Top mechanic Scotty Kilmer has warned petrol and diesel owners can fix their cars for “free” with a simple tip almost all owners can take advantage of.

Scotty has stressed unplugging the battery terminal would reset the car’s computer systems and could fix many issues.

This can be done on any driveway or garage and is likely to save drivers from having to pay for a mechanic to take a look at their vehicle.

Scotty made the suggestion while speaking on his YouTube channel, joking he could get “sued” for passing over too many secrets.

The leading mechanic explained: “Today I'm going to show you how you might be able to fix your car for absolutely free. Car computers are sometimes like people, they get confused.

“And what do you do with a house computer when it goes bad, you turn it off and turn it back on again.

“So here you take the battery terminal off then wait for five minutes so it can reset itself because cars are full of tiny microprocessors and this rests them to their original settings.

“Then turn the headlights on with the battery disconnected. That won’t turn the headlight on but it will empty the power in the capacitors. Then simply put the terminal back on again and make sure it's nice and tight.

“Now it might idle a little strange because the computer might have to reset the idle but you can often fix problems merely by resetting the computers.”

YouTube viewers were quick to praise Scotty’s advice with some even admitting the tip had fixed issues with their own vehicle.

@alanc6781 posted: “You can't lose, Scotty. Many of us know this trick, but not everybody. You are a good teacher. We thank you.”

@shamrockfile wrote: “Had to do this on a new Subaru, it worked.” However, one road user seemed to suggest the tip would likely not be as effective on newer models.

@jessewynne8193 added: “Unfortunately this doesn’t work on most cars after 2018 there’s a memory chip that stores codes and you will need an OBD scanner to reset.”

BookMyGarage, the leading comparison site for service and repairs, stressed it was vital road users disconnecting batteries made sure they were safe at all times.

To disconnect a battery, motorists must turn off the ignition and then find the negative battery terminal.

The nut can then be loosened and removed by twisting the screw in a counterclockwise direction.

Road users should not touch the battery again until the positive terminal has also been disconnected.