6 Flushing and beyond
Many experienced Diyers are sceptical about lengthy fluid drain intervals and ‘sealed for life’ claims. Rightly so, says Rob Marshall, who looks at the options available to the knowledgeable car owner.
Longer service intervals and sealed-for-life claims will send a shiver up many a DIY mechanic. Can flushing help cleanse mechanical components?
Are extended service intervals genuinely useful for the reduction of running costs, or a means of storing up expensive problems for a future owner? As the majority of new cars in the UK are bought by businesses, reduced workshop visits remain an important sales factor. Marketing departments, therefore, have been keen to react, not always with the full blessing of engineers, and maintenance schedules have increased gradually over the decades. 3000-mile intervals were common in the 1970s, increasing to around 10,000 for most cars during the 1980s. By the mid2000s, even certain diesels were sold with 20,000-mile service intervals. Intriguingly, this figure has tended not to increase since then. In some cases, it has even been reduced.
Subjective life-spans
As attention to the various fluids tends to be the most time-consuming part of a typical routine maintenance schedule, it is unsurprising that many lubricants have been formulated to stay in place for as long as possible.
Long-life, ultra long-life, extended life and similar phrases can be confusing, when no time, or mileage, drain interval is specified. ‘Sealed for life’ might be seen as an absolute statement but even its meaning can be subjective. ZF, the respected designer and manufacturer of automatic gearboxes, told us: “ZF automatic transmissions are generally filled with lifetime oil. However, due to the many factors influencing the service life of transmissions in individual operation, ZF recommends an oil change after 150,000km (approx. 90,000 miles) for its transmissions. In operating conditions, with high temperatures and loads, or with unknown vehicle use in the past, it can make sense to change the transmission oil at shorter intervals.”
We also queried one motor manufacturer about its definition of ‘sealed for life’; seven years was the response – a figure that, co-incidentally, represents the average car’s age in the UK. As many CM readers own cars in good condition that are far older than this, their definition of ‘life’ will be rather different.
The influence on emissions
Should you own a car aged more than seven years, with a mileage in excess of 70,000 miles, you may wish to consider treating it to a 'super service', which involves not only replenishing the fluids but also flushing through any deposits that might have accumulated. These contaminations tend to be carried by the fluids but, ultimately, they can fall out of suspension. They result not from a manufacturing defect, however, because
the deposits build-up naturally as the vehicle is used. The rate at which they do so depends greatly on driving style and conditions, as well as the overall design of the engine.
Deteriorated fluid and contamination build-up can affect efficient operation, which can raise exhaust emissions sufficiently to cause an MOT fail. This has been especially true since the revised tailpipe emissions standards for modern diesels prioritise the specification stated on the vehicle plate (which varies according to make and model) rather than a set figure. Depending on the components, flushing additives can be used that assist with dislodging contamination. The fluid then holds it in suspension and is drained-out soon afterwards, prior to the system being replenished with new fluid/filter. Should no additive be available, flushing with fresh fluid can also have positive benefits.
The following steps detail what a DIYER might wish to perform at home, including an overview of available products. Should you wish to engage a garage to carry out a professional flush that might be beyond what is achievable by a home mechanic, we also provide an overview of those operations, too.
Engine oil
Apart from its critical cooling and lubrication roles, engine oil has to neutralise the harmful acids of combustion and hold any contaminants in suspension, until it is drained. A consequence of using ethanol/bio-diesel fuels, and adding various technologies to reduce tailpipe emissions, is that modern direct-injection petrol (GDI) and diesel engines make their oil work harder and for longer. Reduced sump capacity in some engines does not help, either. They are also more sensitive to contamination, which results when their oil reaches a saturation point and deposits the various by-products of combustion around the engine. Sludging that can be seen at the coolest point of the engine, such as beneath the rocker cover, is the most obvious sign.
Naturally, prevention is better than cure, and it is well-established that engines benefit from regular oil and filter changes. Should you buy a used car with patchy service history, or even an example where the official but overly lengthy service interval has been followed (which can be biennial in some cases), it is certain that a degree of sludge, soot and varnish would have built-up within the engine that is neither immediately obvious, nor desirable.
For both the professional garage and the keen DIYER, a range of pour-in engine oil flushes are available that help to clean as much contamination from within the engine as possible.
Gilbert Groot, from the Dutch JLM Lubricants, told us his personal and professional view on the topic:
“It is strongly recommended to flush out old oil before putting the new oil in. You will drain a lot more deposits and dirt to allow the new oil to perform much better, because its characteristics will not be affected, or affected less. It is a simple and low-cost procedure with very positive effect, especially longer term. It should be an integral part of an oil change as you will condition your engine. I really think it is a missed opportunity to keep your car in check, when you don’t do it.”
