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A general question about used cars

I’ve always thought that a brand new car needs to be driven very gently (under 50 mph) for the first 500 miles. And no quick starts and stops.

I agree with the advice that it is generally most cost effective to buy a good, used car that’s about 2-3 years old, because a great deal of depreciation happens in the first year or two. But I’ve been reluctant to do so because I keep wondering, how was the car driven for the first 500 miles?

Here’s why I’m saying this. Back in mid-1980’s there were auto brokers, or “buying consultants”. They were not dealers but you could tell them exactly what car you were looking for, down to the color and features you wanted, and they would supposedly not only find the car but negotiate for the best price. For my first car, I used a broker who located my car in Modesto and had it driven to me in Oakland, a distance of about 80 miles.

Well, this car started to burn a lot of oil starting at about 70,000 miles; at around 85,000 miles, it was using one quart of oil every 1000 miles. After it couldn’t pass smog at 90,000, I had to junk it. I had always had the car serviced per schedule. Over the years I’ve often wondered if maybe the person who drove it the initial miles from Modesto to Oakland wasn’t exactly “driving gently” and whether this may have contributed to the short engine life.

When buying a used car, you don’t know how the car was driven in its first 500 miles, but are there things that a mechanic can check or test to be reasonably confident that there won’t be premature issues with excessive oil consumption or smog inspection? Years ago, there was something called a “compression test”, assessing the compression in all cylinders, but I don’t hear much about this anymore.

Your thoughts on this would be most appreciated; this question has been nagging me for years! If this 500-mile rule no longer applies to today’s cars because of new technology, I’d like to know that, too.

With a used vehicle, you have no way of knowing how the vehicle was driven the first 1,000 miles.

Each manufacturer is different about it’s break-in procedure.

But I always recommend driving a new vehicle as if the engine was just rebuilt.

Take it easy the first 1,000 miles.


A used vehicle is just what it is called, used. There’s no way to be 100% certain what shape it is in, but most good inde shops offer a service called a pre-purchase inspection. The good shops don’t just go down a checklist. They do the inspection based on the make/model/year and what a visual inspection and test drive turns up. Then they’ll focus their att’n on those issues.

IMO the way a used 3 year old car is driven the first 500 miles is less important than how it is driven and more importantly, serviced, the next 30,000 miles. One of the items the pre-inspection test focusses on is evidence for the level of routine maintenance the car has seen.


10 months ago I bought a new Honda Fit. The manual says to drive gently for the first 600 miles.

You have to decide whether the price you save on a used car is worth the risk that it may not have been broken in as the manufacturer suggested - or even how it was driven and maintained afterward.

You’ll never really know unless you know the original owner. Good luck.

So the compression test is no longer a recommended test? Seemed simple enough to do. And it was supposed to be quite telling.

The pre-purchase inspection might well involve a compression test, if there’s evidence of questionable compression or oil burning. For example they might inspect the end of the tail pipe for an unusual amount of oily residue.

A compression test?

On some vehicles, it’s almost impossible to get at the spark plugs on the engine alone without removing engine components.

Now you want me to do a compression test?

Open the wallet!



Concur w/the above post, a shop will be happy to perform a compression test if you want one. Provided of course you’re willing to pony up their hourly rate fee. A compression test on my 4 banger Corolla would probably take a shop 20 minutes, but my 8 banger truck would take closer to an hour I expect. Maybe even a little more than an hour. And some engines on newer cars are so crowded it might take over 4 hours.

That’s why the good shops don’t just go down a checklist. If they think your used car needs a compression test they’ll phone you up and ask if you are willing to cover the cost and what the risks are if you don’t. In other words I wouldn’t want to use a shop for a pre-purchase inspection if they always do a compression test.

The OP needs to drag his thinking forward about 30 years.


OK, assuming the spark plugs/cylinders are reasonably accessible, is the compression test still a worthwhile diagnostic test?
Yes, if my thinking needs to be updated and we now have something better for 2013 and later models, like OBD readings, then by all means, I’d like to know that. Can OBD tell if the compression is not quite right?

Be more concerned about suspension/brake/exhaust/steering issues.

