At what point financially does it make sense to get another car?

Most mechanical components follow a so-called “wear out curve” or “bathtub curve”, where after a long period of low probability of failure the chance of failure rises rapidly. With good Japanese cars that rate of increase would be at about 200,000 to 250,000 miles. With a Fiat or similar low quality cars, the curve starts to go up at 100,000 miles or so.

This assumes proper maintenance according to plan…
So, if you buy a good Japanese car with 200,000 miles on it there will be some repairs in the near future, maybe not the main engine, but other components have a higher probability of failure.

On a Nissan we owned, the CV joints and axles, alternator, starter, all went before 200,000 miles.The steering rack started to go just before we sold it.

Years ago with US cars, at 100,000 miles the starter, alternator, a battery, U joints and other components were expected to fail.

Shoot, years ago at 100,000 miles people came over and insisted on verifying the odometer reading themselves, because they didn’t believe you when you told them your car had rolled to 6 figures. :wink:

So you are saying the odds of anything going out in a car is the same whether the car is new or it has 200K miles on it?
I guess you are right that my source is “anecdotes”, but I want to see a source that says mileage and age has nothing to do with the odds of breakdown. Seems like other posters agree with me more or less. Right bellow my post @Docnick is making similar statements.


Yes galant! Failure generally increases with age or use but at some point the "failure curve " goes up very steeply.

In aircraft maintenance these “inflection points” are carefully calculated and after a certain number of operating hours engines and other equipment is taken off line and inspected and or overhauled.

On the other hand, much electronic equipment will experience “random failure” (rather than wear out) which is unpredictable.and can happen anytime.

Companies use statistical analysis of past failures to plot a curve as to when these items may fail.

I remember studying a topic called reliability engineering where components of a machine were all designed to have about the same life expectancy. In an automobile it wouldn’t make sense to have an engine last 1,000,000 miles when, if the motorist drives 15,000 miles a year, the body rusts out in 12 years when the engine has gone only 180,000 miles.
How an automobile is used makes a big difference. I bought a new Oldsmobile Cutlass Salon in 1978. It had 240,000 miles on the odometer when I sold it 33 years later. However, it had long since become an “around town” car. When the Oldsmobile had 100,000 miles, I let my son take it to college which was 50 miles away. The next year, my son was on an internship 400 miles from home. I put him in a car ten years newer because I didn’t want him stranded on the highway.
I could do the maintenance and many of the repairs on the 1978 Oldsmobile. After my son was in a newer car, it made sense to keep it to hack around town and commute two miles each way back and forth to work until I retired. At that point, it made sense to get rid of the car and use the minivan for everything.
At the campus where I taught, I saw some of the vehicles which were used for out of city travel become used for just local transportation. Ultimately, these vehicles go to a surplus auction and another road vehicle is moved down for local use.
When I moved 120 miles to go to graduate school, we rented a U-Haul truck on a return basis to save costs. The truck had stenciled on the front bumper “For Local Use Only”. That truck burned two quarts of oil going down to our new location and two quarts coming back. I had to double clutch shifting gears to prevent the gears from grinding. This truck clearly wasn’t supposed to be doing intercity travel, though it was probably o.k. for local moves around town.
My point is that the decision on whether to repair or replace depends on how the vehicle is to be used.
Financial consideration also comes into play. In his book “What You Should Know About Cars”, published in the early 1960s,the late Tom McCahill addressed the problem. He gave the example of an over the road salesman whose wife just sprung a new offspring on the family and was in a temporary financial crunch. The salesman had a car with 75,000 miles that was using oil. In this case, McCahill said that if the salesman only needed another 25,000 miles, having a set of expansion piston rings installed and a valve job might do the trick. On the other hand, for longer service, a newer car would be in order.

Excellent point! I did reliability engineering and maintenance consulting for 20 or so years and the use-specific decisions always dictated that the bets and newest equipment be used for the most demanding service.

I remember visiting a major chemical plant in Texas and having to park my car at the gate.

An office worker picked me up in a 70s Ford pickup truck, totally out of tune with the ultra-modern plant.

When I asked he said the truck only had 40,000 miles on it and was totally reliable, so why change it!

I don’t know if there is a source for that, but most engineers are given a target “service life” for designing parts for a vehicle. That can vary from manufacturer to manufacturer. This is not just for vehicles but for just about everything you buy.

Therefore, unless there is a defect that causes an early failure, you really can expect a vehicle to “fall apart” over a relatively short period of time. It probably wont happen weeks or month apart but usually within a couple of years and 50 to 75k miles.

The design service life is based on fixed parameters of driving conditions and maintenance. There will be quite a variation in actual service life depending on how the vehicle is driven, where it is driven and how it is maintained.

This is why people who buy and sell a lot of cars who are not dealers will not buy a car with a rebuilt engine or transmission. They would rather buy a car with 200k that is in very good condition and runs like new than the same vehicle with 100k and a recently rebuilt engine or transmission. They know that if it needed a rebuild that early, it has been rode hard and put away wet most of its life.

Edit: There is a poem by Oliver Wendell Holmes called “The Deacons Masterpiece” aka The Wonderful One-Hoss Shay. In the poem, a deacon crafts a one horse shay that is so well built and designed that it could not be broken. One the one hundredth anniversary of its completion, it had never broken down and then all it once it fell completely apart.

I think this poem may be the source of why people have the belief that once one thing fails, everything else will follow, but it is true that engineers do design to fit an expected service life or at least a minimum service life. It’s not good for your career if the parts you design chronically fail first.

There are countless surveys and articles published about long lived cars, those with 400,000 miles or more.

In all cases the owners selected cars with “good genes” such as Lexus or Toyotas and others.

In all cases they replaced items as they wore out or just failed. Obviously an alternator won’t likely last 400,000 miles and neither will the struts.

What sets these cars apart is the superior quality of their parts as well as main major components like engine and transmission…

I once worked with an engineer who had a Jaguar E Type and at 90,000 mile he told me that “everything” had been replaced and the engine had been overhauled.

He made enough money to do all that, but is shows that Jaguar had no priorities for long life cycle parts.

Honda, Toyota and others work to Six Sigma quality, which means one defect in about 340,000 parts Lucas Electric tolerated 10% defects on their assembly line meaning many borderline defective parts made it in the vehicles.

Most quality oriented firms do life cycle testing to ensure predictable long life.

Caterpillar,and other heavy equipment manufacturers all do this.

Russian Belarus tractors failed miserably in the North American market because they were thrown together without any serious endurance testing and quality control in the plants was virtually absent.