Engine wear at different Speeds

[Andehh]

I hear it a lot that cars at motorway speeds (70 – 80mph) are sitting in their idle range for reducing engine wear etc. How much of this is true? For example how many miles of town/city/stop start driving equates to how many miles sitting on the motorway at cruising speed?

Does it really make a big difference, or is it old wives tails? What are the components that feel the brunt of these different journeys?

I am curious as I have gone from 7-10 miles of stop start traffic, engine on engine off at various stops to a 29 miles of pure dual/motorway 70-75mph driving.

[kambites]

I would imagine, for a warm engine, that you get pretty much the same amount of engine wear per revolution of the engine, regardless of type of driving. Short trips are worse (more time running cold) and driving in lower gears is worse (more revolutions of the engine).

Whether modern engines wear significantly at all is debatable.

[Ozzie Osmond]

With modern engine manufacture and modern fully synthetic oils engine wear is virtually non-existent. Pretty much all the wear that does happen takes place in the first few minutes (some would say seconds) after a cold start.

Certainly at cruising speeds engine wear is a thing of the past, pretty much irrespective of rpm.

[Mattt]

I know Porsches log the engine hours in the software, so you can compare against the mileage to see the life the car has lead.

[Classic Grad 98]

I've always assumed that variations in engine speeds were more likely to accelerate wear than if the engine is ran at a contant speed. Industrial engines which run at a fixed RPM have huge service lives.
I don't think running at a particularly low RPM will save engine wear, assuming the same gear is used. Using a lower gear will obviously increase the number of engine revolutions/piston strokes for a given distance driven though.
I expect engine wear will be greater in an engine which is ran consistently at much above it's power band- probably valvetrain wear

[Andehh]

So with the likes of the turbo (my next big bill I imagine, diesel at 100k miles atm), how would it be effected? Would keeping the engine speeds below the kick in for it benefit, or is that insignificant in the big scheme of things?

[300bhp/ton]

Andehh said:

I hear it a lot that cars at motorway speeds (70 – 80mph) are sitting in their idle range for reducing engine wear etc. How much of this is true? For example how many miles of town/city/stop start driving equates to how many miles sitting on the motorway at cruising speed?

Does it really make a big difference, or is it old wives tails? What are the components that feel the brunt of these different journeys?

I am curious as I have gone from 7-10 miles of stop start traffic, engine on engine off at various stops to a 29 miles of pure dual/motorway 70-75mph driving.

Does it really matter?

Your profile says you own this:


Are you really planning on keeping it past 300,000 or 400,000 miles?

If not why care?

And even if it did matter, are you going to really change how you drive?

[alfa pint]

Don't expect anything significant increase in engine wear at low revs, provided that the engine isn't labouring. Similarily, high revs won't make it dramatically worse, provided it's below the red line for short periods of time i.e. changing up, not thrashing it and that the oil is warm.

[kambites]

Why would labouring increase engine wear? I can see that it causes problems, but I can't see why wear would be one of them.

[Classic Grad 98]

Andehh said:

So with the likes of the turbo (my next big bill I imagine, diesel at 100k miles atm), how would it be effected? Would keeping the engine speeds below the kick in for it benefit, or is that insignificant in the big scheme of things?

I think a turbo is unlikely to benefit from being ran at particularly low engine speeds, so long as the oil pressure is okay and a warmup/cooldown process is used.

[kambites]

Ah, turbos are a different matter because they don't rotate at the same speed as the rest of the engine. I suppose keeping it off boost as much as possible is best for the turbo, since it'll be spinning slowly, although I'm only guessing.

[Andehh]

With doing around 34-35k a year from now on, I want to make sure that i'm treating the car as gently as possible. Just wanted to make sure i knew as much as I could.

House, 4 winter tyres, 4 summer tyres, paying back a golden hand shake have made it a very very expensive summer!


edit; Turbo is the main area of my focus. Skoda replaced all 4 injectors FOC for me and passed off posts on Brisokda, the turbo is usually the next big bill around 100k +. (though these could just be witterings of paranoia...)

Edited by Andehh on Tuesday 8th November 11:28

[kambites]

For that kind of mileage, I suppose the most important thing is to make sure you change the oil on mileage not just age.

[falkster]

kambites said:

Ah, turbos are a different matter because they don't rotate at the same speed as the rest of the engine. I suppose keeping it off boost as much as possible is best for the turbo, since it'll be spinning slowly, although I'm only guessing.

I think you'd need to keep a turbo separate in this instance other than to preserve its life the warm up and cool down procedure must be followed. If you were that concerned about turbo wear to keep it off boost I think a lada samara would have been a better buy.

[Andehh]

haha, not that concerned, more a curiosity!

Bought the car (been a brilliant car...) was about 2 years ago, based on me doing far less driving. New job came up that i couldn't turn down so that's boosted my mileage up considerably. I'm just relieved I went for the diesel and not the petrol like I was leaning to at the time!

[Ozzie Osmond]

Andehh said:

So with the likes of the turbo (my next big bill I imagine, diesel at 100k miles atm), how would it be effected? Would keeping the engine speeds below the kick in for it benefit, or is that insignificant in the big scheme of things?

I suspect jumping hard on the throttle pedal of a turbo car may cause more engine wear but it's even more likely to eat the transmission!

And an engine chipped for more grunt will certainly threaten engine life and especially the transmission if that grunt is used.