The UK's vehicle information expert HPI is urging consumers to be on their guard and pay attention to more than a vehicle's body work, but a seller's body language and facial expressions, too.
"Have you ever had that uneasy feeling that someone was lying to you but didn't know why you felt that way? It could be because you've subconsciously noticed their lying signs," explained Shane Teskey, Senior Consumer Services Manager at HPI.
"Trust your instincts. Pay close attention to body language and facial expressions. For example, look for nose-touching and mouth-covering. People touch their noses more frequently when they're lying. They're also more likely to cover their mouths.
"Of course, if you are buying online you can't look the seller in the eye or take into consideration how they are behaving so investigate the seller's history by reviewing the ratings from other buyers to ensure you're dealing with someone who will deliver the car according to the terms you are offered."
Another potential tell-tale sign of lying to look for is nodding, HPI said. When the head is nodding or shaking in contrast to what is being said, buyers should be on their guard.
"Make sure the seller isn't giving you inconsistent signals," continued Teskey.
"Does your used car seller look shifty? Perhaps constantly fidgeting? Too much fidgeting, either with their own clothing, jewellery, hair or things around them, could indicate that they are feeling uneasy and may be lying to you about the car's history."
Buyers should try to observe the level of 'mirroring' going on between themselves and the seller. When two people have a conversation, they naturally mirror the behaviour of each other, but unscrupulous sellers mirror significantly less when lying.
Finally, pay attention to the person's throat. Excessive lubrication of the throat by swallowing, throat-clearing or gulping may indicate someone is dealing with a dodgy seller.
Teskey concluded: "We always urge buyers to take along someone else with them when going to view a car. Having a second pair of eyes to check out the seller whilst you check out the bodywork will never go amiss.
"And if you don't know much about cars, try to take someone who does know a thing or two, or invest in the services of an independent vehicle inspection.
"Most importantly, don't let your heart rule your head and trust your instincts. If the car looks too good to be true, it probably is."