Selling your classic car? It's FREE to list your car on Honest John Classics | No thanks

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

Answered by Alan Ross
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
Similar questions
I am buying a 1972 Renault 4TL. Do I need to use a fuel additive with this motor?
I'm now coming across contradictory information regarding the use of E10 fuel in classic car engines. I was under the impression that it was a big no no due to the higher ethanol content absorbing water...
My 1970 Jaguar 420G has been on a SORN for a number of years. The restoration is nearly complete. How do I get it registered and back on the road?
Related models
Enormous, with room from three on the front bench seat alone. Still looks and feels like a Jaguar, despite how big it is.

Compare classic car insurance quotes and buy online. A friendly service offering access to a range of policies and benefits.

Get a quote