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Do I need an E5 additive for my classic Daimler?
I am fortunate to have and look after a 1969 Daimler Sovereign (420). I am having to use E5 fuel and would appreciate your guidance on which additive(s) would help protect the Jaguar XK engine? I believe lead replacement is less of an issue with this engine but I am concerned about the adverse effects of the ethanol content of E5 petrol.
Asked on 4 August 2023 by Patrick Begley
![](http://images.honestjohn.co.uk/imagecache/file/pad/120x120/media/15217131/alan_polaroid.jpg)
All XK engines can run happily on unleaded fuel (with no additives) because their alloy heads had to be fitted with hardened valve seats. However Jaguar specified 5 star petrol because of the 9:1 compression ratio so I suggest you use Super Unleaded wherever possible - Shell V-Power, BP Ultimate or Total Excellium. It's a small price premium but given you are unlikely to be using the car as a daily driver it will be money well spent with no pinking and a more spirited performance
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