Your Engine Oil: Check, Don't 'Clean'

Engine oil is the lifeblood of your vehicle, lubricating moving parts, reducing friction, and helping to keep the engine cool. Ensuring your oil is at the correct level and in good condition is a fundamental aspect of vehicle maintenance. While the process of a full engine oil and filter change is typically carried out by professional mechanics, understanding the basics of checking your oil and what happens to it after it’s been used is vital for any car owner. Far from being a simple fluid, used engine oil holds a complex chemistry and a fascinating journey from your sump to re-processing facilities, a journey that home attempts at 'cleaning' simply cannot replicate.

Checking Your Engine Oil: A Simple, Effective Method

Regularly checking your engine oil level is a quick and essential task that can prevent significant engine damage. The process is straightforward: locate your dipstick, pull it out, wipe it clean, reinsert it fully, and then pull it out again to check the oil level against the 'min' and 'max' marks. But what should you use to wipe that dipstick clean?

For decades, mechanics and car enthusiasts alike have debated the best material for wiping a dipstick. Surprisingly, a common household item often proves to be perfectly adequate: the humble paper towel. Many experienced individuals, with over 50 years of hands-on experience, attest that a paper towel will not fall apart when checking oil and poses no risk to your engine. The paper fibres are benign and will not cause harm. What you absolutely should avoid, however, are traditional shop rags. These can sometimes leave behind lint or threads that could potentially contaminate your oil or block small passages, leading to unforeseen issues. The simplicity and effectiveness of a paper towel make it a reliable choice for this routine check.

The Futility of Home Oil Filtering: A Detailed Experiment

The idea of re-filtering old motor oil to make it reusable might seem appealing, especially given its origins in the ground and subsequent refinement. After all, if oil can be refined once, why not again at home? This intriguing concept has led many to experiment, often with disappointing results. One such experiment involved attempting to clean dirty engine oil using common household items like paper towelling and even rope, drawing inspiration from historical methods and folk wisdom.

Attempting Filtration with Paper Towelling

The first approach involved creating a small test filter from a tightly rolled piece of paper towelling, inserted into the cut-off bottom of an empty oil bottle. Dirty oil was then poured through. The immediate result was clear: the oil passed through, but remained distinctly dark. While the paper towelling did show a slight gradient, with one side appearing darker, suggesting some particulate capture, the oil was far from clean enough to be considered reusable in a vehicle. It barely seemed to have changed in appearance.

A second, more ambitious attempt involved stuffing rolled paper into a prescription pill bottle to create a tighter column filter. This trial, unfortunately, suffered from leakage, rendering it a failure in terms of practical filtration. Upon inspection, the filter again displayed a gradient, but the oil throughout remained largely dirty. The expectation of a significantly lighter oil colour at one end of the gradient was simply not met. The hypothesis that larger particles would adhere to the paper while cleaner oil flowed through proved incorrect. The particles in used oil, such as burnt oil, burnt petrol residues, and microscopic metal shavings, are often the same size as or even smaller than oil molecules, allowing them to pass through rudimentary paper filters.

The Rope Filter Siphon Experiment

Another fascinating, albeit equally unsuccessful, method explored was the 'rope filter siphon.' Inspired by capillary action, a piece of clothesline was set up with one end in used oil and the other leading into an empty bottle. The rope itself was discovered to have a paper core wrapped in cotton yarns, which seemed promising for capillary action. However, after a week, most of the cotton remained surprisingly non-oily, indicating that capillary action was insufficient for significant oil transfer. The paper core did become completely soaked and stiff, suggesting it had absorbed oil and swollen, but the volume of oil collected in the clean bottle was negligible. If it produced even a few ounces in a week, processing a full gallon would take an entire year. The conclusion was unequivocal: neither paper filters nor rope can effectively recycle or clean used engine oil for reuse.

Why Home Re-Filtration Fails: The Complex Nature of Used Oil

The failure of these home experiments lies in a fundamental misunderstanding of what constitutes 'dirty' used engine oil. It's not just oil with some large particles floating in it. Used oil is a complex mixture containing:

• Original oil base stock
• Burnt or oxidised oil molecules (polymers or radicals)
• Burnt petrol residues
• Minute bits of scraped-off metal from engine wear
• Other foreign objects that may have entered the system
• Detergent additives that have broken down or become saturated

The process of oil oxidation, where hydrocarbons burn, is not simple. It can result in both larger molecules (polymers) or smaller ones (radicals). While used oil tends to thin out rather than thicken in the engine, indicating less polymerisation, it still contains a vast array of contaminants, many of which are molecularly integrated or too small for simple mechanical filtration. Professional refining requires sophisticated processes to separate these components effectively.

The Essential Role of Proper Used Oil Recycling

Since cleaning used oil at home is ineffective, the next logical step is proper disposal. Discarding used engine oil improperly, by leaving it out in leaky jugs or pouring it down drains, is incredibly harmful to the environment. It can contaminate soil and water supplies, posing significant health risks and ecological damage. This is why proper recycling is not just recommended, but crucial.

Thankfully, disposing of used motor oil responsibly is easy and often free. Most auto repair shops and parts stores will accept used oil for recycling. These establishments often collect the oil in large barrels, which are then picked up by professional oil recyclers. These recyclers sometimes even pay shops for the used oil, highlighting its value as a resource.

