PHEV's engine wear?
Discussion
I was recently looking at a Mercedes GLC 300 de plug in hybrid which has a largish battery good for a 60-70 mile electric only range.
My question is this - I was always brought up on the assumption that to maximise longevity you should, firstly, warm up the engine and, secondly, constant running was better than continual stop / start.
I'm not an engineer but it seems that hybrids go against both these principles and, in particular the engine only fires up under heavy load.
Am I wrong?
My question is this - I was always brought up on the assumption that to maximise longevity you should, firstly, warm up the engine and, secondly, constant running was better than continual stop / start.
I'm not an engineer but it seems that hybrids go against both these principles and, in particular the engine only fires up under heavy load.
Am I wrong?
I don't think you're that wrong. In colder times, I see many EV's join the motorway and the ICE fires up as evidenced by the condensation from the exhaust. If you had a pure ICE car, the engine would slowly warm up on your drive to the motorway and it would be up to temp.
Someone will probably come along and say that the engineers have thought about this and warmed the engine up somewhat, but have they?
Someone will probably come along and say that the engineers have thought about this and warmed the engine up somewhat, but have they?
No, not wrong. I have always avoided starting a car's IC engine if it isn't going to be run at least until the water temperature is up to normal. My family car is a PHEV with a range on battery of no more than 30 miles, but whilst that suits my main use of local trips, occasionally, like one day this week when I parked for a couple of hours in full sun, the petrol engine started as soon as I pressed the START button regardless of adequate battery capacity. This was because, I believe, the traction battery was at a temperature near its ideal maximum for heavy current drain so the air conditioning system was invoked to cool the cells whilst driving the car with minimum EV demand to ease the load on the traction battery until it had been cooled sufficiently. The journey I was about to take was <7 miles so only just enough to thoroughly warm the petrol engine. By selecting a mode in which the IC engine is more or less always used I was able to drive the distance on petrol. It is probable that the car's computer would have ensured this anyway, but me being a bit of a nerd in these matters, I made certain!
I realise that the manufacturers must be aware of this anomaly but judge that the petrol engine is not run for the entire duration of the service intervals of 12k miles so that oil degradation from condensation of cold starts is minimal before the oil is replaced.
I realise that the manufacturers must be aware of this anomaly but judge that the petrol engine is not run for the entire duration of the service intervals of 12k miles so that oil degradation from condensation of cold starts is minimal before the oil is replaced.
motco said:
I realise that the manufacturers must be aware of this anomaly but judge that the petrol engine is not run for the entire duration of the service intervals of 12k miles so that oil degradation from condensation of cold starts is minimal before the oil is replaced.
That's an interesting point - i.e. as the batteries in PHEV's get bigger, I assume that means the petrol engine fires up less and less....but I am sure the manufacturers don't change the service intervals.A few points:
Modern synthetic oils are vastly better at low temperatures than even older synthetics, let alone mineral oils.
PHEVs are designed to fire the engine up while there's still a fair bit of charge in the battery, meaning a large chunk of the total system torque after ICE start-up is still being provided by the electric motor. Hence the load on the ICE is initially very low.
The "constant running is better than constant stop-start" is a bit of an oversimplification. The real engine killer is too many cold starts, although obviously with a warm start on a conventional engine there will be a very brief period of low oil pressure. However, to counter the second point, many (maybe even all?) hybrids have electric oil pumps which fire up to get oil flowing before the engine itself is started.
Realistically for any given total mileage, the lower load on the ICE component of a hybrid will have more of a positive effect on its longevity than the negative effect of the extra stops and starts.
Modern synthetic oils are vastly better at low temperatures than even older synthetics, let alone mineral oils.
PHEVs are designed to fire the engine up while there's still a fair bit of charge in the battery, meaning a large chunk of the total system torque after ICE start-up is still being provided by the electric motor. Hence the load on the ICE is initially very low.
The "constant running is better than constant stop-start" is a bit of an oversimplification. The real engine killer is too many cold starts, although obviously with a warm start on a conventional engine there will be a very brief period of low oil pressure. However, to counter the second point, many (maybe even all?) hybrids have electric oil pumps which fire up to get oil flowing before the engine itself is started.
Realistically for any given total mileage, the lower load on the ICE component of a hybrid will have more of a positive effect on its longevity than the negative effect of the extra stops and starts.
I can't comment on any PHEV cars but my old Lexus RX400h covered 180k miles when I passed it on. The battery was fine and the engine sounded perfect and never burnt any oil. It is still in daily use as far as I know.
