Engines losing power with age question!
Discussion
Ok, the subject of engine horsepower in higher mileage engines. Its always puzzled me why car engines lose horsepower as the miles stack on. Mainly because I had always understood that engines free up with miles and are tighter when new. However, seeing various rolling road articles involving reader cars with say, 80,000 miles or more on them typically sees a reduction on original quoted BHP of 5-10% or more.
So, what is the optimum mileage on an engine when its freed up, but is new enough not to have lost a few horses?!
Also, is it true that diesel engines tend to not lose as much power as they age, perhaps because they wear less as they aren't so rev happy?
So, what is the optimum mileage on an engine when its freed up, but is new enough not to have lost a few horses?!
Also, is it true that diesel engines tend to not lose as much power as they age, perhaps because they wear less as they aren't so rev happy?
GreenArrow said:
Ok, the subject of engine horsepower in higher mileage engines. Its always puzzled me why car engines lose horsepower as the miles stack on. Mainly because I had always understood that engines free up with miles and are tighter when new. However, seeing various rolling road articles involving reader cars with say, 80,000 miles or more on them typically sees a reduction on original quoted BHP of 5-10% or more.
So, what is the optimum mileage on an engine when its freed up, but is new enough not to have lost a few horses?!
Also, is it true that diesel engines tend to not lose as much power as they age, perhaps because they wear less as they aren't so rev happy?
It depends on how it's been treated, a 200bhp engine driven by an 85yr old from day one will give 190bhp all it's life and do 200,000 miles in 45 years, the same engine driven by a 21yr old will make 200bhp from day one, but will start to decline from 70,000 onwards and probably end being driven into a wall at 81k, one year after rolling off the production line.So, what is the optimum mileage on an engine when its freed up, but is new enough not to have lost a few horses?!
Also, is it true that diesel engines tend to not lose as much power as they age, perhaps because they wear less as they aren't so rev happy?
Town driving doesn't do engines much good, motorway driving does. These are all approximations of course, just to give an idea.
What reduces power is bore or ring wear allowing blow by and less compression, the inlet ports clog up due to the EGR. Cats can get damaged and a few cells melt or clog up, ditto particulate filters and air filters clog up of course. Valve seats wear, get distorted and pitted.
I think there is a lot of rubbish spoken about engines being tight and not giving full power when new, or at least, for how long they do it. On a new car they are run in at the factory so when you get it it's been done. I always feel an engine is fully run in by around 500 miles anyhow. Most of the running in of an engine is done very early on, let's say 50% in the first 10 minutes if done properly, another 20% in a 100 miles, the remainder up to circa 500 miles, but as I pointed out earlier it's far from exact and dependent on how it's done. Engines which are run in fast and relatively hard are often the most healthiest, there is no physical reason why they shouldn't be. The amount of heat radiated from a virgin engine is quite surprising due to the friction - mainly from ring to bore contact.
Yes diesels do greater mileage with less wear due to their lower RPM range.
HTH.
227bhp said:
I think there is a lot of rubbish spoken about engines being tight and not giving full power when new, or at least, for how long they do it. On a new car they are run in at the factory so when you get it it's been done.
Run in from the factory 
Don't be daft laddie, just imagine the enormous cost of running in every engine that leave the production line, it would be completely insane.Mr2Mike said:
Run in from the factory Don't be daft laddie, just imagine the enormous cost of running in every engine that leave the production line, it would be completely insane.
Agreed! Don't be daft laddie, just imagine the enormous cost of running in every engine that leave the production line, it would be completely insane.
This 'run-in at the factory' BS is just an urban myth, based largely on engines needing a lot less running-in than they used to as production and manufacturing methods have evolved over the years. Much better manufacturing tolerances = less on-road running-in required, hence the myth.
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