Sludge, The Engine Killer!

Toyota has it, so do Ford and Volkswagen. As do Dodge and Saab. The chances are, if you drive a modern car in stop-start traffic, you may be getting it some time real soon. The ‘it’ is engine sludge, a killer of engines, in much the same way that arterial sclerosis will stop your heart. To put it simply, to your car, the formation of sludge is an engine killer and we all know that the engine is its heart. If your engine develops sludge, you could be looking at a four or even five-figure repair bill.

The Centre for Auto Safety, a consumer advocacy group in the USA, has received over 3000 complaints about sludge problems in recent years. A large majority concerns the base 2.7-liter V6 used in the Dodge Intrepid and a relative handful involved engines used in the Audi A4 and VW Passat, but this may be because the VW Group agreed to pay maintenance costs for all 479 000 of the 1.8-litre turbo engines affected. Potentially the most infamous of them was the Toyota class action suit in the USA which they finally settled with an advocacy group in 2007. The case involved an estimated 2.5 million Toyota and Lexus vehicles made between 1997 and 2002. Toyota agreed to repair the sludged engines for up to eight years from the date of purchase. While Toyota staunchly maintained that any such ‘oil-gel’ problems are attributable to owners’ abuse or poor maintenance habits, the automaker did set up a mechanism to reimburse complainants. The language of the settlement appears to include reimbursement to owners who have already paid to have their sludge damage repaired. The problem was so acute that it made USA national news on frequent occasions:

But why stop at this one video? If you are bored one afternoon, just Google the name of just about any car manufacturers’ name you know – Dodge, Chrysler, Ford, Honda, etc – with the additional ‘sludge problems’ keywords. You will see page after page about the subject. The obvious question is why does this problem persist and why don’t the auto manufacturers do something about it?

Most of the automakers claim that the problem is the customers’ bad maintenance habit – not changing the engine oil at the correct interval, every 7500 miles (12 000 kilometres) or six months, whichever comes first; Toyota USA added the caveat ‘under normal driving conditions’ and if you drive your car ‘under severe conditions’, then the oil should be changed every 5000 miles (8000 kilometres). So, what are ‘normal driving conditions’? What is the cause of engine sludge and how can ensure that we don’t ‘catch it’?

Engineers and engine builders mostly agree that the primary cause for sludge is what is known as ‘blow-by’. This occurs when small amounts of combustion gases cross from the combustion chamber into the oil in the form of ash; often this is acidic and it is primarily why most oils are formulated to contain some alkaline in the form of calcium or magnesium, that is designed to keep these byproducts of combustion in suspension until your next oil change. There are other causes of sludge, including not operating the vehicle at the correct temperature (either too hot or too cold) or water contamination. The most likely culprit in the formation of sludge, though, is driving in stop-start conditions, much like taxis, delivery vans and even the average commuter car do. The ASTM D6593 oil sludge resistance test involves replicating town driving conditions to observe if the test oil will inhibit the formation of sludge.

The real problem comes when you have a modern engine, particularly turbocharged engines as SAAB famously found out in the eighties, that operate at a higher temperature coupled with drivers that do not drive under ‘normal conditions’. In the USA, normal driving is defined as an average speed of 72kph when the reality is that the average driver drives at speeds between 30 and 50kph. In big cities such as London or New York, the average speed drops to just 20kph. What this means to the average city driver is that your service interval has just halved; in other words, your engine oil has ‘worn out’ before you get to the service interval, and will be unable to protect your engine and stop the build-up of sludge. This is how Toyota and all the other manufacturers define ‘severe driving conditions’.

Many manufacturers have been acutely aware about the cost of maintenance and have pushed the limit on service intervals with many recommending service interval of 10 000 kilometres to even 15 000 kilometres, which in some conditions could prove fatal to your engine. The problem of sludge becomes worse with every oil change. Under normal operating conditions, the sludge is held in suspension by magnesium or calcium that is part of the detergency package in most modern oils. When the oil has ‘failed’ and sludge is being deposited, the sludge is not discharged with the oil when you drain it. This persists through every oil change until the engine becomes clogged and fails.

So, how do you avoid engine-killing sludge? Well, firstly you need to understand the type of driving you do; if you drive mostly in the city with stop-start traffic, then chances are that you are stressing your engine and depleting your oil a lot faster than you think. Of course, you should always follow the manufacturer’s recommended oil change schedule, but if you are a town driver then, to be safe, you should check the life left in your engine oil every week, also called oil trending. Most drivers would not know how to do this but there are cheap DIY test kits, the most famous of which is supplied by Fluid RX.

Many mechanics will also recommend flushing your engine on an annual basis with one of the non-kerosene flushing agents that are available in the market, such as X-1R Engine Flush, which is a non-caustic cleaner. Of course, always use the best oil that you can afford but ensure that this oil is the same weight as the manufacturer’s recommendation, and you could always give it a better chance by adding a good quality engine treatment, such as X-1R Engine Treatment, a product that is proven to extend the life of your oil by reducing metal-to-metal friction in your engine.


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