Tech

Fluid for Thought – Keeping your fluids in check…

Oil good. No oil bad.

N2G contributor and Canadian, Jake Belder, has been getting all oily for you lovely people. Here, then, is his advice on how look after your car’s precious fluids…

One of the wonders of the human body is that your fluids clean and regenerate themselves. Take blood, for example. It flows through your kidneys, where it is cleaned, and the waste disposed of before it goes back to your heart. And should you do a good deed and give away some of your blood, your body will quickly generate new blood to replace it. That is all rather amazing, really.

Unfortunately, your car will not do the same thing. Donate some of your gearbox oil, and your gears will make haste to exit the casing. Fail to change your oil, and all the dirt it picks up inside your engine will accumulate into one big lump and turn said engine into a worthless chunk of metal. The fluids in your car are there to lubricate, clean, and protect the various moving parts, and they need a good deal of regular attention to ensure long intervals of happy N2G motoring. Let’s look at how to stay on top of each of the key fluids in your machine.

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Engine oil

No doubt when you think about fluids, the first one that comes to mind is engine oil. That is for good reason – it is the fluid you will replace most frequently. Oil, of course, lubricates the many moving parts inside your engine and prevents the metal-to-metal contact that will result in certain and probably catastrophic death of your motive power unit. It also helps keep the internals clean by gathering foreign contaminants and lodging them in the oil filter. While a lot of new cars can increasingly go up to 10,000 miles between changes, a good rule of thumb is to change the oil every 5000 miles or six months. Check your oil every week, ensuring it is at the right level. Clean oil has a nice golden hue; it gets blacker as it gets dirty.

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Gearbox oil

The other oil that is pressed into use in a high-stress environment is your gearbox oil. If you think about what goes on inside your gearbox, it might surprise you to know that a lot of manufacturers bill their gearbox oil as a ‘lifetime’ fluid, never in need of changing. That is nonsense, and all it really means is that the people who buy these cars new will probably trade them in before it comes time to service this oil. Like engine oil, gearbox oil lubricates all the moving parts inside the box and ensures smooth engagement of each gear. In an automatic gearbox, the fluid operates under pressure to change gear at the appropriate time, and means that must be kept at a precise level. You will find lots of discussion and debate online about how frequently to change the gearbox oil, but a good rule of thumb is every 50-70,000 miles. Manual gearboxes don’t tend to have a dipstick to check the fluid, but harder shifting is a good clue that it could use a change. Most automatic gearbox oil will have a bright red colour when it is clean. As it gets dirtier, you’ll find your gearbox a little less eager to respond. Use the smell test too – dirty automatic gearbox oil smells horrible, like something burnt. It is important to point out that automatic gearbox oil usually needs to be checked with the engine running and warm, and the gearbox in neutral.

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Brake fluid

Your braking system is hydraulic, using pressurised fluid to operate the calipers. Brake fluid is hygroscopic, which means it absorbs moisture over time, reducing its ability to flow properly (thus minimising the effect of the brakes), and becoming dirty as it picks up contaminants inside the lines. If left for too long, it will even begin to corrode the inside of the brake pipes. Brake fluid should be changed every two years, or 20-30,000 miles. If your brakes are feeling spongy, it is worth attending to the fluid. Again, a visual check of the reservoir will help you too – clean brake fluid is the colour of pale ale and gets darker as it gets dirtier.

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Power steering fluid

Most cars that fall under the N2G umbrella will be equipped with hydraulic power steering, which means that fluid is used to lubricate the steering rack and assist its movement when the engine is running. Like brake fluid, power steering fluid is hygroscopic, absorbing moisture over time and picking up dirt and contamanents. A good clue that your power steering fluid is in need of attention is a distinct whine from your engine bay at idle and low rpm, which gets louder as you turn the steering wheel. Like brake fluid, changing the power steering fluid every two or three years, or 20-30,000 miles will serve you well. Different cars use different types of fluid for the power steering, whether it is actual power steering fluid, central hydraulic fluid, or automatic transmission fluid. They have different colours, but when they are clean, will be bright in colour. Whatever you find in the reservoir, if it is murky, it is probably time for a change.

Differential oil

If you have a rear- or all-wheel drive vehicle, you will also have gear oil inside your differentials. This is one that you generally can’t inspect, and usually won’t give any particularly clues that it is in need of changing, but if you think about it, it is another higher-stress environment. If you have a 4×4 and do a lot of off-roading, you will want to change it more frequently, but for normal road use in a rear-wheel drive vehicle, every 30,000 miles is a sufficient service interval.

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Coolant

Finally, your engine generates a lot of heat, and needs to be kept cool. The cooling system cycles fluid through the engine block, where it absorbs heat before being sent back into the radiator to be cooled before being pumped through again to collect more heat. Coolant gets dirty over time, which reduces its ability to cool properly, and because modern engines have much tighter tolerances, heat will destroy them quickly. Therefore, your coolant needs to be replaced regularly. There are a huge range of opinons on how often this should be done, but you will usually find the recommended replacement interval falling somewhere between 30-60,000 miles. Coolant comes in various colours, but is usually a very bright green, pink, or red, and cars generally have coolant reservoirs that make visual inspection easy. If it’s getting dull and murky, consider a coolant flush.

When it comes to replacing these different fluids, consult your owner’s manual for details about which fluid the manufacturer recommends for each application. You generally do not want to deviate from their suggestions; in some cases, using the wrong fluid could be ruinous. Ultimately, your vehicle’s fluids are vital to its life, and there are few more important things you can do for your car than to keep them all clean and topped up.

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