The Engine Mistakes Quiz


By: Dave Davis

7 Min Quiz

Image: LeoPatrizi/E+/Getty Images

About This Quiz

A car's engine is a complex beast, and it needs care and regular maintenance to perform at its best. But do you know what's best for the engine? Most of us never took auto shop in school, so everything we know about engines tends to come from mechanics explaining what just went wrong with ours (after a costly repair), or stories from our friends and knowledge handed down from our parents. Added together, we often think we have a handle on the situation, but do we really? This quiz will test your knowledge of how to best take care of the beast under your hood. Do you think your knowledge is up to the task?

Older cars were easier to work on (today's are more advanced, with fewer "user-serviceable" parts and processes), but some old misconceptions are still handed down from parent to child. Is it OK to warm a car up on a cold morning? Is a "check engine" light just a trick to get you into the service bay? What's the one thing you might be doing without thinking about it that could be damaging your transmission? The answers to questions you might not think twice about could surprise you!

Cars have also evolved. The answers we thought we knew might change over time. Do you know when to get your oil changed? What about your transmission fluid? Is synthetic oil bad for your car? Some of these questions might be easy, while others might give you a rude awakening. It's time to put your knowledge to the test and see if you really know as much as you thought. Let's go!

Congrats! You just bought a brand new car! What's the worst thing you can do to it at this moment?

There's a temptation to rev and push a new car to see what it can really do before the ravages of time start to take their toll, but resist that urge for a little while. The engine will last longer, have fewer issues and ultimately perform better if you take it a little easy and keep the RPMs in a sensible range in the beginning. Recommended "break-in" times vary by vehicle, but giving it 1,000 miles is a good rule of thumb.


Which of these activities is worse for the transmission?

Changing directions without coming to a complete stop puts a lot of stress on your car — particularly the engine, transmission and axles. Just take a second to stop, and then change direction. Your engine and powertrain will thank you!


Which of these statements is true?

Resting your hand on the gear shifter in a manual car might seem harmless — how much damage can you do to the transmission single-handedly? — but it can prematurely wear small parts, such as bushings and synchronizers. You should leave a two-second space cushion between you and the car in front of you, don't ride the brake, and any radio can be distracting, depending on what's on.


You would never let the oil in your engine get too dirty or too low, would you? Of course not. So how often should you change the oil?

Check your car's specific recommended maintenance schedule — the guidelines can vary from car to car — but, in general, modern vehicles require an oil change about every 5,000 miles. Also, no oil is self-cleaning.


When you're at the pump, you splurge for the highest octane fuel available. Was that a mistake?

The octane rating on gasoline denotes how compressible it is — the higher the number, the more compressible it is, which means more fuel can be injected into the cylinder for more power. While high-performance cars can make use of this fact, consumer vehicles are engineered to run just fine on the lower octane gasoline (and won't benefit from the more expensive stuff).


True or False: It doesn't matter how much gas you keep in the fuel tank, as long as it doesn't run dry.

Providing fuel for the internal combustion process isn't the only thing gas in the tank does. Some fuel pumps are designed to stay submerged in fuel as a way of cooling themselves off. If the fuel tank runs almost dry, the pump's life will grow shorter and need replacing sooner.


Engine rebuild pro tip! When installing new oil-control piston rings, which of these statements is true?

If you install an oil-control piston ring (which is the second of the three rings on the piston), make sure that it's installed right-side-up; otherwise, the oil will leak, smoke will form, and you'll be embarrassed in the auto shop. It just takes a second, so make sure you're putting them on in the right direction!


What happens when you mix different types of antifreeze?

There are generally two types of antifreeze: the traditional green/yellow type and the "Dexcool" orange/pink type. While they are designed to perform the same function, they are very different chemicals and, when mixed together, can form a gel that will clog your radiator and stop it from functioning. Just say no!


What's the best course of action when the "check engine" light comes on?

The "check engine" light can be maddeningly enigmatic, but it really is trying to tell you something. When it comes on, check the other lights/gauges to see if there's an overheating or oil pressure problem. Next, make sure the gas cap is undamaged and on tight. If it's still on, you probably need to schedule a service appointment. However, if the light is blinking (or red), there is a serious problem; get to the garage!


