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Classic Cars and Modern Fuels.

Are They Compatible?

By Dr. Cathryn Hickeys
Technical Fuels Manager of Shell UK

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Public interest in air quality has increased; Nearly a third of all drivers questioned in a recent survey stated that they were very concerned about exhaust emissions. Advances in refinery technology have enabled some retailers like Shell to address these concerns through the introduction of modern fuels offering emission benefits.

However, from my discussions with motorists - including classic car owners - and motoring organisations I am aware that some drivers are confused about the benefits on offer while others are concerned that the new fuels can bring adverse side-effects. In particular, I believe that some enthusiasts are wondering whether modern fuels are compatible with classic cars - a view compounded by a mischievous leaflet recently distributed at the Birmingham NEC.

To help clarify matters and to see how Shell could help, I contacted club secretaries. Several recommended that Shell could address some of the questions and concerns raised by classic car owners most effectively by writing a short article for possible inclusion in club newsletters.

I am pleased to enclose an article which builds upon the contents of 'The Shell Fuel Guide for Classic Cars' published in the early 90's. It answers the most commonly asked questions about modern fuels: "Need adjustments be made to classic cars before using modern fuels?; Can classic car emissions be cut without affecting performance?; Do modern fuels offer the same power and engine protection qualities as traditional types?"

A pioneering spirit has long been associated with Shell. This is perhaps best demonstrated through our continued leadership in fuel development, not least our aim to offer a range of fuels offering emission and performance benefits to all vehicles - including classic cars. I hope the enclosed is of use to you and your members. Happy motoring in 1996.

Answers to questions from classic car enthusiasts

Technological innovation and society's desire for more environmentally friendly products has led to significant changes in fuel composition in the last ten years. Unleaded petrols were introduced in the 1980's, fuels containing detergent additives became widely available in the mid 90's and most recently Shell has introduced a low lead 4 Star.

Shell has long been credited as a pioneer of fuel quality, consistently leading the field by bringing new fuels to the marketplace. We firmly believe that the introduction of new fuels should be undertaken with care to ensure that a range of high quality fuels suitable for all types of vehicle is widely available. Due to its leading edge research programme, run in association with long established motor manufacturers, Shell has successfully introduced advanced fuel technology while offering motorists the peace of mind that it can safely be used in older vehicles as well the most modern. Some classic car enthusiasts, however, have posed questions about the suitability of modern fuels for their cars and from recent discussions I have detected that there is much confusion about petrol composition. I hope I can clarify matters by addressing those questions most frequently put to me.

What is petrol?

Petrol is a blend containing more than 300 different chemical compounds.

Does petrol quality vary?

Yes, because the composition of the chemicals which comprise petrol can vary widely. High quality petrol should have the right octane level to prevent knocking; strong cleaning power to prevent carbon build up, deliver more miles per gallon and ensure engine life is maximised; and the correct volatility to ensure vehicles accelerate smoothly and start first time.

Why is lead added to petrol?

Tetraethyl lead is added to 4 Star petrol to provide the necessary octane rating (anti-knock quality) and to act as a lubricating barrier between the exhaust valve and seat in cars with soft valve seats.

What is octane rating and how does it effect the running of a car?

The octane rating is a measure of a fuel's resistance to knocking. Knock, also known as 'pinking', occurs during combustion when the fuel-air mixture explodes ahead of the name front rather than burning smoothly, causing a knocking noise. Using a method established in 1929, petrol is rated on a scale of 0 -100, and given a research octane number (RON). In the 1920s petrol had an octane rating of around 50 to 60 RON. Today, 4 Star has a minimum octane rating of 97 RON.

Can classic cars run on today's petrols with higher octane ratings?

Yes. Using today's modern fuels with higher octane ratings won't harm the engines of classic cars designed to run on petrols with low octane ratings.

My car was designed to run on 2 Star petrol. Now that this isn't available which fuel should I use?

Classic cars were designed to run on the low octane petrols which were available earlier this century and therefore have a low octane requirement. Now that low octane 2 Star isn't available classic car owners should use the higher octane British Standard 4 Star, which is suitable for classic cars and won't harm engines. Shell Advanced Low Lead 4 Star is also a British Standard 4 Star.

My car runs 'hot' on modern fuels. Why?

Carburettors in classic cars were set up for the fuel quality of the time they were manufactured. Due to the progressive improvements in fuel quality over the years they may now need adjusting. If they aren't adjusted engines may run 'hot' because too much or too little fuel may be introduced into the combustion chamber.

Why is lubricating of soft valve seats important?

Without proper protection, exhaust valves can weld themselves to the soft seat, causing serious damage or engine failure. Lead is a highly effective protective lubricant. A lead level of 0.05 grammes per litre offers complete protection. The British Standard for leaded 4 Star (BS4040) requires a minimum lead content of 0.05 grarnmes per litre.

Why has the amount of lead in 4 Star been reduced over the past 30 years?

Until 1967 lead was blended at a concentration of one gramme per litre. However, growing concerns about the amount of lead entering the environment in the late 60's and 70's led to legislation which progressively reduced the maximum permitted concentration of lead in petrol. The last mandated change came into force on January 1, 1986 when the maximum level was cut from 0.4 to 0.15 grammes per litre. As lead content has been reduced, the amount of high octane hydrocarbons in the petrol blend has been increased to maintain the necessary octane rating. In the new Shell Advanced Low Lead 4 Star Shell has cut the amount of lead to 0.075 grammes per litre, a level which offers complete valve seat and engine protection, while enabling motorists to halve their lead emissions.

