What fuel for an Audi R8?
 

Met a guy at a Shell garage filling up his R8 today and noticed he was filling up with regular so I asked why he wasnt using the V power? "No point he said, waste of money. I tried it and got no difference in power and or economy."

So if he doesnt use it in his super car why is it supposedly better in a humble Impreza? I know that they are mapped for 98/99 but what is it about our cars that makes them better using this stuff that means they are mapped to this 'super fuel' in the first place?

All cars are different, some like this stuff, some don't. Saw a test in a magazine, I think Evo, regarding Super Unleaded. One of the cars they tested was an M5 V10, that got no benefit from V-Power either.

Personally I never noticed a difference with V-Power in my Impreza, but then mine was a UK Classic.

Its more so with turbo powered cars. The better octane in the fuel the less chance of detonation. Id say using higher octane fuel would be better regardless as its cleaner burning i think.

I remember seeing a motoring program a few years back (may have been 5th Gear), where they took a Scooby and a normal family hatchback and tested them on both types of fuel.

The 'super' fuel returned more power and better fuel economy for the Scooby, but made no difference to the other car. Quite why the Scooby preferred the super fuel, I have no idea.

FWIW, I run my Golf GTI (mk5) on SUL. Only ever ran it once on NUL, and got cr@p performance and woeful MPG :(
first and last time.

Would that not be because the ECU has adapted to except SUL. If you gave it a few tank it would probably settle down and then not be much difference.

Yes it was 5th gear. They tested something very basic (something like a clio), a Golf GTI and a Hawkeye STI. The test showed that the more initial power and the more performance orientated the car the more it benefits from V power, so it would be safe to presume that an Audi R8 would lap it up.

Anyone who has an R8 is obviously not short of cash so would need to be convinced there is no benefit to warrant not spending the relatively very small amount extra on the super fuel I would have thought.

I always though it was down to ignition advance. Unless the ECU is programmed (ie, at the factory or through a remap) to take advantage and adjust the ignition timing nothing is going to change.

I can tell the difference in my car.
If I use normal UL it'll only boost to 0.7 or 0.8.

With Super (98 ron) it will always pull to 0.9 as it should do.

Using normal UL won't do any harm however, as the ignition is just retarded by the ECU.

Perhaps the R8 driver bought the car as it looked nice and probably couldn't tell the difference in fuel in any performance car.

As an aside, I once put 3 tanks of the super diesel stuff in my pick up and couldn't tell the difference (169 bhp with power upgrade).

IMHO the guy is a mug, why not put good quality high octane fuel in your performance car :cuckoo:

TX.

I have to agree. After spending all that money for that performance I would want to be driving down the road knowing that I was using the full potential and keeping the engine in top condition regardless of whether I could 'feel' a difference or not.

On a side note, an Audi A3 Sline pulled up to cue behind it when there were 3 available pumps for the same side not in use (no they werent together). I wonder if it made him feel like he was driving a mini super car? :rolleyes:

Wow I'm among friends...... I have only used cheap supermarket fuel for years.

I've noticed f888 all difference!

See you all in the church hall on Tuesday

I thought Audis all ran on diesel? :confused:

Especially as Audi recommend 98 RON SUL. As that is the case then I suspect he will be running a retarded map with less power.

There again, I suspect very few R8 drivers ever use 100% TP.

Yes – I drive one and was under that impression too

And being the driver of one tried desperately to steer the conversation away from cars at the dinner party we went to last night, as our host (and neighbour) has a GT2 and a Ferrari 360 challenge stradale sitting in his garage

(incidentally he tried to tell me that his Porsche was the best one ever made – but thanks to this forum I know different)

Its a VAG thing; they aren't fussy on fuel (except biofuels).

My Golf R32 can run on any octane fuel above 95ron

It does say in the manual it will achive full power on super unleaded and a minimum of 95ron is acceptable, but a) Max power is at 6700rpm...I don't go there very often on a daily communte so would see little use in the power advantage, and b) its not any more efficient either.

If I used an R8 for a dialy driver, I'd still use 95ron if it gave no advantage, 5bhp extra bhp at 6500+ rpm is not worth the extra money - its still a quick car regardless of fuel. My NSX ran 95 RON. My Monaro VXR ran 95Ron, both my BMW 325 and 530 reccomended SUL, but ran on 95ron and my UK impreza ran 95Ron too (and still does).

