It’s the life-blood of your engine, but it frequently gets overlooked. We investigate the ins and outs of your car’s oil.
It’s obvious that oil plays a fundamental part in the longevity of your engine. Without it your engine would last a matter of minutes, so it’s fair to say that it plays a vital part in order for your engine to stay healthy.
The moving components inside your engine all rely on a constant supply of oil in order for them to function, with a thin film of oil between the moving parts providing the necessary lubrication for your car to go on for thousands of miles.
It’s clever stuff, but it’s worth taking some time to appreciate the different types of oil, what the numbers mean plus the extra thought you need to spare if you’re planning to take your car on track. Read on to find out just how important oil systems are…
TYPES OF OIL
You may have heard people talk about synthetic, semi-synthetic and mineral oils. To add even more confusion to all the numbers, there are different types of oil available for your car, all of which possess different characteristics.
Mineral oils were used back in the day when that was all that was available. As the name suggests, they’re made from naturally-occurring oils and as such, have a limited heat range. They’re great for older cars in which the seals can be damaged by the use of more modern synthetic oils, though.
Semi-synthetic oils are just that – they’re made up of part synthetic and part mineral oil, so offer a sort of hybrid option. In order to be semi-synthetic the oil needs to be less than 30% synthetic, but that portion of synthetic means that a wider range of heat grades are available over mineral oils.
Synthetic oils are actually seldom made up of 100% synthetic, and instead in order to receive that status they simply have to be made up of more than 30% synthetic. These types of oil are man made and modern, and as such offer improved protection for your engine, longer service intervals and a wider choice of different grades. The downside is that they’re more expensive than the other types of oil.
HOW OFTEN SHOULD I CHANGE THE OIL?
This depends both on the car itself and the type of use it receives. If the car’s relatively standard and you don’t drive too hard, there’s no real reason to deviate from the manufacturer’s recommended oil change intervals, which typically are around every 10-12,000 miles. However, if the car’s higher performance, then the oil changes can be scheduled far more regularly. Even on stock Mitsubishi Evos the recommended oil change intervals are around every 4,000 miles due to the nature of the engine.
If your car is highly tuned or receives a lot of abuse on track or at the dragstrip, we’d recommend oil changes more regularly – every 1-2,000 miles. This may sound a pain in the arse, but it makes a lot of sense. The oil’s ability to protect your engine over time diminishes, so if you’ve got a £15k engine it would be silly not to look after it as well as you can.
WHAT DO THE NUMBERS MEAN?
You may notice oil containers have coding such as 10W40. It’s known as the SAE grade and the initial number is known as the ‘W’ number, which represents the viscosity (thickness) of the oil when at -25°C. The lower the number the thinner the oil, and for cold-start oil protection you’re looking for the lowest number you can. The majority of damage to engines occurs on start-up, so it’s important to have an oil that performs well from cold.
The second number represents the oil’s ‘hot’ viscosity, or how thick the oil is when it’s at 100°C. When the engine is hot you want the oil to be thicker than on start-up, and this is especially important in performance engines which will run hotter than a standard unit. The higher the second number the more suitable it is for engines that run hot, so bear this in mind too.
WHAT GRADE OF OIL IS SUITABLE FOR MY CAR?
It’s hard to argue against having an oil with a low ‘cold’ figure, which is the first number – 10 out of 10W40 for example. There’s never a time when you won’t want your car’s engine protected from cold starts, so 0W is ideal.
In regards to the second number, this is more important and again it depends on the type of engine and the usage. For relatively low-performing engines a ‘hot’ grade as low as 30 would often suffice. But if the car’s turbocharged or older, then a higher grade would be advisable – with 60 grade being the highest we’ve encountered. This is used in the realms of big-power turbocharged cars where the heat generated can be massive.
THE NEXT STAGE
Choosing the right type of oil for your car is all very well, but that’s not to say that’s as far as you need to go in terms of keeping your performance car healthy, especially if it gets used hard.
Track, race and drag cars have to withstand additional stresses and that has an affect on the oil. If you imagine a car cornering hard, the oil in the sump will act the same as if you’re trying to run whilst carrying a bucket of water. It doesn’t stay put, and instead will move around under cornering, acceleration and braking forces. This can have disastrous results – if the oil moves to the side of the sump, the pick-up pipe can’t supply oil to the rest of the engine. It’s known as oil starvation and it spells disaster, but there are ways around it.
WHAT IS AN OIL COOLER?
This is a common upgrade that’s fitted to a range of regular performance cars, and is highly advisable if you drive the car hard or it’s tuned. In a similar way that the car’s radiator keeps the water cool, an oil cooler does what it says on the tin – it keeps the car’s oil cool. By feeding the oil through a core that is mounted in an area where airflow is high, the oil’s temperature can be reduced. Oil is only effective up to a certain limit, and if the car’s used on track then the oil temperatures can soon go above the level at which it remains effective. An oil cooler keeps the temperature of the oil to a reasonable limit so that it can still perform as intended.
WHAT IS A DRY SUMP?
Dry sumps offer the ultimate in oil supply and management, but are normally restricted to high-end race and track cars. Instead of having the oil in the sump as you would expect, it’s housed in a remote tank that feeds a constant supply, no matter what the car happens to be doing at the time. A crank-driven pump provides the pressure, so it’s normally directly attributable to engine speed. Larger volumes of oil can be used and an additional advantage is that the engine can be mounted lower in the car as there isn’t a big sump bolted to the bottom – this helps the car’s centre of gravity and improves handling.
WHAT IS AN UPRATED OIL PUMP?
Your car’s standard oil pump will be designed to supply oil for a standard engine. But start factoring in tuning and it’s no surprise that standard oil pumps can start to struggle. Large-rotor oil pumps are available for a wide selection of cars, and as you might guess from the name, they flow more oil than standard. Fitting one is a strong recommendation if you’re running high rpms or big power.
WHAT IS A BAFFLED SUMP?
A baffled sump is designed to keep oil where it’s supposed to be – in the middle of the sump. Additional metalwork in the sump acts as a barrier to stop the oil from trying to ‘climb’ the sides of the sump, providing a constant supply for the scavenge or pick-up pipe to supply the rest of the engine.
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