Low speed, high gear (lugging the engine)
It’s a common mistake to not downshift when you want to accelerate. Using the low-end torque to continue the progress is okay, but not shifting down when you want to accelerate is bad. It damages the clutch, the gearbox, and even while doing so, you’re still stuck looking for power.
Also, unless your car’s manufacturer says very clearly in the owner’s manual, do not take off in the second gear. It might have enough torque to pull you through, but that’s not the point. In the process it can overwork the clutch. Which is not a good thing.
Rule of thumb: If you want to accelerate and are not in the powerband, drop down a gear and off you go!
Another problem is that some people just continue driving in a higher gear, at a lower rpm. And when they sense a loss of power, they ride the clutch to overcome that. Don’t be that fool. Ever.
Downshifting into a lower gear at high speed
On the other hand, every gear is optimised to be used at a maximum speed. Exceeding this, irrespective of whatever excuse you have, is going to damage the gearbox. Switching to a lower gear while doing a high speed will have a bad effect on the clutch as well.
And worse of it all, it can cause you to lock the wheels and come to a grinding halt and subjecting yourself to being rear-ended. in case of a rear wheel drive car, it can cause a spin, which in most cases is going to end up with you having a car that’s maybe narrower and shorter than what it was two minutes ago.
Not stopping for speed-breakers
Speed-breakers are there for a reason, and that is to keep a check on the automobiles’ speed. Now if you want to defy their existence and subject other road users to your buffoonery, that’s up to you. But driving fast over these has an adverse effect on the suspension, too. While the cars can take this much of abuse but the wear and tear goes up, as well. A harder hit and you can be looking at irregular wear on tyres, an out of alignment wheel, etc.
Missing scheduled maintenance
Zero-maintenance is a myth, especially if you’re looking at running an everyday vehicle. Bit and bobs need tightening, some lubrication, and various fluids need to be replaced at regular intervals. And these things are vital because an unhealthy car can be very dangerous to drive as well. For instance, a mis-aligned wheel means your car might swerve more to one direction when it’s supposed to go straight. Or it will overheat (and maybe even cease) under increased load.
Driving at high speeds at low tyre pressure
Optimum tyre pressures are clearly indicated by every car/tyre manufacturer. And unless you’re doing rock-climbing or drag-racing, just stick to the mentioned tyre pressures. Failing to do so can be fatal.
Think about it this way. You are doing highway speeds on a more taxing surface like concrete, and the tyre pressure is way below the prescribed one. The tyre runs hot, bursts, you lose control of the car, and irrespective of how well-versed you are with it, there’s a good chance that it won’t end well.
Why subject yourself and your loved ones (or whoever the other occupants are) to such atrocity when all it takes is a five-minute stop at one of the petrol pumps. Also, keep in mind that if you’re getting air refilled from one of the big compressor guys (the ones who refill trucks’ and buses’ tyres), check the pressure with your gauge — theirs is generally way off.