Do big engines last longer than smaller ones and, if so, why? Marco
Engine age and durability are usually expressed in time and the distance the vehicle has travelled…neither of which determine the “rate” of wear!
The true longevity of an engine must be measured by the number of times it has turned (i.e. the crankshaft, not the wheels), in parallel with how hard it has had to work (speed, load and the gearing required to manage it)
To add to the potential confusion, we measure revs per minute, speed in hours, distance in metres, and age in years. Then there are other aspects of driving style, service diligence, quality of lubrication, predominant type of use, road and topographical and climatic conditions…
So to answer your question we have to simplify and standardize and average all of that and test the result with some arithmetic. Let’s see…
We can guesstimate that most cars in a mix of conditions spend most of their moving time at or around 60 kph, on average using 4th gear, let’s say.
To do that a small car will rotate the crankshaft about 2,000 times per minute (to get the requisite amount of power from a small motor).
In an hour, that is 120,000 times while covering a distance of 60 km. By the time an engine has done 60,000 kms, that is 120 million rotations.
A 3.0 litre engine will do much the same thing at…1,500 revs per minute. Driven in the same way and with all other external conditions being equal, its engine will have rotated only 90 million times to go 60,000 km. Conversely, by the time it has rotated 120 million times, it will have done 80,000 kms.
From this single aspect of longevity and durability (which we tend to measure in distance) it would seem that bigger engines “go further” than smaller ones.
Ergo, they last longer – in distance. And empirical evidence would suggest they do. Tales of big engines achieving lifespans of half-a-million kms or more are plentiful. Small engines reaching those levels are rare, even at half that distance.
It should be stressed that this does not confirm engine capacity as a prime determinant. It suggests they are driven differently. There are many other factors (even the budgets and lifestyles of owners of different types and size of car) that could explain that outcome.
Another way to explore this issue would be to put a 1.0 litre engine and a 3.0 litre engine side by side on a test bench and run them both non-stop at the same 2,000 rev speed, with an unlimited circulation of fresh lubrication and fuel but no load, and see which one “wore out” or “failed” first. I suspect they might be similar enough to rule out “engine capacity” as a direct cause. The test would take a while.
To save the battery on your pocket calculator, an engine that has done 500,000 kms has probably rotated about one billion (!) times. And as a reminder of the real difference between a million and a billion: One million seconds is about 11 days. One billion seconds is about 33 years.
One million engine rotations at 2,000 rpm would take about eight hours and get you from Nairobi to Mombasa. One billion would take nearly a year (24/7) and get you to the moon (about the same distance as ten times round the world).
