What fuel should I put in a 1964 Holden EH?

It’s nice to see that some of us are still recycling and keeping old cars on the road. Your question was a hot topic back in the mid-1980s when unleaded petrol (ULP) was being mandated for all new cars. The issue was that older car engines were designed to run on fuel with a small amount of lead in it to help protect (mainly) the valve seats (hence, leaded petrol). The lead also helped prevent detonation inside the engine by raising the petrol’s octane rating. Without this lead, the engine could wear out prematurely, and it was something that owners of existing cars were very worried about.

The ultimate solution for older engine was the installation of what’s called hardened valve seats which, as the name suggests are valve seats in the cylinder head that were physically harder and would cope with the lack of lead. Since your car is older than most people reading this, you may find that it’s on its second, third or even fourth engine and, in that time, may have been fitted with hardened valve seats. Knowing the history of the engine would be very helpful.

But if you don’t have that information, the best advice is to run it on 95-octane fuel (for the octane rating to prevent detonation) as well as a lead-replacement additive to protect the valve seats. This additive can be added to the tank when you fill up, or as a permanent kit fitted under the bonnet that drips a small amount of additive into the engine as it runs. The Valve-Saver brand was a popular make of this type of kit back in the day.

When the time comes to perform work on the cylinder head, think about having the valve seats replaced with hardened ones, at which point you can forget about the lead-replacement additive.