You've just made a classic mistake and "lugged" your engine. What did you do?

When you "lug" your engine, you're accelerating while in high gear. It's better to downshift if, for instance, you need to speed up to pass someone. That's because, at high gears, your engine has to work much harder to do the same amount of work. This is especially bad for engines with turbochargers.


You like to "accelerate to the stoplight." What are you doing to your engine over time?

You know the type of driver we're talking about — you might even be that driver. In city driving, they are quick off the line when the light turns green, accelerating down the block only to have to hit the brakes for the next red light. That high-power start and stop is hard on your vehicle, especially its engine and brakes. Steady driving is much better for the automobile.


Have you ever had your old car's power steering system flushed? No? If you want to get the best out of it, how often should you have that done?

It doesn't need to be done very often, but, in general, cars can benefit from having the power steering system flushed and refilled every 75,000 to 100,000 miles. If the car is becoming hard to steer or starts making squealing, groaning or whining noises, you should have it checked out.


Don't let that time bomb tick! When is the best time to change your vehicle's timing belt?

The timing belt keeps the camshaft and crankshaft in sync, which is critical for the internal combustion process. If it breaks, the car stops. The tension and condition of the belt should be checked every 15,000 miles or so, and should be replaced every 60,000 miles, just to be on the safe side.


If it's taken care of, should the battery ever have to be replaced?

Batteries will naturally lose their ability to hold a charge over time. Generally, three years is a good, dependable lifespan for a battery; the older they get, the less reliable they will become. If you're in that zone and the weather is starting to turn cold, do yourself a favor and change out the battery.


You know you shouldn't run a car with too little oil (right?), but will there be a problem if you put too much in?

Each vehicle is designed to have a certain oil volume for optimal performance — no more and no less. When too much oil is added to the system, the increased pressure puts strain on seals and gaskets within the engine.


When you get a notice of a safety recall for your vehicle, which one of these actions is NOT a mistake?

The National Highway Traffic Safety Administration (NHTSA) will issue a recall when it — or the manufacturer — determines there's a safety problem with a certain make or model of vehicle. It can be a hassle, but it's for your car's — and your — own good to get your vehicle to a qualified mechanic to get the problem taken care of.


You start to notice a puddle forms under your car when it's parked for any length of time. What is the one thing that you should NOT do?

Except for the water that drips from your air conditioner (this condensation is normal), puddles under your car are never a good sign and shouldn't be ignored. Try to identify the fluid (the six most common are water, motor oil, transmission fluid, coolant, gear oil and power steering fluid), and note where you think the leak is, based on position, to give your mechanic a clue of what to search for.


Engine rebuild pro tip! Should the cylinder walls be completely smooth when you're finished?

Piston walls have a slight crosshatch pattern in order to better maintain lubrication from the oil. If they are finished smooth, the piston rings won't last as long. Also, if your pistons are rotating, you've done something seriously wrong.


True or false: It's best to let your car warm up on cold days before driving.

It's tempting to start the car on a winter morning and go back inside for five or 10 minutes to allow it to get toasty, but the reality is that you're harming your engine. Just letting it idle doesn't allow the engine to warm as quickly as it would if you were driving, meaning the oil isn't being circulated as well, and the parts aren't getting proper lubrication for a longer period of time.


Some say that synthetic oil can cause leaks in your engine. What's the truth in this situation?

Synthetic oil does not cause leaks, and it can extend the life of your engine. What it sometimes can do is reveal leaks that were already present. The synthetic oil can do a good job of cleaning deposits — sometimes too good because those deposits were the only thing plugging holes in the system.


You keep it nice and unused. Does it harm a car to be driven too infrequently?

Inactivity can harm certain elements of your vehicle — particularly the battery and the tires — so you should make a point to drive the car a bit every week. Just like you need exercise, your car needs some roadwork!


Which of the following is true about the fluids in your car?

There are several fluids in your car and engine that need to maintain a certain level and quality to maintain good operation. Some of these fluids you can check periodically on your own and top off if needed, while others should be checked during the course of regular maintenance. You DO have regular maintenance performed, right?


Which of the following is true when it comes to noises that you hear while driving?

