Classic CarsInteresting News and Tips

What type of fuel can be used with vintage cars?

By in Classic Cars, Interesting News and Tips

Leaded fuel was withdrawn from Australia in 2000 because of concerns about lead pollution to the general population. But many older, classic and vintage vehicles are designed to run on leaded fuel. So what should you do if you’re thinking of buying a classic car? We look at some solutions to the problem.

What Did Leaded Petrol do for vintage cars?

The lead compound added to leaded petrol was cheap, and it was an easy way to raise the octane rating on fuel which older cars’ engines need to run. Specialist high-performance cars need 100-octane fuels, but they could get by on 97-octane leaded and even Lead Replacement Petrol (LRP) which, until it was phased out, contained other metal compounds such as potassium. The other thing that lead did was protect the engines valves and valve seats from wear and tear.

 

What Can Unleaded Petrol do to Vintage Cars?

But for vintage and high-performance cars to run on 95-octane unleaded would just cause trouble. Unleaded fuel contains around 10% which is ‘hygroscopic’, which means it easily absorbs water. Water leads to condensation in fuel tanks, fuel lines and carburetor fuel bowls. This can cause water contamination and fuel phase separation (when the ethanol separates from the petrol). This makes it a lower octane fuel than it was, and bad news for your car’s engine. Ethanol is also highly corrosive, forming rust wherever air meets metal once it’s submerged in it.

Although some pre-1986 vehicles are capable of operating on unleaded fuel, if yours isn’t, what options do you have?

 

Can I Modify My Vintage Car’s Engine?

Yes, in theory it’s possible to modify a vintage car’s engine to run on unleaded fuel. But it’s quite costly and involves a major engine overhaul. This can involve replacing valves that are made from wear resistant materials that won’t corrode when in contact with unleaded fuel.

Alternatively, if you don’t want the expense of an engine overhaul, you can use a lead additive for old cars. Normally the protection for your engine afforded by these additives is perfectly satisfactory. The general rule of thumb is to get the dosage correct and to stick with one brand. Suitable additives are those that are phosphorus, sodium, potassium or manganese based.

You could also see how your car performs on unleaded petrol in a sensible way, for example not driving it long distances. With moderation and checking for loss of compression or reduced valve clearances, it may be fine.

 

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