DIFFLOCK.com

As 4X4 enthusiasts, you probably all know about the general ins and outs of taking care of your vehicle, however, not much is normally said about engine oil. The truth about oil is that it serves as the blood of the car’s engine. Without lubricants, the engine would seize up and be useless, leaving the owner with a hefty bill. Drivers tend to know more about tyres, shocks, exhausts and wheels, however when it comes to oils, most are chosen without consideration of the correct grade for the engine and its use.

The way in which cars are made today means that the owner sees less of his or her mechanic. Some car bonnets are now even sealed to keep the owner out – only allowing the driver to check the oil, dipstick level and allowing top-up. The fact that the owner is allowed to check and top up the oil levels demonstrates how important it is to regularly check the levels.

Engine oil has a huge job and many roles to fill. To get a bit technical, it has to maintain a protective film to prevent metal on metal contact, and do this at all times while under extremely high temperatures and pressure. The texture is very important; it must be thin enough to allow easy starting and circulate quickly through the engine, yet remain thick enough at high temperatures to provide adequate lubrication.

To maintain optimum performance, oil has to effectively coat the cylinders and rings to fill in the microscopic pores and gaps that would otherwise allow reduced compression. It also interacts with gaskets and seals to help them prevent leaks and hold oil pressure. In addition to all of this, it prevents rust and and neutralises acids from forming through the combustion process.

That’s what your engine oil needs to do – now, how do you find one that fills all of these functions as well as the specifications for your vehicle?

What’s in a name?

Viscosity.

You’ve probably heard of it, maybe you have an idea of what it is, but how important is it in choosing an engine oil? Viscosity is one of the most important properties of engine oil and helps determine whether the oil will be suitable for your vehicle. Viscosity is a measure of the oil’s resistance to flow – the thicker the oil, the higher the viscosity and the less it ‘flows.’ Oil that is too thin will not provide adequate lubrication - imagine water just running off of the engine - and too thick would take too much time and energy to run through the engine, like honey.

The Society of Automotive Engineers (SAE) years ago decided to establish numbers to correspond to a viscosity and other characteristics at a certain temperature. These grades, running from 5W to SAE50, are still the ones we use today although being updated regularly over the years.

In 5W, what is the ‘W’?

The W was added later to the viscosity grades and stands for ‘winter.’ However, technically speaking, it means that the oil has passed tests that make it still function at extremely low temperatures. Very simply, oil that flows more quickly when cold has a lower viscosity and, consequently, is given a lower grade. For example, an SAE 30 grade covers a lower range of temperatures than an SAE 40 grade. In the winter in cold climates, people often choose to use a lower viscosity, like a 30 grade to ensure that the oil flows properly in cold weather. If you think of the ‘honey’ example again, in winter, it is thick and doesn’t flow easily whereas in the summer it is much more fluid. Engine oils can work in the same way – and therefore must be created to still do their job at varying temperatures.

Temperatures: what about 4X4 vehicle engines?

Most modern engines need oil that both lubricates well at start-up and continues to protect a hot engine – some engines can have temperatures greater than 300&Mac251;F. One way to take care of this is by using a multigrade oil, such as 0W-40 or 15W-50, the number after the W indicating viscosity at high temperatures. The easiest way of analysing this oil is that it is simply a 0W or 15W grade oil that increases to a 40 or 50 grade oil when hot. If performance and hot protection is all that is required go for a 15W-50 oil, it will keep those vital components further apart. If cold start and economy are the main interest then go for a 0W-40, it will create less drag whilst still giving excellent high temperature performance.

Why synthetic oils?

Basically, synthetic oils are the purest extracts from crude oil, isolated to give the best performance required by the engine. Conventional mineral oils have impurities which can cause contamination when they get hot. Conventional mineral oils could thicken with the engines normal running temperature and burn fairly easily leaving a black syrup in the sump which might disrupt starting. Mobil 1 is a fully synthetic oil used with great success by most informed race and rally teams such as McLaren Mercedes. Synthetics flow easily using less effort to turn the engine creating faster lubrication and more accessible power.

Leading in performance : 4X4 vehicles and Mobil 1 oils

There is an unofficial yet growing practical relationship between 4X4 vehicles, 4X4 enthusiasts and Mobil 1. "4X4 vehicles are unique in their own right. Mobil 1 oils are suitable for most 4X4 vehicles because of their ability to perform in various temperatures and when engines are pushed to the limit during off-roading," comments Richard Potts, part of the ExxonMobil National Accounts Team for Mobil 1 and avid 4X4 enthusiast owning a 1982 Jeep CJ7.

Off-roading with 4X4’s and Mobil 1

Two off-roading events took place this past year in Kielder Forest Northumberland with a number of Jeep vehicles in attendance. The 4X4 Weekend Jamborees were the first of its kind in the North of England. Each vehicle was required to drive the 60-70 miles safari route in convoy. The weekend provided great off-roading with a BBQ and entertainment on the Saturday evening. Due to the success of the 2001 events, there are three more of these events being planned for 2002 in May, July and September. The 2001 events were completely booked within two weeks of being advertised. If you are interested in taking part in 2002 please contact Richard Potts from ExxonMobil on 01670 730 732 or email him at richard.d.potts@exxonmobil.com.