Hi all,

dont know if this has been aksed already or not.

Is it worth paying out that little extra for the super unleaded over regular for my 4.2ltr supercharged RRS?

Does any know how many extra miles it would give me per tank?

Thanks

Hi captain and welcome, I think you've opened a real can of worms with this one. Though I'm coming from the diesel side I only use the good stuff , nobody can prove it either way but if it helps clean the fuel system then Its less wear in the injectors which makes them last longer then I'm happy to pay a little more at the pump. 2008 G4 RRSport TDV8 current
2009 TDCi 90 current
2018 Discovery 5 HSE lux current
1994 Dakar current

I have not got a rrs yet but im my bmw petrol i dont get any more mpg to be honest but it is a lot smother when underload and at idle and when ever i change the plugs there never black or nothing. So i dont think you get any extra miles as petrol is concerned but deffinetly worth the extra pennies imo

All my Sports have been run on the Shell VNitro + fuels both Petrol & Diesel - a few pennies more for piece of mind IMO but still can't find any real hard evidence that it makes a difference BUT can't believe it can be advertised has having those extra properties if it DOESN'T  16MY Estoril Blue SVR.............
17MY Autobiography Dynamic - Corris Grey - WOW.
14MY Autobiography Dynamic - SDV6 - Fuji White
12MY Autobiography - SDV6 - Santorini Black - Dual View - Rear Entertainment - Sunroof.
12MY Autobiography - SDV6 - Orkney Grey - awesome ;(
2005 Java Black - 4.2 V8 Supercharged First Edition- will never be forgotten ;(

Funnily enough I watched fifth gear last night and they were testing premium unleaded vs cheaper unleaded. There was a 4 bhp difference between the most expensive and Asda fuel which VBH said she could feel. This was tested on a 250bhp VW golf.

Her conclusion was it wasn't enough of a difference to pay the extra.

It was unleaded they tested not diesel though. 2015 RRS AB SDV6, Fuji White, Ivory
2012 RRS HSE SDV6, Sumatra Black and Ivory
Audi A5, 3.0 TDI, Gone
Audi TT, 3.2 V6, Gone
BMW 5 series tourer, Gone

I was told by someone who should know about these things that it's not worth it for petrol unless you are chasing the last couple of hp, but for diesel engines that have a DPF it is well worth spending an extra 10p/litre, especially if driving something like an Audi which you can't regenerate and have to pay £1500 for a new one when it becomes blocked.

ChrisWinstone wrote:

Funnily enough I watched fifth gear last night and they were testing premium unleaded vs cheaper unleaded. There was a 4 bhp difference between the most expensive and Asda fuel which VBH said she could feel. This was tested on a 250bhp VW golf.

Her conclusion was it wasn't enough of a difference to pay the extra.

It was unleaded they tested not diesel though.

I have a 4.2s/c here in Aust.
We have three basic levels of unleaded at the moment. (91/2 octane, 94/5 octane (some with 10% enthnol) and 98 octane.
From the previous posts I don't know what octane rating your petrol is but generally speaking RRS S/c should be running at least the 95 octane. For the last few years in Australia 95 octane has been cheaper than Std unleaded and 98oct has been A$0.20c a litre dearer. So I tend to run a mix of 95 & 98oct.
We have just started to see 'Extra Premium unleaded' 98 oct. supposely with 'This and That' additive/s but at an extra cost of course.
They are trying to be or seem different to the discounters in our market so they can justify their higher prices.
Mine will run fine on 95oct(10% ethanol) but I mix in the 98 oct. in because RR in their wisdom does not specify that 10% enthanol is Okay. Not in my 06 model anyway.
Most other cars here say its okay and we also have modern cars that are made to run on 85% ethanol.

Premium fuels are a way of extracting more revenue from people who can afford it, whilst not losing the customer on a lower budget to cheaper competition. Analogous to Grande vs Venti in coffee shops or first class travel. Or HSE vs Autobiography. So massive opportunities for profiteering.

I always use premium diesel on every tank because I believe the cleaning agents will help with reliability. When my mileage was higher and running petrol I would go premium in one in every 2 to 4 fill ups. Every little helps. L405 P400e Autobiography (MY2020)... Silicon Silver / Espresso
RRS TDV6 HSE Lux (MY2011)... Nara Bronze / Arabica - now gone!

I think that using a filling station that is busy is more important than the octane rating. If you put in ultimate or v power that has sat in the tanks for a long time it will have lost its benefits.
Terry

In case of a supercharged petrol the only thing important is how much can the engine ECU advance the timing. In a supercharged car (boost is relatively low and very predictable with the RPM) the ignition maps are safe for ~95 RON/MON octane fuel and IIRC - correct me if I'm wrong - the RRSC ECU allows for some ignition advance, however in no circumstances, no matter what fuel you put into the tank, it will not develop more than stock HP, because in order to extract more HP, ignition advance must be pushed beyond the capabilities of the stock ECU. An ECU program upgrade by itself will not extract more than 5, maybe 7% power from a RRSC (no boost change). Change the boost (think: smaller pulley) AND the ECU software, and you'll see 10, 15% increase in HP if the fuel used is high-octane: more boost, more ignition advance, high-octane prevents detonation, profit.

As said, higher-octane fuel is a little bit more detonation-resistant than regular, so there is a slight possibility that the engine will try its best and run maximum ignition advance allowed by the ECU (read: will make more power from the same amount of fuel). Doing the math quickly and dirty it seems to me that using fuel with more than 95 RON/MON will give no more than 3~5% range increase. Not worth it IMO. And if you want to keep your injection system clean, there's better stuff to add once every year or two to the tank of fuel. Regards etc.,

Wojtek

---
WAS: 2006 RRS Supercharged
IS: 2010 RRS TDV8 HSE