I'm just boosting the profits of the petrol stations and my car runs just the same. I certainly can't tell any difference apart from less money to spend on over priced chocolate in the forecourt shop.

[Adam T7]

You have basically and succinctly described my thought pattern😀

[Peter_booker2003]

TCR owner here but in my opinion you can definitely tell the difference when it's running on 95 or 99. I'm not a racer but it's simply smoother with 99 in it for me.

For me if you are buying a new Mk8.5 then the extra couple of pounds per fill up isn't going to be game changing.

[Paul70]

It’s proven that higher octane allows an engine to run more timing advance and as a result make more power. Ever since the MK5 GTI VW have optimised their engines to run on higher octane fuel. You can run lower octane fuel but the ECU will retard timing and you will lose power and responsiveness. Of course on a school run and around town this is irrelevant but when the opportunity arises and you can stretch the car a little, I personally would like the car to run as designed. Why else buy a GTI 😊

I would always chose (and recommend) to run 99 Octane fuel but it’s personal choice at the end of the day.


Also there have been numerous tests proving higher octane fuel results in better MPG, so the cost difference in negligible

[DrivenToDistraction]

Also there have been numerous tests proving higher octane fuel results in better MPG, so the cost difference in negligible

Yep, the claimed improved mpg of premium (98/99 RON) fuels is key when calculating the overall costs. It is not difficult to find claims of 10-15% improved mpg (compared to 95 RON) when using premium fuels in high performance cars with turbos. Some of these test were not strictly scientific, but leaving that aside, if you assume the more conservative estimate (10%) a driver doing 8000 miles per year would actually save about £60 per year by using the premium fuel. If there was no difference in mpg between the fuels (there are of course loads of factors that affect the mpg that an individual driver achieves), then the extra cost per year for the premium fuel would be about £100.

As said, these sort of annual costs (even assuming that the premium fuel may cost you a bit more overall) are not usually big concerns for drivers of performance cars who are convinced that the car feels smoother/more responsive running on the more expensive fuel.

[WebRoP]

Thanks for the responses. Very interesting and definitely food for thought

[Jonfigo]

Watched this this morning, pretty much answers the question. I've always wondered the same.

https://youtu.be/Pwk_u71Izpg?si=DUrJLgi1bYD3PJJ7