The risk of ethanol in fuel for classic cars

Modern fuels contain more and more ethanol. This is a big concern for classic car owners, as these fuels are not suitable for older fuel systems. In our workshop, we get to work on many cars with fuel related problems. Most of these can be tracked down to old petrol, especially in relation to a high ethanol content.

Pictured above is the top part of a Weber carburettor from an MGB. The car was parked for several years, causing severe contamination in the fuel tank and carburettor. This eventually led to clogged up needles and a leaking brass float. Luckily, replacement parts are easily available and relatively affordable. It just takes an awful lot of time to get everything working like it should...

After several months, ethanol starts to attract moisture. This will eventually lead to corrosion in your fuel tank and pipes. Old fuel evaporates into a gooey substance, clogging carburettors and injectors. The ethanol is also aggressive to certain materials used in classic car fuel systems, such as rubber, cork, copper and brass.

How to prevent these problems? Here are some tips:

  • Use petrol with the highest available octane grade (preferably 98 or higher, if available). These fuels contain less ethanol.
  • Use your classic car regularly, at least enough to refuel every 6 months.
  • Pay attention to your fuel hoses. Are they ethanol resistant? If in doubt, replace them with high quality modern rubber.
  • Replace your fuel filter regularly.
  • When storing your car long term, fill it up with high grade fuel. Try to let it run every other month and store it in low-humidity conditions.  

Want to dive deeper into this subject? Read our previous posts on classic car fuel and storage tips.


What petrol to use in a classic car?

Which petrol should I use in my classic car? Customers regularly ask us for advise on the best fuel for their classic car. Because the answer is longer than the question, we wanted to share this information with other classic car enthusiasts.

Many older gasoline engines have been developed to run on leaded petrol with a high octane content. Fortunately (for environmental reasons and public health) this fuel is no longer available. Classic car owners should therefore look for alternatives. In this post we treat the most common fuels: Euro 95, Super 98 and E10 gasoline. We also deal with the use of lead replacements, high octane petrol and driving on LPG.


Euro 95 or Super 98?

As a rule of thumb, engines with higher compression need a higher octane gasoline than engines with lower compression. The higher the octane content, the lower the chance of pinging or detonation. Pinging is the spontaneous ignition of the air-fuel mixture, beyond the time of ignition. This creates opposing forces in the combustion chamber, which translate into an irregular course and a beating or pounding sound. That this is not good for the engine may be clear; It can cause serious engine damage.

The choice for Euro 95 or Super 98 is open for discussion. Many classic british cars run well on 95, provided the ignition is well adjusted. Generally, this should be somewhat later for E95, so that no spontaneous combustion occurs (too close to the top dead center). Especially for engines with a little lower compression, Euro 95 is perfectly suitable. This includes sedans, but also sports cars that were delivered to the American market in the 1970s with a somewhat lower compression (MGB, TR6). The sportier driver will benefit more from the highest possible octane content. Tuned engines with faster camshafts run better and last longer with 98.


E10 gasoline (ethanol)

For many classic cars, ordinary Euro 95 is more than sufficient. It is important however, to ensure that not too much ethanol has been added. For example, E10 gasoline (with 10% ethanol) is absolutely out of the question. Many soft parts in the fuel system (rubber hoses, diaphragms in fuel pump or carburettor, cork, zinc) are affected. Also, old petrol residue can dissolve in E10, resulting in concentration of pollution elsewhere. Also, ethanol (a type of alcohol) attracts water. This can lead to moisture and thus corrosion in the tank, especially during a longer period of storage. For example, Euro 95 often contains 5% ethanol. Therefore, if your classic is not used for a while, it is advisable to refuel a premium gasoline with the lowest possible alcohol content (Super 98, V-Power, Excellium, etc.).

(many types of wear parts for the fuel system of Triumph and MG sports cars can be ordered in our webshop)

Some suppliers are offering additives for E10, specially designed to counteract the harmful effects on our classics. We have no experience with these products and cannot say what the long-term effects are.

Lead substitute

Adding a lead substitute only makes sense if the cylinder head has not yet been rebuilt to unleaded specification. The lead substitute ensures protection of softer valve seats. Without the additive, they will wear faster, which can lead to compression and power loss. We supply a Castrol lead substitute, available in our webshop.


High octane petrol

Some filling stations in Germany offer 102 grade petrol. In the Netherlands, this grade is offered by Firestone, under the brand name Competition 102. Although for most cars the benefits will be hard to notice, it is good to know that no ethanol has been added to this high octane petrol.



Personally, I think gas is great for cooking, but I would never want it in my car. Typically, our classics are not driven enough to compensate for the higher costs of installation and maintenance. In addition, I'm an originality freak that does not like to drill holes where they do not belong. Treat your car with respect and leave the LPG installation out.


Always store with a full tank

This prevents condensation and rust on the inside of the tank. Is the car being stored for a long time? Keep in mind that the average Euro 95 petrol is outdated after about 6 months. In that case, it is better to refuel a premium petrol. After prolonged storage, always check the petrol hoses under the car and in the engine compartment and replace the fuel filter regularly.