Should you allow a diesel engine to warm up before driving?

We decided to sit down with an expert to get the ins and outs of the warm-up and cool-down process on diesel engines.Tony is a mate of ours and he will give you the real information.Hopefully, his 30 years of experience will put some minds at ease.There are some myths to bed.Tony told us how long you should keep your engine running when you first start it and after you pull up.One way or the other, a turbo-timer is a waste of time and money.

How long should you warm up the engine on your tow rig?While they hitch the van and sort the handbrake out, we have heard some of the Grey Nomads idling away.That is a bit excessive, right?

Warm-up is a personal thing for Tony.Give the vehicle a minute or two and then go off at a steady pace.Take it steady until it warms up on the temp gauge.On modern diesels, 30 minutes of warm-up is not necessary and will cause problems with DPF-type vehicles and excessive soot build up from EGR in the intake, etc.

What is the purpose of warming-up the engine from an expert's point of view?

Tony: Warming up the vehicle allows oil to flow around the engine.The oil is too thick to lubricate when it is cold.Warming up allows all of the moving parts to get up to their correct operating temperatures and expand and contract to the correct clearances.An example of this is if you have a performance engine with forged pistons, it may make a noise when it's cold.Once they are warm and up to temperature, it goes away.It is more about not overloading the engine while it is cold.The risk of engine wear and/or engine damage increases if you give a cold engine a hard time.

Does a longer warm-up time hurt the longevity of the engine?They are burning fuel and putting hours on the engine.

Tony: Longer warm-up times on older diesel vehicles does not hurt the engine as they don't have the pollution controls of modern diesels.It takes hours on the engine to burn fuel.Diesels now have DPFs and EGR valves.excessive idling periods can cause these to operate in ways not recommended by the manufacturer.This routine can cause the intake manifolds to soot up more than normal, causing more burns and excessive fuel usage.Diesels are computer-controlled and some limit the amount of fuel delivery until the vehicle is warm enough.Taking off at a steady pace will not hurt the engine.Taking off and giving a cold engine high loads will cause excessive wear and damage.Modern diesel vehicles have better cooling systems and are designed to warm up quickly.I don't think it's worth it to let the vehicle start and idling for a minute or two.It causes a lot of noise in the caravan park.For no gains.

Is it a good idea to let your four-wheel drive sit for five minutes after pulling up?It made sense back in the day, but is there really any point in it now?

Tony: It depends on the conditions in which you are driving.Five minutes is definitely worth it if you have been working on it for a long time.If you get to the caravan park and back your van into its spot, it would be cool to just shut down, as you have done the job of the timer anyway.VNTs spin at a high rate compared to the older wastegated ones.The temperature can be reduced before the cool-down.

As a side question from cool-down, we have all seen trucks sit there idling while the driver runs into a shop, or to the loo.Is that more fuel-efficient for them to leave it idling, or is it a cool-down thing?

If you have been working hard on your vehicle and want to stop and let it cool down, or if you want the air conditioning on and the fridge on, you can allow it to sit on the side of the road.It will not hurt anything if you run the vehicle for five minutes or so.It is not necessary to drive through a town like the trucks do if you have already traveled through it.Keeping the air up to the system for brakes is one of the reasons trucks keep running.There are many different reasons for keeping the trucks running, they are vastly different to the light automotive vehicles we all drive.Leaving your car running and being more than six metres away from the vehicle can get you in trouble with the local constabulary.