Motoring is full of “golden rules” everyone has heard at some point — from an uncle, a mechanic, a friend, or an internet forum from 15 years ago. The problem? Many of them were true… once. Today, they can do more harm than good.
Here are the myths nobody really explains properly — but which can seriously affect your car and your wallet.
MYTH 1: “A diesel engine needs long warm-up time while idling”
One of the most deeply rooted beliefs.
👉 Truth:
Modern diesel engines should NOT be left idling to “warm up” for several minutes.
Why?
- engines warm up more efficiently while driving
- long idling increases fuel consumption
- can contribute to clogging systems (e.g. DPF filter)
👉 What to do instead:
Start the engine → wait 20–30 seconds → drive gently.
MYTH 2: “Always fill up the tank — it saves money”
Sounds logical, but…
👉 Truth:
Not always.
- city driving → extra fuel weight increases consumption
- short trips → you don’t benefit from a full tank
👉 When it makes sense:
- long trips
- driving in areas with few fuel stations
- traveling abroad
MYTH 3: “Manual cars always use less fuel than automatics”
Used to be true.
Today: ❌ not necessarily.
👉 Truth:
Modern automatic transmissions:
- shift faster than humans
- optimize gear ratios better
- are often more fuel-efficient in cities
👉 In traffic, automatics usually win.
MYTH 4: “The slower you drive, the less fuel you use”
Sounds reasonable… but only to a point.
👉 Truth:
The most efficient speed is usually:
- around 70–90 km/h (depending on the car)
👉 Driving:
- too slow → inefficient engine operation
- too fast → aerodynamic drag increases dramatically
MYTH 5: “Neutral gear saves fuel when coasting”
👉 Truth:
In modern cars, it’s actually the opposite.
- in gear (with no throttle) → fuel consumption can drop to 0
- in neutral → the engine must still burn fuel to stay running
👉 So: neutral = more fuel use in most cases.
MYTH 6: “More expensive fuel is always better”
👉 Truth:
If your car manufacturer doesn’t require premium fuel:
- you won’t feel any difference
- you’re just overpaying
👉 Exception:
- high-performance / sports engines
MYTH 7: “New cars don’t break down”
👉 Truth:
They do — just differently.
- more electronics
- more expensive repairs
- more complex systems
👉 Old cars: break more often but cheaper
👉 New cars: break less often but more expensive
MYTH 8: “Short trips don’t harm the car”
👉 Truth:
One of the worst habits.
- engine doesn’t reach optimal temperature
- oil doesn’t work efficiently
- faster wear of components
👉 Diesels suffer the most.
MYTH 9: “Oil change every 20–30k km is enough”
👉 Truth:
That’s marketing, not engineering reality.
- safe interval: 10–15k km
- longer intervals = higher engine wear
MYTH 10: “Bigger engine means higher fuel consumption”
👉 Truth:
It depends.
- small engine under heavy load = high consumption
- larger engine running smoothly = sometimes more efficient
👉 Downsizing isn’t always the winner.
🧠 Things Almost Nobody Mentions
👉 air conditioning can increase fuel consumption by up to ~10–15%
👉 driving with open windows at high speed uses more fuel than AC
👉 underinflated tires = up to +5–10% fuel consumption
👉 roof racks = seriously harm aerodynamics
👉 driving on low fuel damages the fuel system
The fuel pump is cooled by fuel — constantly driving on “empty” makes it wear out faster.
👉 extra weight in the trunk = higher fuel consumption, even if you don’t feel it
Carrying an unnecessary 30–50 kg for weeks or months really adds up.
👉 short trips wear out your car more than long drives
The engine and oil don’t reach optimal temperature → more wear and tear.
👉 cruise control doesn’t always save fuel
On flat roads — yes.
On hilly terrain — often the opposite, because the car tries too hard to maintain speed.
👉 driving too gently isn’t always good either
Constantly driving at very low RPM can lead to carbon buildup and engine issues.
👉 your driving style has the biggest impact on fuel consumption
Not the engine, not the brand — the driver.
The difference between aggressive and smooth driving can reach 30–40%.
🚗 Summary
Most “car truths” today are either outdated or half-truths. And following them blindly can cost you:
- more fuel
- faster wear and tear
- unnecessary expenses
Sometimes the best thing you can do is forget what you’ve heard… and look at driving with fresh eyes.
