Unless you are mechanically minded and understand the workings of an engine and the dire need to use the right oils in it, you will find it hard to comprehend the horrific consequences to your engine and many of the components bolted on to it, to aid its performance, of using the wrong oil, or starving your engine of oil.
Think of it like this. Your engine is like your body. It has many components to make it work more efficiently - your oil pump is like your heart, your EGR valve is like your lungs filtering the fuel it takes in, the alternator is a bit like your digestive system - keeping the batteries charged.
Your car needs a balanced diet to run at its most efficient - as the saying goes you are what you eat. Cheap and inferior oils are like the fast food of the motor industry - over time in much the same way as your arteries will clog with cholesterol, the carbon clogs up the oil galleries throughout the engine, oil pump, EGR valve and turbo. Eventually this will cause a total blockage and give your engine a 'heart attack'. As with human beings this heart attack could be minor and affect any of a number of areas - such as the oil pump, turbo charger, EGR valve. If your oil pump fails your engine will most likely sieze - the vehicle equivalent of a fatal myocardic episode (okay okay - heart attack then!)
Your particulated filter (PTF) is like your endocrine system (liver, kidneys, lymph glands) - it provides ongoing filtration of all the toxins that otherwise would clog up the cars system.
In your average journey your engine is probably turning over at 1500-2500 revolutions per minute. I'm not even going to calculate how many times your engine turns over in a half hour journey - lets just say its a lot. In much the same way as you would eat properly before doing a marathon, and would make sure you topped up with nourishing food and fluids along the way, its vital that your engine has a steady flow of proper good quality oils to make sure it performs at its optimum, remains well lubricated and isnt left exhausted by trying to cope with the amount of carbon being produced.
Most manufacturers are designing engines now to produce a lower carbon footprint (emission output) - this means that as the carbon has to go somewhere, if its not going outside the engine, its staying inside. So the better the quality of the oil, the less carbon is produced, and so the less stays in your engine. To help your engine help you, its vital to have your engine serviced on a regular basis with the right oils.
Poor 'food' for your car will lead to poor results, and over the longer term possibly fatal engine problems - its worth the extra few pence to put the proper quality and grade of oils in your car to keep it in prime condition. After all its better to fork out a few quid for some good oil now, rather than having to spend several hundred on a replacement turbo.