Going from Super Unleaded to Unleaded

aj23_2

I have an Audi S3, it's three and a half years old. From day one, I've put Super Unleaded in.

It's currently averaging 34.2mpg (though it's winter) which gives me about 415 miles of range. In the summer it goes up to nearer 35mpg, which can give me about 480 miles of range. Which is very good for a 300hp car, 2.0L Turbo.

I live in an area where in the past 6 months, the price has averaged between £1.20 and £1.30, though I use PetrolPrices.com to monitor, and if I'm driving past a station which is cheaper, I always fill up.

I was wondering if it would damage my tank or engine if I go to using Unleaded, to make filling up cheaper, as I'm doing more longer trips, or is my computer and engine used to the cleaner fuel now?

My previous car, a Mini Cooper S, I started using Super Unleaded half way through having it, and I started getting about 100 miles more range from the tank. That car when I sold it was averaging 46mpg.

I already do what I can: I don't turn on heating controls or A/C for the first 2/3 miles of driving to let the engine warm up, Below 50mph I have windows open in summer, above I use A/C to avoid drag, I drive at 60 on motorways, always use cruise control for any speed if it's a long and straight road, I use Audi Drive Select Efficiency Mode on longer straight runs with cruise control etc.

I'm currently filling up once every 2 weeks, about £55-£60 a time. In 2018 I spent £1650 on petrol, above the national average.

AdrianC

Why buy a high-performance car if you're going to drive like a granny to try and save every possible drop of fuel?

That aside, what's the difference between Super and Premium Unleaded. One thing... Increased octane. Premium is 95RON in Europe, Super is 98RON. (Ignore anything US-based, because they measure octane differently, and they have different pump standards.)

What does increasing octane do? It increases the resistance of the fuel to ignition. Yes, that's right. It makes it harder to light. The benefit there is that you can advance the ignition without risking pre-ignition, pinking. That means that the power stroke can start a tad earlier, which is more efficient at pushing the piston down the bore. On forced-induction engines, you can increase boost without risking pre-ignition, again increasing the efficiency at pushing the piston down the bore. That efficiency means greater power for less fuel. At part-throttle, that means the same power for smaller throttle openings, which means better fuel economy.

So the question is whether the car is set up to ONLY use Super, ONLY use Premium, or adapt for the two. Are there warnings on the filler cap and all over the manual not to use Premium? No? Then we can rule out Super-only.

If the ignition and/or boost don't adapt, there is zero difference. High-performance stuff like an S3 or Cooper S will adapt.

But if you're just pootling, off-boost, then the difference will be absolutely minimal. It will certainly be a smaller percentage than the increase in the cost of the fuel, and will be massively outweighed by any increased journey needed to buy Super.

Now, let's look at the numbers you give...

34.2mpg = 415 mile range
35mpg = 480 mile range
That doesn't make sense.
415 miles at 34.3mpg = 55.1 litres
480 miles at 35mpg = 62.3 litres
So, yes, putting more fuel in will take you further...
35mpg on 55.1 litres = 424 miles.

As for "100 more miles of range" - assuming an R56, that'd be two miles per litre from the entire capacity of the 50 litre tank. 46mpg is almost exactly 10 miles per litre, so you're claiming a 25% increase in fuel economy at worst. Yet the Audi has, on your figures, given you just a 2% increase. And we already know from the Audi range what your basic mathematical skills are like.

Navigator123

Unless you are driving a supercar (Lamborghini, Ferrari, Audi A8, or the suchlike) then you should not be using Super Unleaded as it makes the engine work harder, uses more oil and returns a lower mpg than the 'cheap stuff'.

I tried it on my car and found my mpg on normal unleaded was around 41 mpg (mixed driving around 120 miles per week) and 38mpg on the Super Unleaded. And it was costing me around £5.00 more per tank to fill.

Now it is only the cheap stuff that goes into the tank and the car seems to be perfectly happy some 3000 miles later and my oil consumption has dropped to next to nothing.

alan_d

AdrianC wrote: »

Why buy a high-performance car if you're going to drive like a granny to try and save every possible drop of fuel?

My thoughts also.

In my experience in several 'average' petrol & diesel cars being driven 'normally', 'super' fuels increase the MPG, usually just about enough to offset the additional cost.
I've not calculated the figures in my only 'powerful' petrol car, but as MPG isn't really a concern in that I can't be bothered! Premium fuel seems to help with power delivery though

AdrianC

Navigator123 wrote: »

...you should not be using Super Unleaded as it makes the engine work harder, uses more oil and returns a lower mpg than the 'cheap stuff'.