Will leaded 4 Star petrol be phased out or banned? If so, when?

Leaded petrol has been banned in some European countries but the UK Government hasn't indicated that it plans to do so here. The UK leaded petrol market currently accounts for about 37 per cent of total petrol sales, a percentage which is falling each year as new cars designed to run on unleaded enter the market. By the turn of the century less than 10 per cent of all cars in Britain will need leaded petrol and it may not be as widely available as it is today.

What will replace leaded petrol?

Lead could eventually be replaced by lead replacement additives. These are used in continental Europe, most notably Austria and Scandinavia, where leaded fuel has been phased out. In the UK, there is as yet no British Standard for petrols containing lead replacement additives and Shell believes this is necessary to ensure that these fuels offer vehicles in the UK the guaranteed level of protection. UK motor manufacturers still recommend leaded petrol for the millions of UK vehicles with soft valve seats which need lubrication.

What is Shell Advanced Low Lead 4 Star petrol?

New Shell Advanced Low Lead petrol is a breakthrough for 4 Star leaded drivers because it enables them to join unleaded drivers in cutting their emissions of lead to the air, while still having enough lead to protect their engines. It cuts lead from car exhausts by half and meets all the requirements of the British Standard for leaded 4 Star.

What's replaced the lead that Shell has taken out, to maintain power, performance and reliability?

Shell refineries vary the combination of high octane components in Low Lead 4 Star to give it the same octane rating - and same engine power and performance - with less lead. So it has enough lead for complete valve seat and engine protection, with no loss of power or performance.

What should classic car drivers do if they currently use the 'I in 4' system (1 fill of 4 Star for every for 3 of Super Unleaded)?

Instead of using this cycle of fills they should use Shell Advanced Low Lead 4 Star all the time. This will halve their lead emissions but still give them full engine protection.

What sort of tests has Shell done to ensure Low Lead won't damage classic car engines?

Shell has tested the product extensively at its Thornton Research Centre in Cheshire. In addition, independent experts and motor manufacturers have tested Shell Advanced Low Lead. These tests have shown that a minimum lead level of 0.05 grammes of lead per litre offers full valve seat protection. Shell Advanced Low Lead 4 Star typically contains 0.075 grammes of lead per litre, more than the minimum required. It is approved by all major motor manufacturers. The Vintage Sports Car Club and consumer groups including the AA and RAC have endorsed the manufacturers' view.

Will the performance of classic cars change when using Shell Advanced Low Lead 4 Star?

No. The octane level of Shell Advanced Low Lead 4 Star is guaranteed to be the same as traditional 4 Star - 97 RON. This means power, performance and fuel economy won't be affected in any way. The petrol is the same as traditional 4 Star except for the lead content and meets the British Standard for 4 Star.

Can you mix Shell Advanced Low Lead 4 Star with other 4 Star petrols?

Shell Advanced Low Lead 4 Star can be mixed with any 4 Star. However, to minimise lead emissions Shell Advanced Low Lead 4 Star should be used regularly.

Where can classic car enthusiasts buy Shell Advanced Low Lead 4 Star?

It is available at over 1,000 Shell service stations including many cities including London, Leeds, Newcastle, Chester, Manchester, Sheffield, Nottingham and Birmingham. customers can find out whether their local service station sells Shell Advanced Low Lead by popping in or calling Freephone to the Shell Customer Service Centre on 0800 - 010100.

What benefits do modern detergent fuels offer owners of classic cars?

Petrols containing detergents offer benefits to all cars, no matter how old. The unique Shell detergent not only keeps engines clean but also cleans up harmful carbon deposits from old and dirty engines. Compared with rival petrols Shell Advanced Petrols offer improved fuel economy, quicker acceleration and lower exhaust emissions. This has been demonstrated by 2.3 million miles of road tests on different makes and models of cars and 4,500 hours of laboratory bench tests. The new Shell Advanced Low Lead 4 Star contains the Shell detergent package too.

Is benzene injected into unleaded petrol to help replace the lead and boost fuel combustion?

This is a myth. Benzene is not added to petrol; it occurs naturally in crude oil and is formed during refining. The amounts reaching the air from car exhausts have been greatly exaggerated, and the concentrations in the UK air have been examined by experts and found to be - by a very long way - no threat to public health.

Is it wise to drain the petrol tank before a winter lay-up?

No, an empty tank is more susceptible to corrosion. Cars are best left with a little petrol in the tank, with the battery disconnected and the engine sprayed with lubricating oil. A dehumidifier can help prevent the formation of rust. Try and start the car at least once a month and take it for a short drive if the weather is fine.

Can classic cars be converted to run on unleaded petrol?

Some can and some can't. Popular classics such as MGBs, Jaguar E-types, Morris Minors and most Aston Martins can be converted. The mono block engine design of some vintage cars like Bugattis or Bentleys makes conversion practicably impossible. Owners of cars which cannot be converted can cut lead emissions by switching to Shell Advanced Low Lead 4 Star.

Why was unleaded petrol introduced?

Unleaded petrol was introduced in 1986 to help the Government objective of cutting lead emissions into the environment and to enable the use of three-way catalytic converters. These greatly cut other exhaust emissions but can't run on leaded petrol because lead poisons catalysts. 'Cats' eliminate some 90 per cent of gaseous exhaust emissions - including the three regulated emissions - carbon monoxide (hinders breathing and impairs co-ordination), nitrogen oxide (contributes to acid rain and ozone) and volatile organic compounds (contribute to ozone formation). All new petrol cars registered since the beginning of 1993 must be equipped with catalytic converters and can therefore only run on unleaded petrol.

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