SuperUnleaded over Unleaded Petrol?

[UseItNow]

As the title suggests fellow Hexites, is there any difference between SuperUnleaded and Unleaded petrol apart from the price per litre of course.
Will there be a MPG difference between the two and finally will the use of the SuperUnleaded (BP Ultimate, actually) make a difference in a new car?

Thank you all in advance for your comments and wisdom!

[kalniel]

Super unleaded is normal petrol these days.

BP ultimate and Shell V-Power etc. raise the octane level and increase the detergent content, so they can help clean out older engines but won't really do anything for new cars.

[Funkstar]

Depends on the car. There was a huge thread on this a while back.

My golf GTI doesn't like basic fuel, it "pinks" on idle. I use ultimate all the time unless I can't get any and am desperate to fill up.

EDIT: Here we go - http://forums.hexus.net/hexus-automo...mal-fuels.html

[Jay]

I use Texico super on my Mazda Roadster, it seems to like it more.

[Fraz]

As I understand it, only bother to use the Super-Duper extra amazing unleaded if your engine requires 97/98 RON petrol (for pinking/knocking reasons). Otherwise just get the normal stuff.

The claims that you get more miles per gallon for the more expensive fuel are basically lies. What Car magazine ran some tests on this... for example, BP was claiming that their premium fuel would get you ~30 miles further per tank than normal unleaded; in reality, this turned out to be about 1.5 miles more for an extra £6.

[TeePee]

It all depends on the fuel.

Many fuels in the UK are now containing increasing amounts of Ethanol. Ethanol is bad. It's bad for your car, it's expensive to produce and it has less energy than real petrol, so your mpg goes down.

The oil companies love it, because they sell more fuel, and of course, being a 'naturla' product, it's good for the environment, right? Not with those increased emmisions it isn't!

Premium fuel often has less ethanol, and therefore would give better mpg. Horrifically, here in Oregon the gas has to have 10% by law, and this despite the price almost doubling in just over a year.

[Neo_VR]

Having just "upgraded" from my tuned Fabia vRS "scrabblewagon" to a tuned Octy vRS (new car thread to follow)

The irony is with the Octy being the bigger car, its still cheaper to fill up with V-Power than the Furby was with regular diesel. granted the tank wont go as far, but its more fun in the petrol.. The octy is mapped to run on Super unleaded anyway

[SilentDeath]

Keep meaning to test this - Does anyone know if a car will bennifit from it IF it can also still use normal 95 ron, if the timing is retarded by the ecu? (the owners book states 91+ octane is useable)

Not expecting more mpg ofcourse, since its more for performance...

I woul have expected the higher octane fuel to contain more ethanol since that is one way to get a higher octane...

[Zak33]

Super unleaded is normal petrol these days.

BP ultimate and Shell V-Power etc. raise the octane level and increase the detergent content, so they can help clean out older engines but won't really do anything for new cars.

gotta be careful on this Kal

Unleaded is 95 RON
"Super" was always 98 RON (and most Optimax / other top retail fuels)

4 star was around 97 RON

The confusion was because the continet often used alower octane rating (91RON) so we called ours PREMIUM UNLEADED ...note....this is NOT the same as SUPER>

Premium is normal
Super is better

If the car has cylinder by cylinder knock sensing (most modern cars do) it will readjust for every beat of it's litte heart, so putting Opti or similar high octane in will give slightly more HP and therfore you can use a tad less throttle and get slightly better MPG from it.

But it's hard to judge cost vs MPG. Most cars "feel" better on Optimax or similar because it is more responsive to the throttle, mainly because the ignition remaps itself to hold off the detionation a fraction longer to allow a higher compression which gives a better bang and more torque.

But many lower spec cars won't auto adjust so you waste your money on the better fuel.

[Zak33]

Keep meaning to test this - Does anyone know if a car will bennifit from it IF it can also still use normal 95 ron, if the timing is retarded by the ecu? (the owners book states 91+ octane is useable)

ya see....91 octane is for the continent but we never had it here.

[kalniel]

gotta be careful on this Kal

Unleaded is 95 RON
"Super" was always 98 RON (and most Optimax / other top retail fuels)

4 star was around 97 RON

The confusion was because the continet often used alower octane rating (91RON) so we called ours PREMIUM UNLEADED ...note....this is NOT the same as SUPER>

Premium is normal
Super is better

Ah that's the one My petrol brain has gone to mush since switching to an oil burner obviously

[Zak33]

np dude....I still get confused on these words....dunno WHY we use them.

Premium meaning normal is just....marketing hype. But it's what we have

[Lucio]

As someone who drives an older car (beat up L reg Mondeo), I defiantely get better performance out of my car if I use the Super rated fuel once in a while. Then again, you can also just chuck a bottle of Redex into the car once in a while too

[Barakka]

Someone told me once that SuperUnleaded was only worth using if you had a car with variable valve timing, but my old petrol 1.6 wasn't but definately performed better on it and got more miles per tank. It's a balancing act though, it gives more MPG, but costs more

I remember flling up at a petrol station in the US last year and it had a choice of three nozzles per pump which were labelled 89, 91, and 96 - obviously no diesel as that's just for trucks.

[Zak33]

Someone told me once that SuperUnleaded was only worth using if you had a car with variable valve timing, but my old petrol 1.6 wasn't but definately performed better on it and got more miles per tank. It's a balancing act though, it gives more MPG, but costs more

not valve timing.... ignition timing.

According to how high the Octane Rating (RON) is, depends upon how much the engine can "squeeze" the air&fuel mixture before igniting it with a spark.

Low Ron fuels have to detonate it a tad earlier, or it will detonate itself, very inneficiently , causing "pinking" which sounds like a loose set of marbles in the engine.

High Ron fuel can be left on the spark timing until a fraction later, allowing the air/fuel to be squeezed more before it gets set off with the spark plug and that little extra compression makes a huge difference to the power created.

Only certain cars can readjust to the better fuels automatially, but many many modern cars can do it automatically.

VALVE timing is something different. An engine often breathes better if the valves open and close for shorter durations at low revs, more in time with the cylinders movemet, and not to open too far either helps. (ie low lift, low duration)

But as revs rise, the engine literally breathes better if the valves open further AND for longer. Lots of modern cars offer this, VVT, VTEC, VVtI etc. lots ofnames for similar function. It akes the car more driveable and in theory, more ecoomial.

But it wont help with which fuel.... it just happens that many of those modern cars ALSO adjust with the fuel used anyway.