It’s no surprise that the engineering behind the latest turbo diesel engines comes from Germany. Gone are the days of excessive noise and gutless power delivery, diesel engines of today are proven to be more efficient and in many cases, more powerful than their petrol equivalents. The diesel revolution has begun.

A clear sign of diesel technological advancements is found in the Audi R10 TDi Race Car that was unveiled in December 2005. This car went on to win the infamous 2006 24 Hours Le Mans Race. The success of diesel cars in endurance racing can be partly contributed to their remarkable fuel efficiency enabling the car to make fewer pit stops.

In comparison, petrol engines run on average at about 30 percent efficiency, where as diesel engines run at over 45 percent efficiency. This is based on fuel energy being converted to mechanical energy inside the engine, making the diesel the most efficient of any regular internal combustion engine! The race winnning Audi R10 was powered by a twin turbo aluminium 5.5L V12 diesel engine, utilising Turbocharged Direct Injection (TDi) common rail technology and was rumoured to produce up to 700hp (522 kW) and 1200Nm of torque. The fact that such high performance could be achieved with a diesel engine undoubtably changed the way that the world looked at diesel cars.

Back in 2005/6 the campaign of the R10 was Audi’s way of being ultra-competitive at Le Mans while making a huge statement about TDi. A more recent, and notable addition to the Volkswagen family is the performance diesel Golf GTD TDi, offering 350Nm of torque at 1.750 rpm! Simply put, ‘torque’ is the pulling power of a diesel, combined with specific gearing to capitalise on the narrow rev range, this model Golf accelerates 0-100KM in 8.1 seconds. Utilising a version of the same ‘TDi’ technology seen in the AUDI R10, the Golf delivers an impressive 125kW. To put this pulling power into perspective the NEW 3.0L Commodore deliver’s 290Nm of torque, so considering the Golf uses an average of only 5.5L/100km of fuel and is wrapped up in a GTi handling package, you can see the appeal.

As TDi technology in diesel engines becomes common, specific products are manufactured to cater for their unique characteristics. When it comes to TDi engines Liqui-Moly offers both fuel and oil additives to suit and most importantly the Volkswagen certified engine oil – the Liqui-Moly ‘Top Tec 4200 5W-30’ (specification VW 507.00), which covers the new Volkswagen GTD.

When the oil light comes on in a near new car it’s normal to ask why? In most cases the oil just needs a top up, which poses some important questions… What’s considered to be ‘normal’ oil consumption? And what are the factors that influence consumption?

Before we explore why oil consumption occurs, it should be noted  that a level of consumption should be anticipated in all engines. This is a common fact that is communicated by the car manufacturers themselves, and published in owner’s manual.

As an example a 2008 VW GTi owners hand book explains that “It is normal for the engine to consume a certain amount of oil. Depending on how you drive and the condition in which the car is used, oil consumption can be up to 1.0L/1,000km”, so topping up small amounts between services is considered acceptable and should really be expected.

ENGINE DESIGN
Engine oil consumption can depend on a number of factors, typically late model more advanced technology engines run at hotter temperatures to increase engine efficiency and reduce fuel consumption & emissions, high operating temperatures often cause an increase in oil evaporation loss and an increase in oil consumption. Combine a high operating temperature with a low viscosity oil (which most engines are now being spec’d with) like a 5W-30 or 5W-40, and it’s inevitable that oil will escape past moving parts and sealing rings at a higher rate. Design and operating scenarios aside, the following engine problems can also cause oil to disappear at a high rate:

• Defective or clogged PCV (positive crank case ventilation)
• Bearing & general engine wear
• Cooling system problems/engine hot spots
• External Oil leaks
• Engine sludge and clogged oil galleries
• Cylinder Glazing
• Over filling
• Incorrect oil

These are all things that can be diagnosed by a dealership when under warranty or a specialist repair workshop.

IS IT OK TO BE 1LITRE LOW?
The average car takes between 5-6 litres of oil, when the oil needs to be topped up by 1 litre (a volume that makes up a significant percentage of the overall oil capacity) it’s definitely NOT ideal. Regular checks of the dipstick is the best way to keep an eye on the oil level and is far better than seeing the oil light come on. Thankfully you can rest assured that the car manufacturers have engineered the oil capacity to adequately cover normal consumption and the warning level. A guide to what the oil level should be on the dipstick for all cars is published in the owner’s manual.

TOPPING UP
When topping up the correct specification or approved oil is needed, using the Golf GTi as an example, it requires the VW 502.00 approval, which is carried on numerous Liqui-Moly products like the Top Tec 4100 5W-40 or the Liechtlauf Special LL 5W-30 , both are available in top up sizes of 1L. Keeping a 1L spare on the garage shelf or in the boot could come in handy if you ever get caught out. Check out the Liqui-Moly online oil guide to find the correct oil for your car.