Whichever flush you choose, follow the instructions carefully; some of them permit you to drive the vehicle; others contain more solvents than others and demand that the engine is run without load.
BG Products told CM that its oil flush “is designed to clean the deposits that form behind the piston rings. These deposits inhibit the proper function of the rings, leading to relatively early loss of compression and the ability of the rings to stop the oil vapour from coming up into the combustion chamber (this also adds ash to the particulate filter). Given that good compression helps to fulfil efficient combustion on a diesel (and GDI), and that oil vapour is detrimental to DPFS, then this product is a vital part of performance, economy and DPF maintenance.”
Klarius concurs that, while its engine flush additive is also designed to clean piston rings, it not only contains antifriction additives to protect the engine components during flushing but also, being a professional-use product, is formulated using ingredients in higher concentrations than those found in a typical off-the-shelf product for the consumer market.
Dave Norton, Technical Services Manager of Wynn’s UK, adds that the philosophy of the Wynn’s brand is focussed on quality and rigorous research and development of the formula. “We spend a long time and considerable sums ensuring that our engine flushes are safe for engines and effective for the user. We are aware that there is a race to the bottom in terms of price, but we prefer to uphold a high technical standard. This can be seen beyond the contents of our Engine Flush; our products are sealed and sold in child-proof containers where required; we even have a child-proof ring-pull on our metal cans.”
Beyond engine oil flushing
Naturally, pour-in engine flushes have their limits. Mr Norton advises that, where severe contamination is found within an engine, a degree of dismantling and physical cleaning will be necessary. Looking beyond what is possible for a DIYER, EDT Automotive offers an interesting alternative, offered via a network of garages across the UK.
By heating a light soy-based mineral oil and pumping it into and around the engine’s oil galleries for approximately 12 minutes, the company claims that up to half a litre of harmful ‘cholesterol’
residue is removed, prior to it being vacuumed from the engine sump. Since CM looked into the EDT Engine Deep Clean treatment in 2015, the treatment has been enhanced. The warmed mineral oil now flows through a 1 micron filter, as opposed to the earlier 5 micron type, and the operations are carried out four times in a single treatment, instead of three, to address the issue of newer engines being more vulnerable to contamination.
As EDT claims up to 26% improved economy and reduced smoke emissions by as much as 61%, we tried an unscientific experiment on the author’s 2006 Citroën 2.0-litre HDI diesel. Since it was three years-old, the recorded MOT fastpass smoke opacity readings averaged approximately 1.2m-1. These reading were taken consistently every year shortly following a full service, including an oil change. After the EDT treatment, it was noticed that, while the fresh oil looked cleaner than in previous post-service checks after several minutes of engine running, it had returned to its usual black hue after around 60 miles of driving. Nevertheless, a week and 500 miles later, the car was submitted for its MOT test, where the fast pass smoke opacity recorded 0.9m-1 indicating a decrease of 25%. While our blunt comparison would not stand up to laboratory-type levels of accuracy, it indicates that the treatment has made a difference. No subjective improvement in power or fuel consumption has been noted, however.
Added extras: oil supplements
After the work is completed, replenish the sump with the recommended grade, specification and quantity of oil. You might wish to add an oil conditioner afterwards, especially if your model has a drain plug positioned above the base of the sump. Certain Vauxhalls, for example, have their plugs located approximately 30mm from the sump bottom, meaning that up to 15% of the old oil is left in-situ, ready to contaminate and reduce the new lubricant’s service life.
David Wright of the independent organisation, the Verification of Lubrication Specifications, told us that
oil fortifiers are generalised products and, considering the increasing sophistication of modern engines, one type of engine oil cannot be expected to suit all vehicles, just as one type of oil fortifier cannot suit all engines.
LIQUI MOLY produces both engine lubricants and additives and, while it acknowledges that there is no set standard for additives, it insists that its additives are fully compatible with every common engine oil and cannot affect the oil’s chemistry negatively.
Wynn’s told us that its Super Charge conditioner is fully compatible with modern lubricants, has a low SAPS formulation (i.e. particulate filter safe), complements the oil and supports the engine's lubrication system.
Lucas Oil highlights that its Complete Engine Treatment fortifies the oil, reducing gum and varnish effects, while improving cold temperature fluidity and enhancing friction and wear protection.