What makes some cars last longer than others?

Dear Car Talk:

Reading the recent question from Coop about his '95 Mini that's crapping out after 99,500 miles made me wonder why some brands of cars start falling apart at 100,000 miles, and others (Hondas, for example) trundle along with few problems for 200,000 or even 300,000 miles. Is it good genes, good diet, clean living or what? Your comments, please. – Steve

RAY: Yes. It's mostly good design and good manufacturing. I remember as recently as 10 years ago, we'd have a Toyota Camry in the shop with 180,000 miles on it, and the engine would be running as quietly as if it had 18,000 miles on it; you might not even know it was running. And in the next bay, there'd be a Chevy Cavalier with 80,000 miles on it that was rattling like a loose set of false teeth in the outhouse on a cold morning.

Now, all cars have gotten better in the past few decades. It’s important to give credit where it’s due. Overall, all cars are more reliable, better made and last longer than ever. But some still are better than others. Consumer Reports (which tracks reliability as well as anyone) lists the 10 most reliable cars every year. And in its most recent list, Toyota (which also makes Lexus) took five of the top 10 spots.

Why is that? Well, we know that Toyota long ago decided to stake its reputation on reliability. It made that the top priority. It could have prioritized styling – and if you’ve seen a Camry in the past 35 years, you know it didn’t do that. It could have emphasized exciting performance – and if you’ve driven a Camry in the past 35 years, you know it didn’t do that, either.

What it did do is put a lot of effort into designing parts that last, manufacturing them well and assembling them so that the spaces between the moving parts (called “tolerances”) are tiny. That makes engines run quietly and run longer, since the pieces aren’t knocking the heck out of each other a thousand times a minute.

In some cases, those improvements involved better design and engineering. In some cases, they involved training and incentivizing employees. And in other cases, they involved spending a little more money on parts or materials.

Other manufacturers had other top priorities. Some focused on performance, some on styling, some on the next quarterly return for their shareholders. Toyota bet that if it could gain a reputation for building cars that were reliable and lasted a long time, it would eventually pay off. And it did.

Now, there still are people for whom reliability is not the very first thing on their wish list. Some are moved more by styling, some by fuel economy, comfort, safety or high performance. And some just say, “Screw the reliability ratings, I want that cute little box on wheels!” And there’s nothing wrong with that. Caveat emptor.

But the reason Toyotas and Hondas have long been leaders in reliability and durability is because they made those things priorities over many years, and measured and improved them month after month after month. And while others have gotten closer, they’re still working to catch up.

Problem with air-flow sensor could be simple fix, or could signal impending doom for engine

Dear Car Talk:

The mass air-flow sensor on my beloved 1999 VW Eurovan camper has been replaced three times, and now it's gone bad again. The mechanic who looked at it said there was oil on the sensor. What would cause that? And any idea what it would cost to fix? – Meredith

RAY: You know all those quarts of oil you've been adding to your engine? Now you know where they're ending up.

It sounds like you have an affliction we call “blow-by”: When enough motor oil sneaks by worn-out piston rings and then gets combusted in the cylinders, oily vapors can get blown back into the air-intake area, where the mass air-flow sensor lives. And if you get enough oil on it, you can muck up the sensor’s electronics and cause it to stop working.

If you do have blow-by that’s that serious, an oily air-flow sensor won’t be the only piece of evidence: Your mechanic undoubtedly would see an oily film all over the air filter, too.

The best-case scenario for you, Meredith, is that whatever blow-by your engine is producing is being exacerbated by a bad PCV valve. The PCV is supposed to remove combustion gases from the crankcase, and recycle them through the air intake so they don’t build up – and blow back.

If your PCV system isn’t working anymore, that could explain why those gases, and the oily vapors, are getting blown backward and fouling your airflow sensor. A PCV system might cost you a couple of hundred bucks to repair.

The worst-case scenario is that your PCV system is working fine, which means it just can’t keep up with the massive amount of blow-by your engine is producing. That would mean you’re on a countdown to an engine rebuild. That’s thousands.

If you’re looking for a shorter-term solution, you also could try cleaning the sensor that failed. Normally, they fail because a wire breaks. But if yours is just smothered with oil, you can try using contact cleaner (not the Bausch and Lomb stuff for your contact lenses, the stuff that cleans electronic contacts) to clean off your sensor and see if you can get it working again.

Or you can simply invest in mass airflow sensor futures, Meredith. Maybe you can get a case price from Murray the Airflow King. Good luck.