When there’s a problem with the operation of the engine/transmission, it’ll a cause a Check Engine light to come on.

But these other systems can have problems, and no light turns on


I have rebuilt a great many engines from 1L 3 cylinders to 472cu in V-8s and never felt it necessary to advise the customer to break them in. Once I rebuilt a Ford 460 V-8 in an F-350 flat bed work truck and when the owner left he loaded a Ford 4000 tractor with a front end loader and back hoe attached on the truck and hooked a trailer carrying a bobcat behind. A few weeks later the owner stopped and asked why his wife’s new Cadillac and his daughters BMW were using a quart of oil every 1,000 miles but his truck was on the full mark after several thousand miles.

Of course the first few minutes a fresh engine is run requires some close attention to noises, pressures and temperature and fast idling for the first few minutes is supposed to get the camshaft 'broken in" but after that normal driving seems to be OK and some of my rebuilds lasted well over 250,000 miles. The vast majority were commercial fleet vehicles.


IMO, when I buy a used car, I’m a lot more worried about structural rust and handling/wear anomalies that suggest the car has been wrecked and ineptly repaired. MOST cars these days go to the crusher with working engines.

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An engine is broken in within the first 5 miles. I strongly suspect that most new cars that end up using oil have suffered from extended oil changes, running the engine oil chronically low, suffered overheating, etc.

Many newer upscale cars and even Harley motorcycles are run full bore on a dyno before even being shipped to the dealers. This is not done on your lower priced garden variety grocery getter cars as a cost saving move.

Other than agreeing with Tester about compression checks being near impossible on the cheap I will add that having great compression numbers does not guarantee little or no oil consumption.
An engine can have fantastic compression numbers and still burn a quart every 10 miles. The compression rings may be fine but the oil control rings may be seized in the piston ring lands.

Rather than a compression test on a newer car a better alternative would be to connect a vacuum gauge. That’s cheap and easy and will show any problems in the engine top end.


It’s actually a great diagnostic test. It probably provides more than other single test about the basic mechanical condition of the engine innards. So if you’d like to have one, go for it. No harm done, other than to your wallet. If it costs $75, no big deal. Me, I’d rather use the $75 for other things. I’d risk a used car purchase w/no compression test if there were no indications one was needed. No guarantees in life and all that. I’ll throw the dice on that one.

I’ve done compression tests on all my vehicles at least once as part of routine maintenance to document the engine function. The tests all showed no compression problems. One time tho I had a balky starting lawnmower. Nothing else worked to correct the problem so I took it apart and replaced the piston rings. Sure enough, the old rings were definitely worn out. Replacing the rings produced a like-new starting lawn mower. It really had some zip. Unfortunately soon after the magneto failed and the lawn mower ended up at the metal recyclers. With new rings.

Well, there are quite a few new cars that have been driven gently and still burn oil. So there goes that sense of security. Actually the OM on the new cars states that you should also vary the speed over the first 500 miles and not to cruise at a steady speed.

I look at my used car purchases over my life time. I have bought quite a few cars, maybe 1-2 that I had to sell sooner than planned but none were lemons. Even if I get a lemon on my next car, I am still ahead. You just have to do you due diligence.

You can never be safe but you can try.


I’ve bought 10 used cars over the last 48 years and only one, a 1957 Plymouth bought for $325, turned out to be an oil burner.

There are a number of things you can check out for yourself, checking the dipstick for any unusual deposits, driving the car and letting off the gas while watching the rear view mirror for any smoke, checking and verifying the maintenance records.

Hidden rust and unreliable electronics are the two biggest risks in buying a used car these days.

Something to think about. Today’s newer engines are fitted better and use more advance materials for longer life. I wouldn’t worry too much about how it was broken in. Ever watch the guys that drive the vehicle around at the stock yards? No body warms car up anymore. Just don’t buy one that was a rental car. Those are what I call really abused cars.

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I had a temporary job at a shipyard where imported vehicles were offloaded and stored until they were shipped to the dealers.
The job entailed driving the cars from the storage lot to the carwash located on the site and then drive the clean cars to a lot where they were loaded onto tractor trailers for deliver to the dealers.

To make a long story short lets just say that those cars were not gently driven by us car jockeys.