Super Unleaded -v- Unleaded

smemon · 04-08-2006 2:26pm #1

rolling up to a garage today, que in the two unleaded pumps so i said feck it, i'll get super unleaded.

i've always thought unleaded is the cheap and cheerful option and super unleaded is for guys in merc's and jag's who have €€ to burn.

is there really any difference in the average car? apparantly super unleaded is cleaner, thus desposits less residue and uses more of your fuel. so if this is true, surely you'd get more miles per gallon over unleaded and possibly save in the long run

Stark · 04-08-2006 2:53pm

My car manual says there's no advantage of super unleaded over normal unleaded.

btkm8unsl0w5r4 · 04-08-2006 2:54pm

I also have wondered about this? Is it really worth the difference re performance, engine wear etc? I only want to feed my car the best but with the price of fuel these days I dont know if it can be justified.

zuutroy · 04-08-2006 2:55pm

I use Shell V-Power. It adds enough MPG to easily cover the difference in cost. I find the car runs smoother, and is a little bit more responsive. However, my car is 15 years old...not sure of the benefits in a newer car

Slinky> · 04-08-2006 3:12pm

Its only necessary in Tuned Turbo cars normally Jap imports AFAIK, The higher the RON 95/97 (or 93 in the states) means it combusts at a higher temperature.

In a highly tuned car there is a possibility that the fuel would ignite before enterering the ignition chamber ,then air woul be forced in with no ignition destroying a piston, So they adjust the timiing for 95 oct or use a super /race fuel what ever

Im sure there's someone on the board who knows a lot more about it than me can comment further

Squirrel · 04-08-2006 4:08pm

Some cars get no benefits from the higher octane, and in some cases performance gets worse due to the ecu being set up for 95 octane fuel. There was a test in a recent Auto Express, I'll try find it and post the results

alastair · 04-08-2006 4:12pm

Super-unleaded makes a noticable difference in some classic cars with a thirst for higher octane fuel. I've a '73 volvo, and that Shell Optimax is the best I've found for it.

Squirrel · 04-08-2006 4:19pm

Vauxhall Astra VXR

Regular (95RON) - £0.949 - 213.5bhp
BP Ultimate (97RON) - £1.009 - 209.7bhp
Shell Optimax (98RON) - £0.979 - 222.2bhp
Tesco 99 (99RON) - £0.999 - 221.3bhp

VW Polo 1.2

Regular (95RON) - £0.949 - 70.7bhp
BP Ultimate (97RON) - £1.009 - 66.2bhp
Shell Optimax (98RON) - £0.979 - 69bhp
Tesco 99 (99RON) - £0.999 - 69.4bhp

The rolling road used in the test has an accuracy of +/-1bhp

The result said that only cars whose engine management systems adjusted got benefit, like the Astra (except on the BP fuel) but others such as the Polo got no benefit.

This issue was the 14th-20th of June so prices were correct then.

Says nothing about efficiency though

DaveD · 04-08-2006 4:31pm

smemon wrote:

rolling up to a garage today, que in the two unleaded pumps so i said feck it, i'll get super unleaded.

i've always thought unleaded is the cheap and cheerful option and super unleaded is for guys in merc's and jag's who have €€ to burn.

is there really any difference in the average car? apparantly super unleaded is cleaner, thus desposits less residue and uses more of your fuel. so if this is true, surely you'd get more miles per gallon over unleaded and possibly save in the long run

Where did you get Super Unleaded ?

Mayshine · 04-08-2006 5:16pm

DaveD wrote:

Where did you get Super Unleaded ?

Please tell me too - I'm also looking for the stuff.

Stark · 04-08-2006 5:25pm

You get it in pretty much every petrol station in the country.

bazz26 · 04-08-2006 6:46pm

Stark wrote:

You get it in pretty much every petrol station in the country.

Most petrol stations in Ireland only sell 95 RON afaik. The "super unleaded" petrol you see in petrol stations here is not 97/98 RON afaik.

97/98 RON (better known as super unleaded) is common enough in the UK but very rare in the Republic as it is just too expensive and there is not enough demand for it. Mostly high performance cars benefit from 98 RON to my knowledge.

04-08-2006 7:40pm

Just to clarify,was it super unleaded you bought or shell V power?

Super seems to be like hen's teeth but people are crying out for it

SouperComputer · 04-08-2006 8:05pm

This has been done to death.

Anyway, ill repeat myself for those who had better things to do and didnt catch my last octane rant......

Contrary to popular belief, a high octane rating does not mean more oomph, bang or wallop.

In fact the opposite is true. The presence of octane in simplfied form, changes the time it takes for the fuel to burn. Higher octane fuels generally take longer to burn and burn at a lower temperature.

So why do high powered engines use it you say? Well the reason that these engines produce a high output in comparison to their capacity it that amongst other things, they run higher compression (generally, im simplifiy here!) or forced induction eg turbo or superchargers.

Using a lower octane with high compression causes dentonation or pinking. Basically the fuel\air mix ignites before the spark plug fires. This results in a metallic "pinging" noise, overheating and a rather nasty hole melted in the centre of the piston!

With the higher octane fuels the burn time is more controlled and as a result you can create and engine that puts out more power per unit capacity.

Bear in mind however that its not neccacrily high power engines that prefer 98RON, its to do with how highly tuned the engine is. IE a 300BHP 6L engine will run on 95 or even 87RON with no issues, a 125BHP 1.0L engine would die very quickly though unless the is ECU is mapped to cope.

So long story short, unless your car is mapped to run better with 98RON, you will find no difference except in engine temperature. But the difference is so small that it would not be noticeable on most gauges.

An extreme example of this can be found in drag racing, the engines produce over 500BHP per 1.0L. However they use alcohol as a fuel as it burns at a very low temperature. As a result they can use crazy compression rates and massive superchargers.

Kersh · 04-08-2006 8:45pm

well said Souper. In older cars, the timing needs to be manually advanced slightly to use the gains of higher octane petrol anyway. Like in our F. Vees. Its no good if you dont adjust the timing!!

nialler · 04-08-2006 9:44pm

Souper hadn't a clue what you just talked about there but

shell optima/V Power = runs like a dream
shell/maxol 95 normal - no power at times (could be the MAF)

S320