You forget that 5th gear is NOT impartial. Its sponsorsed be it directly or indirectly by advertisers and companies with a vested interest. Just like the gadget show.

Product placement is worth millions is advert revenue.

Why leave it there Ali, probably still get 2* somewhere ...

TX.

Hmm, does that mean I don't need to use SUL on my M5? I always have because I've always felt that's what the beast would like. However in this day and age of increasing fuel prices I could save quite a bit of money using normal UL.

According to the owner's manual; 2 star is not suitable :razz:

95Ron minimum, so thats what it gets. :)

It also runs VAG 501.01 engine oil too (not by personal choice - thats what the dealers put in). Which basically translated is 10w-40 semi-synthetic, non-longlife. Which inccidentally is the very same spec oil the NSX and Scoob used to be filled with.

Jag on the otherhand runs 98 ron minimum; as that is the mimimum RON specified in the owner's manual, and its all open-loop EFi and mechanical vacuum/centrfugal advance ignition, so can't adapt without manual adjustment (can of worms and a reciepe for dropped valve seats).

When I had my 205 GTi it said in the owners manual to run it on 98ron petrol as it was the 1.9 not 1.6 model :wonder: This was for a car made in 1988 :freak3:

As I'm technically a 'young un' compared to many on here, was 98+ron petrol readily available back then?:freak3:

Yes - its was called 4star and thats what the jag used to run on before it was phased out :)

Ah, thanks for that. So 4 Star was leaded fuel yes? So running it on Unleaded wouldn't do the engines any harm??

Sorry, my faux pas, they have hadened valve seats (I got mixed up with the standard 205 XU engines ), so unleaded is fine.

Can't see why they need 98ron though; they only run 9.6:1 compression; the early 1.6s have higher compression and still run 95ron. Weird :wonder: Must be bad gas-flow design in the head.

From what I understand the Shell 95 (fuel saver) is now very similar to Vpower where engine cleaning/maintenance is concerned. That was the only thing that drew me to it in the first place, as my car cant take advantage of any potential power gains. No need to spend extra money at all now.:)

Although as higher octane fuel is more efficient at any engine speed it can also give a greater mpg so the extra cost can be outweighed by the extra distance covered.

I hope you put him straight ;)

MPG is partly down to calorific value of the fuel (how much bang per millilitre) in addition to its ability completely burn before the piston travels down too far (i.e how quick it burns). Alot of people think RON value is the key end-all of everything with petrol - it isn't, its just a basic measurement and not reflective of many other factors going on. In fact raising RON (purely for RON's sake) can make the fuel worse if its other attributes aren't condsidered with equal scrutiny:

With anti-knock and "cleaning" additives, some of these chemicles take place of the actual raw fuel - lowering its calorific value. Or making it burn slower. In lamens: Its a balancing act. Leaded fuel was good as it had good calorific values AND good anti knock properties, whilst giving a good burn speed. Super unleaded burns slower even if its the same RON as leaded, it can also be more difficult to ignite. I personally suspect SUL has lower calorific value to leaded fuel too, due to the additives used to raise its anti-knock values.

In worst case scenarios; A fuel that burns too slow may not be fully burnt after the piston is well on its way down the bore- this is wasteful. A high RON is difficult to ignite; stressing ignition components and only getting partial burn of the fuel, again wasteful (which is why we have coil packs and iridium/platinum plugs these days). The amount of additives added and their own calorfic values affects the amount of fuel required to be injected to get the same motive power.

Typically fuel companies don't tell us that openly the full properties of their fuel except marketing certain properties (namely octane).

Shell fuel saver probably just has a higher calorific value to the previous 95Ron it replaced, despite it being the same RON value. Therefore less quantity is needed to do the same amount of required work.

Its somewhat similar in theory to mixing 2 stroke premix; the amount 2 stroke oil added actually affects how lean/rich a 2 stroke engine runs, the mixed fuel's calorific value and its burn speed; the more oil (additive) in the mix, the less fuel there is to burn per millilitre injected. OK, additives in 4 stroke fuel don't really affect the AFR (well ok, oxgenates do), but in lamens it dilutes it, sometimes with positive gains, but at the cost of some other attributes.

All good stuff - but does not answer the question I posed.

Do think the only benefits of 98RON fuel is a small increase in peak power?