unleaded or leaded substitute petrol ?

[steve anning]

My crossflow ford 1700 has been converted to run on "Green" unleaded, I always put the leaded additive in when I fill up.

It crossed my mind that maybe I should be running the car on the "Red" leaded substitute petrol

What do you think Guy’s ?

 

 

 

[PeterS]

If the engine has been properly converted, there is no need for the additive. One of the reasons for wanting to retain the lead is because of valve seat recession. If your head has had the appropriate hardened inserts fitted, then surely you're ok. The other reason for the lead was as an anti-pinking admixture. If the car performs and sounds ok without the additive, why pollute the atmosphere?

I'm sure a proper brain will be along in a minute to give formal technical explanations.

[Simos]

The red has a higher octane rating than the green (nominally 97 vs 95) as it is basically superunleaded with a potassium additive to slow valve seat wear. (yes it is cheaper than the same unleaded stored in the same tank but without the potassium... that's taxation for you)

 

If you've got hardened valve seats then you can use either from a valve seat wear point of view.

However the lower octane rating of 95 vs the old 98 of leaded means that your ignition "may" need retarding to stop pinking (burning in the wrong place in the cycle because of different burn characteristics)

 

My engine has hardened seats but because of timing has to run on 97. Sure I could have it changed but that would rob a bit of power so I don't want to.

 

When you were unleaded-ed they should have told you if you can use green or not and whether they changed your valve seats, timing or ecu map.

 

If you're doing a track day or pulling lots of revs blatting I'd use red regardless of whether you can use green or not, otherwise - save the money.

 

Simon.

[Super_Rich_Bernie]

I was told that the Pottassium is generally undesirable (corrosive I believe) and that if the valve seats are OK running on Super Unleaded is a better option.

 

My 1600Vx Caterham seems quite happy on normal unleaded so it's not an issue now, but it was on the Lancia I owned until recently, which needed the extra octane.

 

The respected Lancia specialist I used suggested steering clear of Lead Replacement fuel altogether.

 

Just thought i'd add that conflicting advice...........

 

Jonathan

[Casbar]

I have a xflow that was converted to unleaded.

 

Since the engine re-build (forged pistons, 244 cam etc) to get more power and run the ignition futher advanced, I was advised to run on either Super or LRP.

 

I now run on LRP. This advice came from Roger King, who's advice I trust. Give Roger a call, he will advise you.

[Alex Wong1697456877]

I run my car on LRP for the octane rating and because it's cheaper than SUL. I suspect my new R500 filler neck will mean I have to use the SUL pump from now on though.

 

I've not heard (until now) that the additives are in anyway harmful.

 

Alex

[Simos]

I have not heard that the additives are in any way corrosive to an engine (more corrosive than very hot acidic combustion gases ?) in fact they are there to act as a protection for exactly that high temperature corrosion as was lead before it.

 

I have heard tell that mixing additives may be a bad idea as no-one knows what will happen to the mixture of metals at high temperature but I don't think any quantitive results have been produced. Common sense says it's not ideal though.

 

Potassium (and in fact any of the additives) will spell the end of your CAT though....

 

I use LRP for the octane and because it's cheaper than Super and more readily available.

 

For smaller stations with limited tanks and pumps they might have to make a choice of LRP or Super in which case 'cos they sell way more LRP than Super you'll find LRP pumps but no Super pump even though LRP IS Super with an additive !

 

For the record I mixed additives on my BD for the year around the phasing out of leaded before I had the headed unleadeded and Roger did not say my valves were in any way worn. I have heard similar stories on other soft seated engines so any scare stories of your valves imploding 50 miles into a tank of premium are simply that, scare stories.

[CHRIS CLARK]

Don't worry Alex. With you being unable to fit the cap the fuel will slop out what ever you use; ha ha.

 

That'll teach you to fit quality 'K' car parts to a bl%dy V/X powered machine!

[steve anning]

Thanks Guy's

 

From your comment I believe that:-

a) Having had a proper unleaded conversion done there are no advantages in adding any lead additives to the fuel

b) Better to run on Unleaded 97octain (for me with a Orange distributor cap)

 

Guy’s

This has put my mind at rest in the knowledge that my 1700 friend under the bonnet is getting the right feed,

Cheers

Have a Wonderful Christmas

Steve

 

 

 

[Jonathan Ratty]

It's worth pointing out that if you have an 'unleaded' x-flow, supplied by Caterham in the late 90s (e.g. sold with a Classic, like mine), it is 99% certain that the conversion to unleaded consists of changing the distributor only.

 

Although the engines were described as being 'unleaded' fuelled, no work had been done on the valve seats (this according to the factory). I use a lead substitute, but a head conversion will be done in the future.

 

Regards,

 

Jonathan

 

 

 

 

[Graham Sewell]

I guess that, like a lot of x-flow drivers, I am waiting for exhaust valve clearances to close up before I get remedial work done. This is almost certainly being delayed by the use of pukka 4* (when I can find it).

 

Cheers,

 

Graham