If we are looking to save fuel in a new and more economical car, we should be thinking about the process of “running in” the new engine to best effect – in this context meaning to obtain the best fuel economy. Now, more traditional methods of running-in engines have suggested the approach of slowly increasing your engine speed and load with mileage until, after some 1,000 to 1,500 miles, you can feel free to do as you wish, although the more cautious of us might not really open up the engine until we reach 2,000 miles or more. But the official words from Audi throw some light on the subject, and are possibly more in line with today’s engine technology. They say:
The running-in phase is completed after approximately 20 hours, equivalent to a distance of 600 to 900 miles. It is relatively easy to run in a new engine correctly over the first few miles if you observe the following:
• When cold-starting the engine, always run the engine to warm gently. This will help considerably in making the engine last a long time.
• Vary the engine load when driving on the motorway for the first time: change the load condition and only run the engine at very low or very high revs for short periods. The accelerator pedal should only be pressed right down in emergency situations.
So it seems then that the rather protracted and gentler running-in approach that many of us might still be tempted to take means that we may well wait a long time for our gently run-in engine to give its best, power-wise and on the economy front. We do know for sure that, if you treat a new engine too kindly, you may never run it in properly, and consequently may suffer permanently from high oil consumption, as the piston rings and cylinder bores may never acquire the optimum sealing properties. In our experience of running-in engines of new cars, we have mostly followed traditional wisdom and, whilst we’ve never suffered high oil consumption, our fuel economy has improved slowly and steadily, but over tens of thousands of miles. So maybe expecting a diesel engine to be only “at its best” after 30 to 50,000miles is wrong, and this most desirable state can, and should, be attained far more quickly, and without compromising the engine life?
A running-in period is obviously still critical to the overall engine life and the long-term durability of the engine, but the bedding-in period required can seemingly now be significantly reduced, with new piston ring materials, diamond cylinder bore honing, bore micro-surface treatments, and today’s better quality oils. Pistons and rings of engines with silicon carbide/nickel coated aluminium cylinder bores certainly bed-in faster than in traditional cast iron cylinder bores, whilst cast iron cylinders are increasingly now being given UV laser and other surface treatments – both helping avoid the relatively heavy early oil consumption that was once to be expected with most new engines. Such treatments aim to create micron-sized “pockets” in the cylinder bore that hold lubricating oil and thus reduce bore friction and wear, and improve the gas seal. Apparently, at 100,000 miles such cylinder bores are showing very little measurable wear and the resulting emissions performance is almost as good as new – a key factor if in-service emissions testing comes to pass, as it well may.
We therefore think we can feel quite confident that it’s right to give any new engine a lot more work earlier than we might have done in past times. We should now look at giving an engine short spells of fairly hard work after 200 to 300 miles, followed by even harder intermittent work, gradually approaching full throttle and maximum power, after around 500 to 600 miles. This possibly goes somewhat against the grain for economy drivers; by our nature “economy driving” during the first 1,000 miles comes naturally to us and yet, in doing so, we slow down the process of getting the engine up to peak performance and economy. We always say that giving an engine some healthy hard work at the right time doesn’t necessarily waste fuel and again, in more wise words from Audi: “Rapid acceleration and changing up early has a positive effect on energy consumption.” That’s also very similar to advice that which we’ve given on avoiding diesel particulate filter (DPF) regeneration problems. Warm the engine up properly and then, after a few hundred miles, take opportunities to accelerate more and more enthusiastically, yet sympathetically, and you’ll have your new engine run in more swiftly.