I would not be worrying at all, you need to worry about the starin the extra weight puts on the suspension if anything.
I would not be worrying at all, you need to worry about the starin the extra weight puts on the suspension if anything.
My PHEV always starts in Electric only mode and apart from a 150 mile round trip last weekend all my journeys over the past couple of weeks have been short and entirely on battery. I haven't heard the engine coming on once. It does concern my mechanical sensibilities that if I have floor it I'm asking for max power on a cold engine but I'm sure the manufacture has thought of this.
It's actually quite hard to tell when the engine starts as there is no rev counter on the default display and you can only hear the engine when it's revving quite high.
It's actually quite hard to tell when the engine starts as there is no rev counter on the default display and you can only hear the engine when it's revving quite high.
Its not 1972 any more chaps, its an interesting question but really not an issue, engines dont generally wear out these days and a hybrids engine has an electric motor to share the load with.
What tends to kill engines is design flaws and lack of servicing, and a lot of cars go to the scrapper for damage or an MOT that would cost more in terms of parts and labour than the car is worth.
What tends to kill engines is design flaws and lack of servicing, and a lot of cars go to the scrapper for damage or an MOT that would cost more in terms of parts and labour than the car is worth.
kambites said:
A few points:
Modern synthetic oils are vastly better at low temperatures than even older synthetics, let alone mineral oils.
PHEVs are designed to fire the engine up while there's still a fair bit of charge in the battery, meaning a large chunk of the total system torque after ICE start-up is still being provided by the electric motor. Hence the load on the ICE is initially very low.
The "constant running is better than constant stop-start" is a bit of an oversimplification. The real engine killer is too many cold starts, although obviously with a warm start on a conventional engine there will be a very brief period of low oil pressure. However, to counter the second point, many (maybe even all?) hybrids have electric oil pumps which fire up to get oil flowing before the engine itself is started.
Realistically for any given total mileage, the lower load on the ICE component of a hybrid will have more of a positive effect on its longevity than the negative effect of the extra stops and starts.
The oil might be better but liquid water (condensation) sitting on cylinder bores for long periods after a brief IC start may cause cylinder corrosion.Modern synthetic oils are vastly better at low temperatures than even older synthetics, let alone mineral oils.
PHEVs are designed to fire the engine up while there's still a fair bit of charge in the battery, meaning a large chunk of the total system torque after ICE start-up is still being provided by the electric motor. Hence the load on the ICE is initially very low.
The "constant running is better than constant stop-start" is a bit of an oversimplification. The real engine killer is too many cold starts, although obviously with a warm start on a conventional engine there will be a very brief period of low oil pressure. However, to counter the second point, many (maybe even all?) hybrids have electric oil pumps which fire up to get oil flowing before the engine itself is started.
Realistically for any given total mileage, the lower load on the ICE component of a hybrid will have more of a positive effect on its longevity than the negative effect of the extra stops and starts.
My wife ran a 2022 Yaris Hybrid as a company car for a couple of years, and it always struck me what an utterly s**t time the engine had on it.
One of the main scenarios for the engine cutting in would be hard acceleration where the engine would fire up (often from stone cold) and instantly start screaming its knackers off through the CVT for a few seconds, before switching off again.
Plenty of Priuses about on the same drivetrain with moon mileage though, so they seem to take it.
One of the main scenarios for the engine cutting in would be hard acceleration where the engine would fire up (often from stone cold) and instantly start screaming its knackers off through the CVT for a few seconds, before switching off again.
Plenty of Priuses about on the same drivetrain with moon mileage though, so they seem to take it.
CapScarlet said:
I was recently looking at a Mercedes GLC 300 de plug in hybrid which has a largish battery good for a 60-70 mile electric only range.
My question is this - I was always brought up on the assumption that to maximise longevity you should, firstly, warm up the engine and, secondly, constant running was better than continual stop / start.
I'm not an engineer but it seems that hybrids go against both these principles and, in particular the engine only fires up under heavy load.
Am I wrong?
My wife has just had a C class 300e delivered as her works car and i thought the same as you. When the electric runs out the engine fires up, you could be travelling at 70mph on the motorway. The engine is in and out as the battery charges again. Nice car though.My question is this - I was always brought up on the assumption that to maximise longevity you should, firstly, warm up the engine and, secondly, constant running was better than continual stop / start.
I'm not an engineer but it seems that hybrids go against both these principles and, in particular the engine only fires up under heavy load.
Am I wrong?
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