This is complete and utter codswallop.

bengalknights

If you do need super unleaded do you have a local costco petrol station near you, can save you a bit in costs minus membership fee.

aj23_2

AdrianC wrote: »

Why buy a high-performance car if you're going to drive like a granny to try and save every possible drop of fuel?

That aside, what's the difference between Super and Premium Unleaded. One thing... Increased octane. Premium is 95RON in Europe, Super is 98RON. (Ignore anything US-based, because they measure octane differently, and they have different pump standards.)

What does increasing octane do? It increases the resistance of the fuel to ignition. Yes, that's right. It makes it harder to light. The benefit there is that you can advance the ignition without risking pre-ignition, pinking. That means that the power stroke can start a tad earlier, which is more efficient at pushing the piston down the bore. On forced-induction engines, you can increase boost without risking pre-ignition, again increasing the efficiency at pushing the piston down the bore. That efficiency means greater power for less fuel. At part-throttle, that means the same power for smaller throttle openings, which means better fuel economy.

So the question is whether the car is set up to ONLY use Super, ONLY use Premium, or adapt for the two. Are there warnings on the filler cap and all over the manual not to use Premium? No? Then we can rule out Super-only.

If the ignition and/or boost don't adapt, there is zero difference. High-performance stuff like an S3 or Cooper S will adapt.

But if you're just pootling, off-boost, then the difference will be absolutely minimal. It will certainly be a smaller percentage than the increase in the cost of the fuel, and will be massively outweighed by any increased journey needed to buy Super.

Now, let's look at the numbers you give...

34.2mpg = 415 mile range
35mpg = 480 mile range
That doesn't make sense.
415 miles at 34.3mpg = 55.1 litres
480 miles at 35mpg = 62.3 litres
So, yes, putting more fuel in will take you further...
35mpg on 55.1 litres = 424 miles.

As for "100 more miles of range" - assuming an R56, that'd be two miles per litre from the entire capacity of the 50 litre tank. 46mpg is almost exactly 10 miles per litre, so you're claiming a 25% increase in fuel economy at worst. Yet the Audi has, on your figures, given you just a 2% increase. And we already know from the Audi range what your basic mathematical skills are like.

You might call it driving like a granny, I call it being sensible. My car, if I having it Auto or Dynamic and throttle the peddle, can see the range drop in numerals of 5 every minute or so. I drive sensibly to conserve petrol because even driving normal can use a lot. It is Audi's higher performance of the standard A3 line, don't forget. It also has Quattro, so it has an All-wheel drive system which uses petrol constantly to power it and is always on.

Regarding my figures, it does make sense. I'm only saying what comes up on my dashboard. Using Super does seem to give more range, it does keep your engine cleaner and it can improve performance.

What I'm asking hasn't actually been answered: the consequence of switching from Super to Unleaded as the car is obviously used to having Super run through the system.

alan_d

aj23 wrote: »

What I'm asking hasn't actually been answered: the consequence of switching from Super to Unleaded as the car is obviously used to having Super run through the system.

There is no consequence - just stay away from supermarket fuel.

aj23_2

Navigator123 wrote: »

Unless you are driving a supercar (Lamborghini, Ferrari, Audi A8, or the suchlike) then you should not be using Super Unleaded as it makes the engine work harder, uses more oil and returns a lower mpg than the 'cheap stuff'.

I tried it on my car and found my mpg on normal unleaded was around 41 mpg (mixed driving around 120 miles per week) and 38mpg on the Super Unleaded. And it was costing me around £5.00 more per tank to fill.

Now it is only the cheap stuff that goes into the tank and the car seems to be perfectly happy some 3000 miles later and my oil consumption has dropped to next to nothing.

Probably because you need to do it for longer over a period of time for it to get used to it and adapt. It's generally recommended that every third or fourth fill, to put in a half tank of Super to clean the engine out.

aj23_2

alan_d wrote: »

My thoughts also.

In my experience in several 'average' petrol & diesel cars being driven 'normally', 'super' fuels increase the MPG, usually just about enough to offset the additional cost.
I've not calculated the figures in my only 'powerful' petrol car, but as MPG isn't really a concern in that I can't be bothered! Premium fuel seems to help with power delivery though

Well this is it, the power in my car is instant and quick. It's a 4.7 second 0-60 car. Only a 2.0L Turbo.

aj23_2

alan_d wrote: »

There is no consequence - just stay away from supermarket fuel.

I avoid Shell and BP. have done for years. They overcharge more than Tesco, Sainsbury's etc by as much as 15p per litre. Shell and BP supply the supermarkets anyway.