Many folks remember their first baseball glove and the excitement of breaking it in for a long life of playing catch, softball and the like.
But how? Was glove-oil the answer? What about tying a ball into the glove and leaving it in the sun? Under a mattress? In a dark corner? Should it be rubbed with shaving cream? Maybe it was best to just get out and start playing catch?
Like a baseball glove, new-car engine break-in procedures are often a bit of a grey area. Each manufacturer has a different break-in recommendation for their engines, some being more complicated and extensive than others. In general, not following the break-in procedures to the letter won’t cause serious problems – though a properly broken-in engine is more likely to have a long and enjoyable life.
Your average affordable sedan probably has a break-in recommendation similar to that of the Kia Optima: with no elaborate procedure to follow, but a notice that the vehicle will perform better if drivers follow some simple rules for the first little bit of driving. In the Optima, the owner’s manual suggests spending the first 1,000 kilometres being careful not to race the engine, to keep your engine revs between 2,000 and 4,000, and to avoid travelling at a single speed or rpm for prolonged periods since varying engine speeds are vital to proper break-in as they expose internal parts to a wider range of heat, pressures and stress. Don’t tow a trailer, and don’t let the engine idle longer than 3 minutes, and that’s it, that’s all.
Why the extra initial care? It’s all about ensuring uniform wear occurs between components within the engine. Engine internals work in contact with one another, slipping and sliding and reciprocating against other parts under very tight tolerances – so the surface formed between them is very important.
For instance, the metal piston rings are always in contact with the cylinder wall. A proper surface between the two is vital for engine compression, which ultimately dictates performance and fuel efficiency. Changing engine speed and load during break-in encourages the piston rings to move slightly, which helps creates a more uniform wear surface between the ring and cylinder wall. That’s exactly why many break-in procedures recommend against using cruise control, or a constant engine speed, during break-in.
GM engineers say a relatively high rate of engine wear occurs during break-in compared to the rest of the engine’s life. Through testing, these engineers have determined that most of this wear has occurred by 805 kilometres in a standard engine – after which point speed and load can be gradually increased to maximum.
Chevrolet Corvette, BMW M3, Dodge Viper engine bay. Click image to enlarge
High-performance engines like that in the Chevrolet Corvette Stingray are subjected to more heat, tighter tolerances and higher stresses than a standard engine—and the break in procedure is more complicated, too. The C6 Corvette, for instance, required a lengthy break-in period of over 2,400 kilometres, advising that long-run performance will be improved if procedures are followed. The new C7 Stingray Corvette has a break-in period that’s shorter, falling into that 805-kilometre range.