Major advances in oil technology have enabled Volkswagen to introduce a variable servicing option on most models. VW says that most petrol models can be driven for 19,000 miles or 24 months without a major service. Some diesel engine models can reach 30,000 miles or 24 months.

Engine sensors electronically monitor the vehicle's oil temperature, oil pressure, oil level and brake pad wear. A dashboard display informs the driver when a service is due.

The extended service intervals, while good for customers and the environment, will hit dealer profits, particularly on the sale of oil.

Oil companies have consequently launched a number of summer incentives, many aimed specifically at increasing customer awareness about the benefits of using more profitable synthetics.

Texaco is linking its promotion of Havoline Synthetic with the chance to win a luxury villa holiday.

Ray Tighe, Texaco manager of automotive products, said: “Our dealings with aftersales managers, dealer principals and certain manufacturers highlight the growing need for workshops to stock synthetic oil alongside other products.

“Warranty oil specifications from certain manufacturers, particularly the German and some French, may not stipulate a synthetic specifically, but close reading of the technical data leaves the workshop with little choice.

“Market research carried out over the past five years also shows that there is a core customer base that demands synthetic engine oils,” he added.

Mr Tighe predicts that dealers will be able to make an increased premium on engine oil sales by stocking synthetics.

“As it's Texaco's policy to allow dealers to set their own price, it is difficult to be precise about profit margins,” he said.

“However, looking at comparative product prices for synthetics we estimate that selling a synthetic oil attracts a premium of £8 per service fill and £4 on top-up sales of one-litre packs.

“Dealers taking up the promotion could make an extra £800.” The Texaco promotion includes two 205-litre barrels and seven cases of 12x1-litre top-up packs, enough for 80 major services.

Total, part of the TotalFinaElf group, is promoting its new Quartz range, designed to meet the needs of 95% of the Volkswagen Group's diesel and petrol engines, including the turbo diesel launched in the UK last year.

Total Quartz 505.01 is a synthetic-based, 5W-40 multigrade oil. The synthetic technology used in the formulation gives the product the properties of both a fluid oil for easy cold starts and a viscous oil for low consumption and lubrication at high temperatures.

With the introduction of extended 20,000-mile service intervals on many VW Group models from 2001, lubricants for these vehicles will be required to meet VW 503.00/506.00 standards. For these instances, Total has developed Quartz 9000 to cover the most stringent requirements of both diesel and petrol engines with extended oil change intervals.

Simon Westlake, marketing manager for Total Lubricants UK, said: “The changes in engine design, emissions regulations and increases in performance and service intervals are forcing engine manufacturers and oil companies to work together to ensure that the required goals can be achieved.

“The demands on a modern engine are phenomenal and lubricants must now be considered as engineered components in just the same way as pistons, valves and injectors.

“Lubricant development has to run hand in hand with advances in engine technology for there to be any progress, but at the same time there is a desire to keep things as simple as possible when it comes to vehicle servicing. Nobody wants to have to stock a separate product for each engine variant with all the problems and potential risks that involves.”