Sorry for the likely stupid question but I am trying to get a few of my late father’s cars running after he died two years ago. They are a 1958 jag mk1, 1962 Daimler 250 v8 and a 1975 jag xj coupe.

I would assume the fuel in them isn’t at its best, they were apparently running in the year or two before he died but I would like to top them up with some fresh fuel to rule it out.

Am I right in saying I should be using E5 petrol and then add a lead additive? Which is recommended please?

I’m in the UK

Many thanks for any help, I’m not too familiar with cars of this vintage.

 

Just use the highest octane petrol you can buy and Jaguars do not require lead additives. Their valve seats are more than hard enough & do not suffer recession on unleaded petrol.

 

Thanks so much, that’s great news. I know the v12 xjs that’s also in his collection refuses to like anything but E5 so I’ll get some more of that and give it a go. I just assumed I’d need additive for the older ones on top.

Great to know, thanks for your help. I have a hardi fuel pump on its way to me too from your recommendation in another threads. Thanks again.

 

How much fuel is in the tanks? If they are not full the fuel in them will be rotten & have lost all it's light ends. The old fuel should really be drained.

 

Thanks, between 1/4 and 1/2 full I think. I’ll get them drained to be on the safe side. Thanks for the tip.

 

Glyn has answered the question regarding fuel and mentioned that Jaguars of this era do not require leaded fuel or additives so I would just like to explain why. So many times in "For Sale" adverts for Jaguars you see the phrase added saying "Converted for use with unleaded fuel," generally meaning hardened valve seats have been fitted.

There were two types of material used to make cylinder heads in the 1960s. Cast iron was the first which is a soft material and the valves seats were cut directly into the cast iron so the hard material of the valve sat directly onto it. Lead was added to lubricate I assume with other reasons (Glyn can explain this better) between the cast iron and steel valve. Without the lead in the fuel the cast iron becomes pitted and you no longer have a decent seal therefore loosing compression and power.

Jaguar in its XK engine used an alloy head which being very soft required hardened steel valve seats pressed into the head. The steel valve was now sealing against the hardened steel valve seat and although lead was in the fuel it was not actually required in the XK engine so when lead was removed there was no need for any additives.

So if you ever see an advert saying a Jaguar with an XK engine has been converted to run on unleaded fuel by having hardened valve seats fitted the owner is either lying or he was ripped off by an unscrupulous garage which did and charged for work that was not required or didn't do anything but charged them anyway. That is not to say the valves seats can't be renewed but they would be the same material as the original ones.

 

The only additive that I've used in my cars was an octane improver on my Daimler V12. It was an early HE and I think a previous owner had skimmed the heads rather severely. It had a disturbing 'tinkle' when cruising on slight uphill slopes. The additive had a small effect. The replacement engine we put in about 20 years ago has never had a problem.

There's a lot of discussion about gasoline with ethanol separating, degrading and attracting water, but conventional gasoline degrades as well. We get as much gasoline as possible from of a barrel of oil (whitening the barrel) by mixing as much light components with as much heavy heavy ones as we can. Left in a tank, the light part evaporates first, other things degrade, there's probably condensation of water on the tank walls and corrosion. So yes, after a few years of standing, definitely drain the tanks and dispose of the contents. There are recommendations to use various additives if you don't use your car for a few months over the winter. Personally, I've never bothered. I keep my cars in my garage or workshop with dehumidifiers set low and very low level heating. I brim the tanks with a premium fuel, usually BP Ultimate, and have never had a problem. In fact, I always use premium gasoline as I'm convinced of the long term benefits.

Incidentally, the purpose of lead was to increase octane rating. Any wear reduction was a happy side effect. It disappeared because it poisoned exhaust catalysts. There was also some argument that we were poisoning ourselves and that it caused juvenile delinquency!

 

Between you & Peter you have done just fine. TEL & TML were added as octane boosters and valve seat protection was always taken into consideration for certain engines with no hardened seats (leading to valve seat recession) ~ at least by our Supermajor Oilco that I can speak for. With the XK engine valve seat recession would show itself by the engine becoming quieter as cam to bucket clearance closed up. This does not occur.