Do Not Fall For These 15 Car Myths

Common Car Myths That You Should Not Fall For

Every car owner wants their vehicle to perform well and last long which is why most of us often fall for myths that seem to have little or no basis of truth. But since we hear it from enough people or in misleading advertisements, we tend to believe them to be true and even start practicing those myths. Most myths are too good to be true while some have a scientific explanation as proof, but the real truth is often hidden in the fine print. So we’re here to set the records straight and tell you why you should stop believing certain rumors, especially the ones that can harm your vehicle. 

Here Are The 15 Car Myths Debunked

Myth - Warm Up Your Engine Before Driving In Cold Weather

Truth - This is a common myth especially heard in cold climate regions. However, it is not true since idling your engine in the cold before you set off is not going to be beneficial. The idea behind the myth is that idling the vehicle before driving will heat the engine and a warmer engine will perform better. Although idling the engine actually creates the least amount of energy and therefore generates the least amount of heat. The best practice is to start your engine in the cold and drive away. 

Myth - Regular Gas Can Ruin Your Performance Engine And Premium Gas Can Increase Performance In Your Non-Premium Vehicle

Truth - This is a fairly common misconception that regular fuel is bad for performance engines or that you should only use premium fuel even in your non-premium car. The only difference between regular and premium gas is the octane rating. Premium gas has a higher octane rating which essentially means that it ignites at higher pressures and temperatures compared to lower octane fuel. It is best to stick to the manufacturer's requirements for fuel type which can be found in the vehicle manual or behind the gas tank cap. 
There is a great difference between requirements and recommendations. If the vehicle manufacturer requires the use of premium fuel then you need to add premium fuel only and cannot switch to regular. Wheres if the manufacturer recommends the use of premium then you can still use regular fuel. So unless your vehicle manufacturer requires the use of premium fuel in your engine, you can easily use regular without issues. Most manufacturers give different horsepower and fuel economy numbers for regular and premium fuel. So you might get less horsepower when on regular fuel or the fuel economy may trickle down a bit but won’t affect the engine or its life. However, many experiments show that the difference in performance between premium and regular is very little to actually see real-world benefits. Also if your vehicle manufacturer does not recommend the use of premium gas, then you absolutely won’t see any difference and it will essentially be a waste of money opting for premium. 

Myth - It Is Better For Fuel Economy To Let The Engine Idle Than Turning It On And Off

Truth - This is an old saying that was applicable to carburetted engines but does not hold true on modern fuel-injected engines. Carburetors depend on airflow for fuel delivery. So on a carburetted engine, letting the car idle at a stop limits the amount of fuel entering the engine since there is little to no airflow. But when you start a carburetor engine, a larger portion of fuel is required to get the engine running since the airflow is limited. Whereas, on fuel-injected engines, the amount of fuel supplied is closely monitored whether the engine is idling or starting. So to cut off fuel completely at a stop would be the best option as it does not consume any fuel at all. And when you do start it, the fuel supplied will be minimal. Many modern cars have a feature that automatically shuts off the engine when the vehicle stops and starts it back up again when you press the gas pedal. This is done not only to save fuel but also to reduce exhaust emissions.

Myth - Manual Transmission Offers Better Fuel Economy

Truth - Back when automatic transmission technology was new, manual transmission was the clear choice in terms of fuel efficiency. But modern automatic transmissions have evolved from their predecessors and new automatic trans can actually be more fuel-efficient than manual transmissions. Most modern automatic transmissions have more gear ratios than standard manuals while some even have infinite gear ratios, like continuously variable transmissions. More gear ratios mean smaller engine rev ranges. Lower engine revs consume less gasoline and therefore save fuel. You may even find that the vehicle EPA ratings for newer models with auto transmission have better mileage compared to manual transmission variants. So this myth was true about 20 years ago, but now the story is quite different. 

Myth - Using The AC While Driving Will Affect Fuel Consumption

Truth - Most people argue that pulling the windows down is better for fuel economy than using air conditioning. Now there are two sides to this story and both are equally true. There have been many experiments done on different vehicle types at different speeds and driving conditions. Most of these experiments prove that the speed of the vehicles plays an important role in fuel consumption. At speeds below 80 km/h, the drag created by pulling the windows down was lower than the energy consumed by the AC. So you would save more fuel if you switched off the AC and pulled the windows down in short commutes within the city. While driving above 80 km/h, using AC is better than rolled down windows because the drag created by lowered windows was harder for the vehicle to overcome, and hence using the AC would prove more fuel-efficient. 

