21 replies to this topic

[jameseddolls]

Hi there guys,

 

so will be topping up at the weekend and was wondering if it would be ok to put super unleaded in the car instead of the ordinary stuff. Would it make any gain to the engine at all, never used super unleaded in my life so was thinking of treating the mini to some premium fuel.

 

thanks

[imaparana]

yes it will be ok but you wont notice any difference I believe

[grck1]

I use super unleaded as I find my mini runs best!/happiest on it. I think this is because the octane rating of super unleaded is 99ron as opposed to 97ron for normal unleaded. The aseries engine was designed with leaded/4star petrol in mind which had a octane rating of 99ron I believe

[the.stroker]

The below taken from an internet source .
"United Kingdom: 'regular' gasoline has an octane rating of 95 RON, with 97 RON fuel being widely available as the Super Unleaded. Tesco and Shell both offer 99 RON fuel. "

[jameseddolls]

so tempting to just fill up a whole tank, even if it costs £35 odd quid. It deserves a treat and think the old fuel may be going a bit sour. Only drive it at the weekends and it hasn't been filled up since January.

[Mini 360]

I only ever run mine on super but I have tuned the carb to suit.  As a result, using 95ron in an emergency to get me home wehre there arent any super unleaded stations around, it runs rough.

[Dusky]

Lots of it is in the mind. ;) Octane wont influence anything unless youre pinging. BUT
It greatly depends what brand you buy too, some brands have more ethanol in their fuel for example. Toghether with some other "impurities" this causes bad running. Super fuels tend to be a better blend.

Edited by Dusky, 07 March 2016 - 05:08 PM.

[Icey]

I only ever run mine on super but I have tuned the carb to suit.  As a result, using 95ron in an emergency to get me home wehre there arent any super unleaded stations around, it runs rough.

 

It's really ignition timing which needs adjusting to make the most from higher RON fuel, playing with the carb isn't going to achieve much. If you see rough running on 95 vs 97 I'd be looking for other reasons (unless you're running boost or high compression, then it would make some sense).

 

One of the biggest differences I've seen with 'premium' fuel is extended viability. It seems that 97 or 99 RON fuels keep better. One reason I've been given is the difference in ethanol content but I've yet to really look into it so really just anecdotal at the moment.

[dklawson]

+1 to Dusky's and Icey's comments.

[jameseddolls]

_{thanks guys this is very helpful. Loving all the replies, the mini forum is brilliant especially for us new comers to the mini world like myself}

[Blatherskite]

I only ever run mine on super but I have tuned the carb to suit.  As a result, using 95ron in an emergency to get me home wehre there arent any super unleaded stations around, it runs rough.

 
It's really ignition timing which needs adjusting to make the most from higher RON fuel, playing with the carb isn't going to achieve much. If you see rough running on 95 vs 97 I'd be looking for other reasons (unless you're running boost or high compression, then it would make some sense).
 
One of the biggest differences I've seen with 'premium' fuel is extended viability. It seems that 97 or 99 RON fuels keep better. One reason I've been given is the difference in ethanol content but I've yet to really look into it so really just anecdotal at the moment.

SWMBO used to work in fuel distribution. The ethanol evaporates and/or attracts water, both of which takes it out of the petrol. The petrol is off-spec until the ethanol is added, result being poor petrol and bad running for sensitive vehicles. Different marques have different ethanol content; until recently, Esso was ethanol-free in Norway, for example.

Our ex Army Series 3 landy was specified to be able to run on Russian 77-octane petrol, and has the markings to reset the timing to do so. Guess the same applies to minis and de-ethanolled petrol.

Edited by Blatherskite, 07 March 2016 - 05:30 PM.

[DannyTip]

As above really. It seems to last better in my mini which gets used infrequently.

[lapider]

To run a car on Premium fuel (anything over 95 octane) and see good results you need the compression ratio to match. The higher the octane the less likely the fuel is to be prematurely burned by engine heat. The higher the compression the hotter the engine gets. Also I think old leaded fuel used lead to act as a coolent and prevent the heat of the engine effecting ignition timing.

I've also remember reading somewhere that the octane rating isn't the be all and end all. The ethanol rating is also important. Eg tesco momentum has the same octaine rating as shell v power. But shell has a lot less ethanol. If I remember correctly.

Basically if your running a high compression. Highly tuned or forced induction engine it will make difference to power. If your engine isn't highly tuned it will probably make it slightly more responsive and slightly smoother. But for best results you want your carb turned to match the fuel.

Also on a side note I believe there is a difference between winter fuel and summer fuel. Also modern petrol with all the additives can "go off" quicker than petrol of old. This shouldn't effect minis as much as modern cars with plastic fuel injection components. Basically what I'm saying is if you drive the car 10 miles every other weekend your probably better off trying to top up a little when you need it.

Edited by lapider, 07 March 2016 - 07:06 PM.

[Anthony30]

I always use Shell v power in mine.  

[Orange-Phantom]

Ethanol in modern fuel is the biggest problem us classic car owners face, super unleaded is a better quality fuel, has a higher octane rating (which means less pinking) and is less likely to contain the hydroscopic ethanol.

 

I would always use super unleaded in a mini, even if it wasn't a highly tuned engine like I've got due to the extra benefits it has and it's only a few pence a litre more.

 

I'd also love to know about carb tuning for a specific fuel and how that works!  If someone can point me to some actual evidence I'd love to read it!

 

Tetraethyllead was added to fuel to raise it's octane rating, it is an Antiknock agent and it acts as a buffer against microwelds forming between the hot exhaust valves and their seats.