Fuel mix: Leaded AND Unleaded

[beavy69]

I have recently heard that mixing the two can improve performance as they contain different ingrediants that raize the octane level therefore increasing the overall octane of the fuel.

Supposed to be benificial as too much of one particular octane enhancement substance can actually lower the level.

Thoughts?

The thread: Leaded or Unleaded???? seems to suggest that either fuel is OK to put in the car.

Anyone with a definate contraindication to that?

[Adam]

If you put leaded into a CAT equipped engine, you will kill the cat.

[Stuart]

plus the cost and availability of leaded means you might aswell buy proper octane booster.. lol

[Jack]

Assuming you're talking about LRP - as iirc legit leaded petrol has been banned from sale in the UK since 1/1/2000 thanks to the EU - its essentially just Super Unleaded with a couple of additives to sustain the valve seals. If all you're after is an upped MON/RON rating (which isn't really worthwhile in a N/A car), just use SUL as adding normal unleaded to that will lower the overall octane.

[dannyb]

LRP fuel is usually 97 octane, Standard unleaded is 95. Mix the two and get 96 octane?? Thats like drinking half coke and half diet coke, you destroy your teeth and it doesn't taste like coke! Use Super Unleaded, you won't see a improvement in performance, but SUL usually has some additives to clean carbon deposits (BP Ultimate, V-Power ect).

[garyc]

You can get leaded petrol and also Tetraethyl lead as a additive to blend to unleaded to make leaded petrol. I still think TEL is the best additive though. Unless you have upped the CR I wouldnt bother. The V-power claims sound good. Also BP are doing a 102 octane unleaded at a few garages but its well expensive.

[Jack]

I think the BP stuff is something like ?2.40+ a litre, and they limit how much you can have each time!

Although, unsurprisingly, they haven't published the MON rating for that, nor have Shell for VPower - which probably means its sh*te and you're just as better off using bog std 95RON or a SUL :roll:

[SRI crazy]

hey quick thought if u can get leaded or 4-star mix it wif super unleaded i heard that is supposed 2 giv gud performance but u hav 2 get the super on the same day it is delivered 2 the garage because it starts 2 die if u leave it 2 long

[Jack]

..Which is what the OP said :p

Petrol does "go off" but tbh at most busy petrol stations its never sat there long enough. Small, quiet, remote stations then yeah.

[bigbened]

best get down to asda price then

[beavy69]

I normally FILL up with norm unleaded and top up with the BP stuff. So I think I'll just stick to that.

Now and then I'll use a bottle of Lucas octane booster. It's supposed to be higher in octane than even the NOS racing formula and despite having a NA engine I definatly notice the difference. But its expensive stuff! Having said that it's worth it once in a while anyway as its like a good dandruff shampoo for engine run on - stops it for a while without constant use lol (not that I ever have dandruff lol )

[Stuart]

seriously unless you actually CHANGE the ign setting then your really not doing much bar burning money with these "fancy" fuels......

[craig green]

Some gas stations are licensed to sell Leaded petrol still. I have one near me, its for classic vehicles supposedly. Couple of my mates run R5 turbo's & they use a bit now & again + my Dad runs about 5 classic motorbikes so its ideal for him too.

Lead is a good lubricant for fuel pumps, so if I had an old carb'd SR or something I'd use Leaded occasionally to keep the pump internals nicely lubed. Might keep it going for a bit longer?

[Stuart]

isnt leaded something like ?1.00 a litre? (it was when i got some last time when normal petrol was 75p lol)

im sure the cost of gettign a new fuel pump is effectively cheaper per mile than running leaded through it now and again....

i think the baf far outweighs the "gains" lol

[jon boy]

stuart dont know **** ! I use bp ultimate and nitrox boost and it gives me nufffff horses yo ! like 35 or 40 !! ;)

[craig green]

OK Jonboy!

I dont run leaded myself Stu so only passing on info. But back in the day the lead was used to lubricate & old cars etc had fuel pumps dependant on being lubricated by the lead. Best to have a bit in there now & again than to have it pack up, surely?

Not really Nova related I know but worth knowing.

[Stuart]

i guess its worth a shot now and again... but obv a cat equipt car shouldnt use it at all lol.

when i bunged some 4* in a good long time ago in my std 1.2 it ran sooo damn hot lol, im actually surprised that since i hadnt changed the ign timing that an exhaust valve would have burnt out due to retarded burn time.

[Jack]

I'm sure my dad used to use some form of additive in his Dolomite with normal unleaded to give the same lubricating effects as the lead...

I've spent all day reading stuff about different petrols (any excuse to avoid work), tis all very interesting :D

[dannyb]

Bring back 5 star, a family friend used to use that in his RX3 in the 70s and it was around the 101 octane mark!! My dad uses std unleaded in the 1932 Standard 16hp, its such a little used, ineffcient lazy engine with a CR of about 5:1 that 95 unleaded is hardly likely to damage the valve seats.

[Jack]

Bring back 5 star, a family friend used to use that in his RX3 in the 70s and it was around the 101 octane mark!!
Wonder what the AKI or MON is on that though. Japan premium fuel is usually around 100+ octane. Although higher RON doesn't mean the fuel has more energy.

[Stuart]

exactly, ron is merely the fuels resistance to pre ignition... the calorific value is "usually" lower so if you dont change your ign settings it will lose you power and thermal efficiency from less engery transfer and also with a slower burn due to its ron "could" result in even more lost power as the peak cylinder pressue maybe pushed past the best point for torque... and keeping heat so late in the cycle can burn valves out.

but thats all theory and my personal views... which lets face it are cRaZy lmao

[Jack]

^ Thats pretty much summed up what I've learnt today :D

Also picked up some interesting info about Tesco 99RON; whilst the company who supply the fuel bang on about it having high RON/MON, they don't mention the calorific value. But they do say:


We also typically include 5% bioethanol ? a clean and pure ultra high-octane component which is also renewable to help cut greenhouse gas emissions.
They don't however mention that 5% ethanol is more than likely what raises the RON to 99; and also fail to mention adding ethanol lowers the calorific value of the fuel, so putting it in your average European car (tuned for either 95 or 97RON) which doesn't advance/retard the timing enough to make use of the higher octane could cause it to lose power.

Anywho, rambling and somewhat off topic now lol

[Stuart]

have to say my vx and an M3 i know of both respond better to tesco 99ron than on any other "fancy fuel", and when i say respond better they pic up revs better but power is about the same as usual...... i guess it ccould lead to better mpg, but as with all nice things you deck it more so its a vicious circle lmao