Warming up: Speed vs engine speed vs load

[RobM]

I'm a big believer in the importance of correctly warming up and cooling down your engine, I'm sure most of us are. But something I'm struggling to get my head around is how to do it safely when your journey means entering a motorway within the first few minutes.

 

For instance, my journey home from work involves leaving a car park, driving roughly 1-mile before entering a major dual carriageway which becomes a motorway within a couple of miles. Therefore I'm at 50-70mph within a few minutes of starting the car, which doesn't feel right.

 

What I can't get my head around is what exactly is going to do the most damage. Is engine speed the concern (e.g. RPM) or engine load (e.g. acceleration, change in speed). If I let the speed increase carefully (avoiding too hard acceleration) to the road-speed but then maintain it at a fairly constant speed, therefore keeping the RPM fairly steady (around 2-2.5k RPM in my CR VRS), is this the most 'lightweight' option? Or is engine speed alone going to do damage on a cold engine and I need to keep the speed down for longer?

 

I know some of you lot are far wiser than I am on subjects like this, so I hope you can help me make sense of it

 

Thanks.

[Plantman]

IMO engine speed is the best thing to keep down until the engine is up to temp.

 

Keep the revs down for as long as it takes by keeping in the highest gear without labouring the engine.

 

At high road speeds the engine soon warms up on a motorway. 

 

The wear is caused by a cold engine and cold thicker oil which doesn't circulate quickly or efficiently enough, so you get a friction wear scenario. Less high revs during warm up will limit this.

 

Overall, it's a modern engine so worry less and enjoy. Providing your not starting and getting out there on the red line in the rev band you wont be causing any issues

Edited 17 March, 2014 by Plantman

[BlueVRSTom]

This is not gospel however.

On a cold engine ( esp tdi ) use gentle acceleration no more than 1/4 and do not allow rev counter to go above 2k when accelerating.

Once your in 6th gear again don't go higher than 2k but you should be able to reach 70-75mph as soon as the temp gauge has moved onto the first bar then you can increase rpm and speed up to 2.5k max.

Then as soon as engine is fully warm then you can use maximum acceleration and speed and rpm where necessary etc.

What I've discussed is very important on a PD engine but not as on a CR.

Good luck and don't worry.

Gentle acceleration, don't thrash it. It's revs that matter now speed

[stever750]

The oil isn't thick when cold, not in the UK anyway, that's the whole point of using 5w30 or 40. It maintains the same viscosity at the ends of the temp range. The issue us thermal expansion, too much heat too quick will create more stress. I'm pretty sure though you could drive hard from cold and not damage a modern engine.

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[Guest]

I'm going to cop some flack but you did ask after all...

There's always oil flowing in your engine, assuming there's sufficient oil and the oil pump and related components are functioning as intended.

Yes hot oil will be less viscous but if you use the correct grade of oil for the weather conditions you will be fine.

Wear most often talked about is cylinder/piston friction and is a function of thermal expansion, aluminium pistons expand faster than the surrounding cast iron cylinders causing a tighter than ideal fit until the engine is at a uniform temperature.

When people talk about waiting for the engine/oil to warm up to reach all upper cylinder components it's just nonsense from a bygone age.

There are of course special circumstances when engines require to be up to operational temp before being asked for maximum power eg aviation piston engines, my field.

You don't want an aeroplane engine failure, especially at take off.

So for a road going vehicle the most sympathetic treatment you can give your engine is to drive without excessive engine speed and avoid labouring the engine when the pistons will be pushed hard against the cylinder walls.

So if it's a diesel it's very easy to tread overly cautiously on the loud pedal, drive briskly without racing or labouring and don't worry.

An experienced motorist should know when their engine is revving freely in the happy middle rev range.

[RobM]

I knew I'd come to the right place to ask, thank you all very much  :sun:

 

It's good to know I'm safe and doing the right thing, but it's even more useful to know the detail behind it, so thank you all!

[brad1.8T]

2-2.5k rpm cruising wouldn't worry me as much as having to use full throttle on the merge

[Phil-E]

I wouldn't worry about it.

 

In a DSG it's very easy to accelerate gently and have the box change up early.

 

Phil

[nick74]

When was the last time you heard of someone having to replace the diesel engine in their car because it was worn? Most diesel cars and small vans go to their final resting place in the scrapyard with crashed/corroded bodywork, expensively failed ancilary components, trashed interiors, but very very rarely do they have any appreciable engine wear. My philosophy has always been to change the oil & filters regularly, then drive it how you like :-) I never thrash engines in the first few seconds of running, but equally never intentionally limit the revs when driving from cold. I tend to keep my diesels to 150-200k and have never experienced any signs of engine wear, and some have noticeably improved as the miles piled on.

[Anddenton]

To be fair most of the warm up/warm down is to protect the turbo rather than the engine itself.

[RobM]

That's my thoughts to be honest, I understand where Phil is coming from entirely, but it's the more fragile components that I worry about as well, the turbo being a key one.

[Phil-E]

That's my thoughts to be honest, I understand where Phil is coming from entirely, but it's the more fragile components that I worry about as well, the turbo being a key one.

 

Shouldn't need to worry about that either really.

 

I know in mine if I'm light on the throttle the gearbox changes at 2000rpm and on light throttle the turbo will barely be working.

 

Phil

[RobM]

Absolutely, which is the point really, being gentle generally protects the engine as well as other bits like the turbo as nothing is under stress. Getting my head around what causes the most stress was the aim of the question.

It's all to be safe rather than sorry really, I was never bothered when I had company cars but it's different when is your own money! Company cars don't need warming up...

[Phil-E]

Yeah the main issue is having the turbo working hard with cold oil being pumped to it.

 

You get a big heat difference between the turbo and the rest of the engine etc.

 

Likewise when cooling down it's not good to have just worked the turbo hard then stop.

 

Otherwise just drive steady and be sure to give it a good thrash now and then once it's warmed up.

 

Phil