"I always looked after my own cars. Change the oil, cleaned the spark plugs, all that kind of stuff. What is it about modern cars that make that not such a good idea?"

Kevin Tremblay answers..

Wow. Where to start with that? Okay. So modern cars, why it's not a good idea to fix it yourself in the driveway, whether you're a parent or anybody who's taken with cars in the past, right? Cars have altered a lot just in the past couple of years, but let's take the last 15. Okay?

So something as simple as spark plugs, which we used to do on, you used to do them on your own car back in the eighties, right? Big difference now. All of the engines use aluminum cylinder heads. They don't use cast iron cylinder heads. What does that mean to you? Well, now you've got a steel spark plug threading into an aluminum block.

It's a different metal combination that we never used to deal with. It's also very fragile. So if you don't know the right torque specs, sorry, torque specifications for tightening or removing that spark plug and you haven't thought about how to carefully remove something from an aluminum cylinder head, you might very easily damage your motor when you're just trying to save yourself some money on labor, but now the cost of repair becomes massive. If you can even repair the aluminum cylinder head or the shop might tell you, "Sorry, you need to replace the top half of your motor." And that's several thousand dollars. That's just one thing, spark plugs.

Other things like air filters, for example, back in the olden days, a car didn't pay attention to air flow too much. So as long as there is air coming in, the engine was happy and that was about it. Nowadays, the computer is measuring the flow of air into your engine, down to the grams per second. So if you put in an air filter that fits, but is the wrong flow rate, you might cause yourself a warning light or some running issues or some lean running or something like that. And then you'll be chasing your tail, trying to figure out why you've got engine running problems when it goes back to, "Oh, you put it in the wrong air filter." And you didn't know you put in the wrong air filter because you bought the cheap one at some store and didn't think about what's the flow rate, and does it match my car?

So cars are so ridiculously advanced now with the computers watching everything that if you don't put in the right thing that the car is looking for, it will tell you it's not happy. You will get the warning light, you might get driving concerns, and then because most people haven't learned and kept up with how to diagnose a modern car the same way a technician does.

You might have a code scanner at home and you'll hook up the code scanner. And it says, "Oh, you've got a code for O2 sensor, for the rear O2 sensor." And you go, "Ah, it must be the O2 sensor." And you go and you put in the O2 sensor and a week later, the code comes back and it's the same code. And you're left wondering, "Maybe I got a bad part." So you warranty the part, get another one, put it in. Code comes back. And now you're wondering, "Why do I keep getting a code for an O2 sensor? I already replaced it."

Well it's because the cars often set... A code doesn't necessarily mean that's the part that's bad. It's just like pointing to, "Here's an area that I see a fault. This doesn't make sense to me." So the computer's raising a flag saying, "Hey, something about that rear O2 sensor, I think doesn't make sense to me."

But it might not be the O2 sensor that's bad. The O2 sensor might be telling you the truth and the readings that look bad are because something else is going on ahead of it. So that's why. Look, it's just going to cost you a lot less money if you take your car to a shop that knows how to fix your car, that's got the tools, they've got the experience and the knowledge versus trying to monkey around with it yourself.

You're welcome to do that and we do have lots of customers to do that and we tell them, "If you run into something you can't handle, you can phone us." But financially speaking, at the end of the day, none of my customers have found it to be cheaper doing it themselves. I could phone up any one of them and they'll say that.

The Garage can offer flexibility and freedom to be in control of your car’s maintenance in a way that dealers cannot. Discover the reason why.

What’s your story?

Tell us about your experiences—good and bad—concerning your relationship with your auto maintenance supplier. Scroll down and add them in the comments box below. We all love great stories and the best ones posted below, by the end of July 2016, may qualify for a nice surprise! Sign up below and we’ll be sure to let you know.