Is it worth warming up car engines before driving?

Warming up car engines

Drivers of a certain age will doubtless remember their fathers heading out before trips to ‘warm the car up’. Cars have come a long way in the last 20 years, let alone the last 40. But some people still believe a car’s engine needs warming up. We investigate how right they are and look at how leaving a car to warm up could cost more than you think.

Why do we think cars need warming up?

Cars used to employ something called a carburettor to regulate the fuel-air mixture that engines burn. Although a carburettor is a relatively simple bit of kit, its job is quite a complex one. It must control the fuel-air mix being fed to the engine at all speeds and temperatures. To do this properly and ensure the engine runs cleanly at all speeds, a carburettor needs to be warm. That’s why your dad or grandad would have been keen to warm his car up before driving.

Why don’t modern cars need warming up?

During the 1990s carburettors were replaced with fuel injection. As electronic technology has become increasingly sophisticated, so fuel injection has got better at mixing exactly the right amount of fuel and air for temperature conditions and driver requirements. And unlike a carburettor it’s as efficient at doing this when it’s cold as when it’s hot.

That’s not to say you can cane it from the off!

We all need a bit of time to get used to what we’re doing. Whether that’s doing an exercise class or even driving itself, we’re better when we’ve been doing it for a few minutes. The modern engine doesn’t need warming up in the traditional sense of the word. But the warmer oil is, the better it’ll do its job of lubricating the metal parts inside an engine. And it takes a few minutes for the oil to reach the right temperature. That said, your engine will reach its best operating temperature quicker if it’s being driven normally for a few miles and not sitting in the road idling.

Why else should you take it gently on a cold engine?

Experts agree that leaving a modern engine to warm up by idling achieves little other than burning fuel without getting anywhere. But the colder an engine is, the more fuel there is in the fuel-air mixture. That means driving a cold engine hard is simply using more fuel. What’s more, when an engine is cold, the catalytic converter in the exhaust isn’t at its most efficient so your car is likely to be pumping out more harmful emissions.

Why warming your car up could cost more than you think

Warming up car engines

For most of us, warming up a car means bringing the inside up to a habitable temperature. And it’s not unheard of for drivers to go out, start the car, then go back inside to finish their coffee, put the dishwasher on and pack their work stuff. But if someone takes advantage and steals their car while they’re doing this, their car insurance won’t pay out. The Financial Ombudsman states: “Most motor insurance policies contain an exclusion clause (or a condition) that effectively removes the cover for theft, attempted theft, and malicious damage if the ignition keys were left in or on the car.” Warming a car up? It’s really not worth the effort.

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Mandy Weston

Mandy is an ex-mechanic, with 22 years’ experience in the motor industry. As an in-house motoring expert, Mandy is the go-to woman for any relevant questions that our customers have; both garages and drivers. From specific problems with your car to general maintenance, Mandy is a reliable source of information and advice. Her passion for motoring is a huge factor to her success and the huge wealth of knowledge that she has. She now uses her remarkable grasp of the industry to write regular content for our readers to help drivers understand their car better, avoid being ripped off by garages and save money on their motoring requirements.