POLL: What fuel do you use?

[markos]

Just interested to see what everyone uses after a discussion with another mk5 gti owner about fuel type and power vs wallet. 98 is what's recommended, but what can people actually afford to fill up with?

[th3_f15t]

I use Tesco Momentum fuel, as it makes a noticeable improvement to how the engine operates and performs. I get about 30-50 miles more per tank compared to standard fuel. The price difference per tank is not worth worrying about over the improvements you'll see.

[J400uk]

Generally just 95 stuff, normally Shell and sometimes Sainsburys. I found using premium fuel made the MPG noticeably worse around town which didn't suit me as that's where I do most my driving.

[lucky_se7en]

Use shell v-power currently on mine. Had filled it with standard 95 a couple of times before then.
Not sure if it's psychological,but I definitely feel a smoother running of the motor on v-power.

[tea2112]

I use Tesco Momentum 99 fuel

[Chris MKV]

Tesco's 99

[Niallt1892]

I use shell v-power nitro

[jonnyb]

I did a few tests over several tanks of fuel.  Very different to get solid results as there are a whole host of variables, however i saw some interesting trends.

Firstly, the car idles and runs smoother in low revs on any performance brand (Shell / Momentum).  I've heard that the car can take several tanks to adjust to which ever fuel you've changed to, so perhaps this went against the 95ron when i switched to that.

Secondly, general pickup and sense of power is greater with the super unleaded.  Very open to mind games though, so perhaps don't take that as gospel.

Thirdly, i track all fuel expensed on my phone.  I happen to do very regular runs, so my variation on driving styles remains fairly constant.  I found premium fuels gave me 30-40miles more per tank.  I get around 310 with 95 ron.  Around 340-350 Tesco Momentum.

Say thats a gain of 30 miles. That's circa 10% better mpg. 

Standard Fuel costs*  : £1.30 per litre. 
Premium Unleaded costs: £1.38 per litre

That's an increase in price of roughly 6%.

10% - 6% = 4%

To sum it up, you gain an extra 4% economy (at least i do), and you also get a car which feels faster, smoother, and probably makes the car feel warm and fuzzy inside.

Hope this helps

*taken from http://www.petrolprices.com/

[th3_f15t]

That's a good write up there, even accounting for the many variables and the bias towards final results, still pretty valid findings.

A bit of science...

The reason you get a smoother running engine with higher octane is due to the way it burns in the engine. A higher octane fule actually burns at a lower temperature and for longer than a lower octane fuel (needs more oxygen compared to an equal amount of lower octane fuel). This explains two of the major points you mentioned.

Firstly, economy. The reason you theoretically get better MPG from higher octane fuel is for at a given point in the power output of the engine, a smaller amount of high octane fuel is needed with the same amount of oxygen as lower octane fuel but still releases the same amount of energy, thus meaning less fuel is required per reaction leading to better economy.

Second, the "feel" of the engine. Because high octane burns at a lower temperature, the heat generated is more easily dispersed away from the ignition chambers. This means that un-burn fuel in other chambers that are awaiting ignition or exhausting do not ignite out of turn (the effect of burning out of turn is known as engine knocking). Because the engine is allowed to fire in the correct sequence constantly, the energy output from each combustion reaction is more efficiently used in moving the car.

This is a really basic overview of the science of fuels, and I'm not overly sure it's completely accurate, but from what research I've done this is the conclusion I've drawn up. I'm open to critics...

[jonnyb]

At the end of the day it's always going to come down to personal preference. 

If i was using Shell V-Power, i'd probably be skint, but the Tesco Momentum isn't much more than regular 95 RON.  I'm happy to pay slightly more each fill up, based on my own personal findings of running both types of fuel. 

I'd suggest other people also try each fuel over the course of a few months, and make their own minds up.  Some will like it, some wont.

If it comes down to 'I can't afford premium unleaded', then perhaps a Gti isn't the right car to have either.