THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

Name The Fuel

My car was imported from England. What fuel did they have in England at that time and what was recommended for my car? What I am getting at is that I plan on using Premium Fuel. Do I need to add a lead additive to the fuel?

Thanks,

Back in the day the UK had 3 star cheap fuel. Four star was normal fuel and five star which was premium fuel All of them had lead.

In the UK now we have 95 Octane which is the normal fuel and a 98 Octane almost equivalent to the old five star both unleaded.
I use the premium 98 Octane fuel in my S type as I have found the cheaper fuel makes the car run on after switching off and with the amount of miles I do the price difference is insignificant.

As for leaded addictives all Jaguar XK engines have aluminum heads and as such have hardened valve seats fitted from the factory. Cast Iron heads where not fitted with valve seats and you used to grind the valve seat in to the cast iron head. Cast iron was softer than the hardened valve seats and the lead was added to to the fuel to lubricate the cast iron valve seats. Unleaded does not affect the valves themselves as these are already hardened.

It does make me laugh when I see a Jaguar up for sale and they state in the advert that the engine has been rebuild at great cost and Hardened valve seats have been fitted as if it did not have them before. So the XK engine has always been able to run on unleaded with no damage caused and do not waste your money asking for hardened valve seats to be fitted as you already have them.

Glyn will no doubt be able to give you more details on the different types of fuel and which is the best to use.

Valve seat recession issue. Lead was added to fuel as an octane booster with the secondary purpose of lubrication of valves & seats. Some people have even harder valve seats fitted for unleaded gas. All indications are that the standard Jaguar valve seat is more than tough enough for use with unleaded gas so don't even worry about it. I run standard seats with unleaded gas.

I don't know what pistons you have fitted. Come in 7, 8 & 9 to 1 CR.



I'm sure you have either 8 or 9 to 1 CR pistons & that your cylinder head has been shaved. Most heads today have been shaved.

Just run on the highest octane (AKI in the US) unleaded gas available for the region/altitude you live in/at. XK engines can be prone to knock (pinking, pinging, pre ignition, detonation by whatever name you know it)

Joe your engine number originally was 7B57313-8. The last 8 signifies you had 8:1 compression pistons fitted so unless you have changed the engine or had some major work done to it you should still be running these pistons.

You guys are a wealth of information....yes, mine is 8:1 compression with /8 after my engine number. Premium it is.
Thanks,
Joe

I'm sure your head will have been skimmed at some time pushing up the CR & making knock more likely ~ Premium it is!

Anyone have or know where I can get the Dip Stick Bracket for my car. SNG says not available. If none available, can someone send a good photo of one with a ruler next to it so I can make one?

Thanks,,,,

I will make a phone call for you Joe. Rob Burston should have one but I will get back to you.

Rob,
Any word from Rob, Rob? LOL

Sorry Joe I forgot will phone him tomorrow for you. I have put a note in the diary.