Super unleaded or not?

[A900ss]

I have a funny feeling I might be opening a can of worms here but I thought I'd ask....

The label by the fuel cap says Super unleaded only (or words to that effect).

I have two thoughts on this

1 the design of the engine is ancient so why does it need super unleaded

2 the ignition may be set for super therefore regular unleaded may cause knock/detonation which I don't really want as I like my pistons.

Any thoughts/comments most welcome.

[Alun450]

My simple rule is unleaded for slow, super for fast! It's definatly faster and smoother running with super but mine runs fine on both really. Someone will confirm the facts soon I'm sure.

[Bassfiend229hp]

There are two things that when discussed are guaranteed to start a war on here...

...religion and whether to use Unleaded / Super Unleaded / Ultimate Unleaded.

[QBee]

Alun450 said:

My simple rule is unleaded for slow, super for fast! It's definatly faster and smoother running with super but mine runs fine on both really. Someone will confirm the facts soon I'm sure.

Rob (V8 Developments) built me a well tuned/matched/sorted 5 litre engine and said unleaded for roads, super for track days. It runs fine on the cooking petrol. I had always used Super before. Honestly cannot tell the difference, so I agree with Alun.

[pac1uk]

My standard 400 I run normal unleaded now, couldn't tell any difference between super and normal. Tested at the same speeds and same roads.

I think if you have done engine mods e.g. running higher compression ratio, ignition timing changes then using super unleaded should be better due to higher octane rating and would stop pre detonation or knocking.

[QBee]

I only come on Pistonheads for the knocking.....

[A900ss]

Bassfiend229hp said:

There are two things that when discussed are guaranteed to start a war on here...

...religion and whether to use Unleaded / Super Unleaded / Ultimate Unleaded.

Sorry....

[A900ss]

pac1uk said:

My standard 400 I run normal unleaded now, couldn't tell any difference between super and normal. Tested at the same speeds and same roads.

I think if you have done engine mods e.g. running higher compression ratio, ignition timing changes then using super unleaded should be better due to higher octane rating and would stop pre detonation or knocking.

My car is big standard except for cam so regular should be fine then.

[StarmistBlue400]

Owned mine since sept and the last two tanks have been standard unleaded. Haven't noticed any difference performance wise but I think the pops are quieter.

[Bassfiend229hp]

A900ss said:

My car is big standard except for cam so regular should be fine then.

Absolutely ...

[Alun450]

I suppose the question is at slow speeds would you even get Knock and detonation etc with 95 Ron. Super just gives a more eager feel, and def fires cleaner through my engine.
I'd dispute if my engine gave much better fuel econ figures on super though!

[pac1uk]

For standard unleaded I use Asda pee grade unleaded, can't tell any difference with other brands of normal unleaded

[QBee]

Alun450 said:

I suppose the question is ............. better fuel econ figures ...............!

My other car's a TVR......what's fuel economy?

[Bassfiend229hp]

QBee said:

Alun450 said:

I suppose the question is ............. better fuel econ figures ...............!

My other car's a TVR......what's fuel economy?

My last car was an RX-8 - 76,000 miles in 3 years at 17mpg average ... after that the Tiv is positively frugal.

[Alun450]

Good answer. It has exhausts the size of a boys leg!! It's not designed to be economic! It's freaky fast though!

[jojackson4]

15-18mpg on gravy (QBee)

[Sardonicus]

QBee said:

Rob (V8 Developments) built me a well tuned/matched/sorted 5 litre engine and said unleaded for roads, super for track days. It runs fine on the cooking petrol. I had always used Super before. Honestly cannot tell the difference, so I agree with Alun.

That's about it nuff said

[locodude]

Just done 1200 miles around Scotland and Super unleaded was hard to come by so it got regular for a few fill ups and I honestly couldn't tell the difference. Oh and averaged 25mpg with no oil or water used.

[BountyHunter]

the engine/ecu isnt advanced enough to be able to switch the timing between different fuels - so it all depends on where the timing has been set to.

and thats the catch - in theory if the timing is set for SUL then running it on 95 could be problematic

a rr session could be advantageous - you could have the timing set to whatever fuel you desired that way

[Dr Mike Oxgreen]

BountyHunter said:

and thats the catch - in theory if the timing is set for SUL then running it on 95 could be problematic

Precisely. And you wouldn't necessarily know there was a problem. If your engine is starting to detonate, you won't notice any significant loss of power, and you won't necessarily be able to hear it.