What Happens to Recycled Oil?

Once collected, used motor oil can follow a couple of paths:

1. Burning for Heat: In some regions, used oil is burned as a fuel source for industrial furnaces or heating systems. While this might sound environmentally concerning, it's often done in highly controlled, high-temperature furnaces that minimise emissions, making it significantly 'cleaner' than burning coal, for example.
2. Re-Refining: This is generally considered the most environmentally beneficial option, as it reuses the oil as a lubricant rather than simply burning it.

The Science of Re-Refining Used Engine Oil

Re-refining used motor oil is a sophisticated industrial process that breathes new life into a valuable resource. It's a testament to engineering and environmental responsibility.

What is Oil Refining?

To understand re-refining, it's helpful to first grasp the basics of crude oil refining. In principle, crude oil refining is simple: oil is heated and then introduced into a large, vertical metal chamber known as a distillation column. Lighter hydrocarbon molecules rise to the top, while heavier ones fall to the bottom, much like how salad dressing separates over time. Different 'fractions' are then drawn off at various levels and further refined. The lightest fractions become fuels like petrol and mineral spirits, along with natural gases. Heavier fractions become lubricants, tars, and base materials for plastics. It's worth noting that traditional refineries, while essential, can have significant environmental impacts on surrounding communities due to emissions.

Re-Refining: A Sustainable Approach

Re-refining takes this concept and applies it to used engine oil. Instead of starting with crude oil from the ground, re-refiners begin with the used oil collected from workshops and recycling centres. This used oil is filtered to remove larger contaminants and then subjected to a similar heating and distillation process in a column. Different weights of oil are separated and then further purified. The end product is often a base oil that is chemically indistinguishable from virgin base oil and can be used to formulate new lubricants.

While re-refining is energy-intensive, requiring significant energy for collection and processing, it is inherently cleaner and more sustainable than drilling for and processing new crude oil. It reduces the need for new extraction, prevents pollution from improper disposal, and conserves a finite resource. It's a critical component of a circular economy for lubricants, transforming what was once considered waste into a valuable product.

The Economics of Used Oil as a Resource

The value of used engine oil is often underestimated. Globally, it's a commodity with a market price. For example, reports indicate that a tonne of used engine oil can fetch between $100 to $400. Even bottled, it can be priced around $2 a litre, which, while cheaper than new oil, still signifies its inherent value. The existence of mini-refineries, priced from £15,000 up to £500,000, suggests a viable business model for those who process large volumes of oil, highlighting that used oil is indeed a resource, not merely a waste product.

Re-refining facilities are strategically located, often near ports or industrial areas, to facilitate the collection of used oil and the distribution of re-refined products. While specific locations in the UK are not detailed here, such facilities exist to serve the national need for sustainable oil management.

Home Filtering vs. Professional Re-Refining: A Comparison

Frequently Asked Questions About Engine Oil and Recycling

Can I use a paper towel to check my engine oil?

Yes, absolutely. Based on extensive experience, paper towels are perfectly fine for wiping your dipstick when checking engine oil. They don't typically fall apart and the paper fibres will not cause any harm to your engine. It's a simple, effective, and readily available solution.

Should I avoid using shop rags to check my oil?

It's generally advised to avoid using shop rags. While convenient, some rags can leave behind lint or small threads. These fibres could potentially contaminate your engine oil, which is something you want to avoid to maintain engine health and prevent blockages in critical oil passages.

Can I filter my old engine oil at home to reuse it?

No, unfortunately, you cannot effectively filter or clean old engine oil at home for reuse. Experiments using paper towels, toilet paper, or even rope have shown that these methods are ineffective at removing the microscopic contaminants, burnt oil, and other chemical byproducts that accumulate in used oil. Reusing such oil in your engine would be detrimental.

What is 'burnt oil' in my used engine oil?

'Burnt oil' refers to oil molecules that have undergone oxidation due to high temperatures and pressure within the engine. This process can create both larger molecules (polymers) or smaller, unstable molecules (radicals). These altered molecules, along with other contaminants like metal particles and fuel residues, make used oil unsuitable for continued lubrication without professional re-refining.

Where should I dispose of my used engine oil?

You should always take your used engine oil to a designated recycling point. This typically includes most auto repair shops, vehicle service centres, or parts stores. They have facilities to collect and store used oil safely, which is then picked up by professional oil recyclers. Never pour used oil down drains or dispose of it in household waste, as it is a severe environmental pollutant.

Is re-refining used oil environmentally friendly?

Yes, re-refining used oil is considered a highly environmentally friendly practice. It reduces the need to drill for new crude oil, conserves natural resources, and prevents the pollution that would occur from improper disposal. While the process itself requires energy, the overall environmental benefit of reusing an already refined product significantly outweighs the impact of creating new oil from crude.

In conclusion, while the full process of an engine oil and filter change is best left to professionals, understanding the characteristics of engine oil, the proper way to check its level, and the vital importance of recycling used oil empowers every car owner. Your used engine oil is not just waste; it's a valuable resource that, through industrial re-refining, can be given a new lease on life, contributing to a more sustainable automotive future.

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