Lead Replacement Petrol (LRP)

Which cars must use LRP and why?

As well as boosting fuel octane, lead acts as a lubricant between the contact surfaces of the exhaust valves and the valve seats in the cylinder head. Certain older vehicle engines (pre mid-eighties) were made with soft metal valve seats as they were protected by the lead in the petrol. If all metal additives are removed from petrol, the soft metal valve seats may become worn and valve seat recession (VSR) may result in loss of compression and power. The most critical operating conditions for VSR are high speed and/or high load and these lead to high valve temperatures and hence greater wear rates.

The vehicle compatibility database which is widely available, including on the NAAMSA and SAPIA websites, clearly indicates which older vehicles, susceptible to VSR, should use a Lead Replacement Petrol (LRP). The oil companies either market LRP through the pumps on their forecourts or else provide a bottled additive which can be purchased and added in measured quantities to the vehicle's tank when filling up with unleaded petrol.

To accommodate motorists whose cars cannot use unleaded petrol, Engen will make a lead replacement petrol available at our service stations. Engen has decided to use a manganese additive (MMT) in our blended LRP as we consider this to be the most effective additive for this purpose. Not only does it provide adequate protection against VSR, it also enables the blending of the most environmentally friendly petrol for use in vehicles that have not been fitted with catalytic converters.

What bottled additives should I use?

There are a number of anti-wear additives on the market that will protect your car's valve seats in the same way as LRP. Additives with either potassium, phosphorus or manganese as active ingredients will provide adequate protection if dosed correctly in accordance with the manufacturers' recommendations.

Does using an anti-valve seat recession additive, in addition to using LRP, provide better protection for my engine?

No. You should use either an AVSR additive or LRP. Some additives may be unsuitable for mixing with LRP.

What are the consequences of using lead replacement petrol (LRP) if my car is fitted with a catalytic converter?

LRP should not be used in cars fitted with catalytic converters, because certain of the additives used may adversely affect the catalyst. For that reason LRP isl only sold through larger diameter nozzles which do not fit the filler pipes of vehicles requiring unleaded petrol.

When was it be compulsory for cars to be fitted with catalytic converters?

As from February 2005, all new petrol-powered passenger and light commercial vehicle models introduced in South Africa need to meet mandatory maximum emission levels and hence should have been fitted with catalytic converters. As from January 2008, all new petrol-powered vehicles of all types, whether they are new or existing models, must be fitted with catalytic converters. There is no requirement for cars built before these dates to be retrofitted with catalytic converters. In excess of 70% of all new cars are already fitted with catalytic converters.

How do I use suitable bottled anti-valve seat recession (AVSR) additives?

Anti-valve seat recession additives are very easy to use. Simply inject or pour the required amount of additive into the fuel tank prior to filling up with unleaded petrol. These additives provide valve seat recession protection similar to the protection that was provided by lead in leaded petrol.

How do I know that anti-valve seat recession additives will protect my engine?

Anti-valve seat recession additives can substitute for lead replacement petrol quite satisfactorily provided that you choose an additive from a reputable manufacturer that is specifically designed to protect valve seats and you use it exactly as instructed on the packaging. Be aware that protection is needed most when the vehicle is operated under high engine speed or load conditions, such as during extended periods of highway driving whilst towing a heavy trailer.

Does using more of an anti-valve seat recession additive than the recommended amount provide better protection for my engine?

No. You should not use more than the recommended amount of additive.

Does using an anti-valve seat recession additive, in addition to using LRP, provide better protection for my engine?

No. You should use either an AVSR additive or LRP. Some additives may be unsuitable for mixing with LRP. Different additives could also be incompatible with each other and so it is advisable to stick to one.

If my car currently uses ULP, will using LRP or an AVSR additive provide it with additional protection?

No. Continue to use your usual grade of ULP as your car does not need the protection that LRP or AVSR additives provide. If your car is fitted with a catalytic converter, using LRP or AVSR additives could damage the catalyst. You must use only ULP as recommended in the vehicle's handbook.

What increase in octane can I expect when using Valvemaster Plus?

Engen market Valvemaster Plus as an Anti Valve Seat Recession (AVSR) agent, not as an octane booster. However, the use of Valvemaster Plus in unleaded petrol is likely to result in a limited increase in octane. It must be noted that this additive is unsuitable for use in vehicles equipped with catalytic converters.

The NAAMSA vehicle compatibility database recommends that I retard the timing on my vehicle. Is this necessary and who does this work?

If you were using 95 octane unleaded petrol in the past this will not be necessary, just continue using 95 octane unleaded petrol. If you were using 97 octane leaded petrol contact your vehicle supplier to confirm whether or not it is necessary to adjust the engine timing to prevent engine damage. Contact details for the major vehicle manufacturers can be found on http://www.naamsa.co.za/unleaded/contact.php.

What increase in octane can I expect when using Valvemaster Plus?

Engen market Valvemaster Plus as an Anti Valve Seat Recession (AVSR) agent, not as an octane booster. However, the use of Valvemaster Plus in unleaded petrol is likely to result in a limited increase in octane. It must be noted that this additive is unsuitable for use in vehicles equipped with catalytic converters.