Besides the on-board diagnostic system and, well, breaking down, your engine and other vehicle systems will often tell you what they need by the sounds they make, and it's best to pay attention. Noises ignored and repairs put off until "later" can cause more damage down the road — and a higher repair bill.


Once the temperature gauge is showing "warm," it's cool to rev the engine, right?

The temperature gauge doesn't tell you the warmth of the engine; it's designed to tell you the warmth of the coolant. The engine needs to travel about 5 to 7 miles to reach its optimal temperature, where all the parts are lubricated and fully ready for action.


When working on a car, what does a torque wrench do that an ordinary wrench won't — or will any old wrench do?

Mechanics can sometimes get a little too ... enthusiastic when tightening bolts or nuts, which can lead to problems if the threads get stripped or the part is on so tightly that it can't be removed later. A torque wrench is designed to allow a certain amount of force to be used and will stop when that specification is reached.


You toss used spark plugs away without looking at them — mistake! How can spark plugs tell a mechanic about the condition of the engine?

When a mechanic pulls a spark plug from the engine, he or she can tell a great deal about how the motor is operating by looking at the condition of the electrode. If it's grey or tan, it means that things are running fine. If it's pristine, it means the cylinder isn't firing. Black deposits indicate a vacuum leak or even a blown head gasket. The color tells a story!


Engine rebuild pro tip! When it comes to compression in the cylinders, is more always better?

Cylinder compression is a measure of how tightly the air/fuel mix is squeezed between the top of the cylinder and the piston before the spark detonates the gas and drives the piston back down. Higher compression means more fuel burned and results in more power, but there is a limit. Too much compression will burn out the engine.


Use the right type of oil! When someone describes oil "weight," what are they measuring?

The oil's viscosity — how easily it pours — is measured by its "weight." A "5w30" oil has a lower viscosity rating than a "10w30" oil. High viscosity oil flows slower at low temperatures (the "W" stands for winter, and is a measure of temperature). The car's manufacturer will usually recommend the optimal weight of oil for your particular engine.


When it comes to brands of replacement parts, are all parts created equal?

It's generally better to go with original equipment manufacturer (OEM) parts because they have been designed and tested to work with your vehicle, and dependability could keep you from having to have the same repair performed down the road. Usually, when a mechanic has to replace a part, it's the labor that makes up the bulk of the cost — not the part. Replacing a head gasket can cost $1,000. The part usually costs less than $100.


When you see the temperature gauge on the rise, which of these is the worst thing you can do?

When your engine starts to overheat, it will still run, but you are running an increased risk of doing serious damage to your engine if you keep driving. If you're not in a place where you can call for help, pulling over and opening the hood can help to temporarily cool down the engine, as can running the heater. However, it's time to get your car to a mechanic.


You ignore that your car's RPMs are spiking, and there's a strange grinding sound coming from the engine. Which part(s) are you about to have repaired or replaced?

When your car's RPMs are jumping right before the automatic transmission shifts gears, if you notice that it's shifting more than usual and/or you hear a grinding sound, these are all symptoms of low transmission fluid. You'll probably want to get that checked out sooner than later.


What easy fix are you neglecting when you ignore that your engine is misfiring, horsepower is down, and there's a strong smell of fuel in the car?

Air is a vital element in the smooth operation of your car (it's the air/fuel mix that makes the car go), and all that air goes through the air filter. When the air filter gets too dirty or clogged, it can throw your entire system off kilter. The air filter is easy to examine and clean or replace, if necessary.


Engine rebuild pro tip! What's the best method of putting piston rings on the piston?

While the oil wiper ring has to be rolled on, it's recommended that you use a piston ring expansion tool to put the compression and oil control rings on the piston so as not to distort them. The expansion tool puts less stress on the rings by using uniform pressure.


Is it a mistake to add oil additives to the engine's oil supply?

Many experts believe that oil additives don't really add much to your quest to keep your engine at peak performance. It's much more important to regularly change the oil and keep it clean and at the proper level; that's what will do your engine the most good.


What does a radiator flush do?

Engine coolant loses its potency after a while, so it's a good idea to get a radiator flush done from time to time (check your owner's manual for frequency). By washing out the old antifreeze with fresh coolant, rust and scale deposits are flushed away, the water pump gets better lubrication (leading to longer life), and the mechanic can see if there are any trouble spots or leaks in the system.


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