Unless you have a major problem with the AC system, you will likely not get tremendous fuel savings from avoiding AC and opening the windows. If you do notice issues with the system, here's how you can diagnose your AC compressor

Myth - Filling Up Gas In The Morning Will Yield More Gas Than Filling In The Afternoon

Truth - This myth has probably destroyed many morning sleeps and schedules. No matter its popularity, this myth is not true. The reason this myth is often believed to be true is that fuel is denser at colder temperatures and so filling up early in the morning will get you more fuel for the same price. Firstly, the fuel tank that stores the fuel at the station is underground and relatively well insulated which means the fuel temperature is unchanged whether it’s colder or warmer outside. Secondly, a slight change in density is not going to increase the amount of fuel and the amount of energy the fuel can burn is going to stay the same. So you won’t get any benefits whether you fill up in the morning or afternoon.

Myth - You Can Add Special Additives To The Engine Oil To Increase Engine Performance, Reduce Fuel Consumption Or Make The Engine Last Longer

Truth - In reality, if such additives do exist, they are most probably already part of the engine oil recommended by the manufacturer. And if other magical additives could have such benefits, the vehicle and oil manufacturers would add them to the factory as this would get them better EPA ratings and be good for the environment. So don’t fall for clever marketing and false advertisements and always research any products that claim to do wonders or sound too good to be true. 

Myth - You Can Add Thicker Engine Oil If your Engine Is Burning Oil

Truth - You should never change the engine oil grade. This idea of adding thicker engine oil arose back in the day when people used to add thicker engine oil to prevent the engine from burning oil. This held true then because the engines then were not as advanced as today’s engines. Modern engines are built with tight tolerances and have sophisticated technology like variable valve timing, that relies on oil pressure for proper functioning. If you add thicker oil than what's recommended, you risk the engine running dry on startup. The engine experiences the majority of its wear during startup when the lubricating oil is scarce between various parts of the engine. If you add a thicker oil, at lower temperatures the engine will take longer to circulate this oil and might not even flow into tighter orifices. This can be extremely detrimental to the engine. So you should never deviate from the engine oil grade recommended by the manufacturer for any reason. 

Myth - You Need To Change The Engine Oil Every 3000 Miles / 5000 Km

Truth - Unless you have an extremely old vehicle (30+ yo) with a high-mileage engine, you do not need to replace the oil every 5000 km. Most modern vehicles can go without an oil change for up to 15,000 km. The oil change interval actually depends on many factors such as the vehicle, driving condition and location and also the type of oil used. Conventional oil needs to be replaced at about 8000 to 10,000 km. Synthetic oils can last longer than conventional oils and so have longer replacement intervals. Semi-synthetic or synthetic blend and fully-synthetic oils have change intervals ranging from 12,000 to 15,000 km. This number can be extended even further if you are only driving on highways. This is because highway driving does not deteriorate engine oil as much as stop-and-go traffic common to city driving. 

However, you need to change the oil every year regardless of the mileage because the oil breaks down over time and so needs to be replaced especially organic oils. Also, remember to change the oil filter during every oil change.

Myth - You Can Adjust The Tire Pressure To Suit The Driving Conditions

Truth - For everyday commuting and highway driving the only recommendation is to stick to the manufacturer’s tire pressure specifications. In older cars, it was common practice to reduce the pressure by a few psi to get better ride comfort due to the softer tires. But this is actually very unsafe because running on underinflated tires will increase their wear, fuel consumption and reduce the safety and handling performance of the vehicle. The only time you should underinflate tires is when you are off-roading on sand or rocky terrain. Here the increased contact area will give better traction. Apart from this, there is no other reason you should underinflate tires. 

Another common malpractice is to overinflate the tires to get better fuel economy due to the lowered rolling resistance. This can not only reduce safety, due to the smaller contact patch, it also makes the suspension work harder making it more susceptible to failure and increasing tire wear along with worse handling and comfort. 

So you should never deviate from the manufacturer’s recommended tire pressure and regularly check the tire pressure to make sure it’s within spec. Always check the pressure when cold to get the absolute reading. Do not over or under-inflate tires.

Myth - Transmission With Lifetime Fluid Does Not Need To Be Replaced At All

Truth - This is not true. Vehicles with sealed transmissions and lifetime ATF also need transmission fluid replaced after about 100,000 km. No fluid can last forever. The lifetime guarantee is for the lifetime of the transmission which if it fails after the warranty period expires, it is going to cost you a lot to repair. Which may have been prevented with a simple fluid replacement. if you have such a transmission with more than 100,000 km, consider replacing the fluid. However, replacing the fluid at very high mileage can also be harmful. Find out the truth in the next debunked myth. 

Myth - Changing The Transmission Fluid In A High Mileage Car Can Ruin The Transmission

Truth - Many people with automatic transmission have complained that after a fluid change or flush, they experienced gear slipping, inability to change gears, and in some cases complete transmission failure. However, this only happens when the first fluid change occurs at very high mileages (250,000+ km). This happens because the fluid gets extremely dirty, burnt, turns black, and gets filled with crud and metal debris from the transmission. But surprisingly that is what’s keeping the transmission from slipping. If that dirty fluid was to be replaced with clean fluid at this point, the clutch pack would lose any friction from suspended clutch material within the dirty fluid to be able to work properly and hence starts to slip and in worse cases ceases completely. The right way to fix such a high-mileage transmission is a complete refurbishment where it is taken apart and all worn parts are restored. This procedure obviously costs a lot and most people aren’t willing to shell out so much for an old transmission. So the only thing to do at this point is to leave the transmission alone and let it run as long as possible. 

Nevertheless, you can completely avoid such a situation by regularly replacing the transmission fluid with the right type of fluid recommended by the manufacturer. Most vehicle manufacturers recommend replacing the ATF every 50,000 to 80,000 km. The replacement interval may vary from vehicle to vehicle and can be found in the owner’s manual. Although if your vehicle has a sealed transmission, the vehicle manual might not have any information on this in which case you can replace the fluid once it reaches 100,000 km. 

if your transmission fluid is black with visible metal debris, then it would be the safer option to avoid fluid change. You can consult your mechanic for more information. But if you have followed regular maintenance and fluid changes in your transmission, then you can replace the fluid without any issues. 

Also, remember to always use the right type of transmission fluid. Do not change the fluid type or there can be serious problems in the system. In auto transmissions, the fluid is essential for driving the entire transmission. It flows through orifices, computer modules, and valves that control the entire movement of the system. So you do not want to mess with the system by changing the fluid type. If you have a CVT then only add CVT fluid and nothing else. Here are some of the other essential fluids in your car that need to be replaced regularly

Myth - Products That Can Increase Fuel Efficiency Or Engine Performance

Truth - Many products in the market claim to increase the fuel economy or engine performance or both by either adding a bolt-on part to your car or through some electronic gadget you can install. You might have seen ads on late-night TV that feature paid testimonials to make you think they actually work. The truth is that all such components are a big rip-off designed to take your money and nothing else. Some even provide scientific reasoning behind their madness to justify the expense but they are just marketing tactics and have no real-world benefits. If such technologies did exist, the manufacturers would be intent on adding them to the vehicle to make their vehicles greener instead of spending billions on research to reduce emissions and increase fuel economy. Modern engines are already as fuel-efficient as can be, so we insist you stay away from such fiction. Things like magnetic fuel sender, USB fuel-saving devices, etc. If you want actual products that increase engine performance and fuel economy you refer to this article on easy-to-do and affordable engine upgrades.

Myth - You Should Only Use Premium Fuel In Older Vehicles

Truth - Older engines with more than 300,000 km that have not been cleaned or refurbished, have a lot of carbon build-up. This build-up can reduce the combustion chamber clearance volume and increase the compression ratio. If you were to use regular fuel, there is a likelihood of knock or pre-ignition. Which if sustained over long periods can damage your engine. So engines with very high mileage can actually benefit from high-octane or premium fuel. As this fuel is less volatile, it can prevent knocking and therefore benefits the engine in the long run. You may also notice a slight increase in fuel economy since the engine runs better. However, you could clean up the engine and remove the carbon buildup or continue using premium fuel as the difference, in the long run, is going to be the same and you may even get better fuel economy. 

Myth - Don’t Use Mobile Phones When Filling Up Gas At The Station

Truth - This is false. There have been no recorded incidents of fire from using the mobile phone when filling up gas. This myth started around the time when phones became common and gas stations started plastering “do not use cell phone” warning signs everywhere. In older mobile phones with exposed antennas, there could have been some chance of a spark that could ignite the airborne fuel vapours exiting the fuel tank, but not in modern vehicles and modern mobile phones with concealed antennas lines and sophisticated fuel storage systems. However, do remember to turn off the engine as that can actually cause an explosion.


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John Framigllia
Technical Writer
Our technical writer is known for simplifying automotive parts and services. Intuitive with various vehicles and manufacturers, he knows how to simplify complicated problems.