Discussion
MrGTI6 said:
MPG figures for all plug-in hybrids are totally pointless. It's almost infinite depending on how regularly the car is charged.
Yep, this. At least WLTP tests now measure both from full battery and empty and apply a “utility factor” based on the electric range to attempt to show how it might perform in an average driver’s usage. We had a Golf GTE. If I did several hundred motorwa miles in one go I’d get about 45mpg overall. But in our normal everyday use I’d go months (and 2000+ miles) between putting petrol in the tiny tank. What’s a correct or realistic mpg figure to assign it?
MrGTI6 said:
MPG figures for all plug-in hybrids are totally pointless. It's almost infinite depending on how regularly the car is charged.
This!!In time, a layman translatable economy unit must be agreed, which gives the user an indication of the energy (and therefore the cost) that each mile will cost when using their electric vehicle. At the moment, the cost is that low compared to the cost of filling with fuel, that the reporting effectively ignores the cost of charging entirely .... similarly, it ignores the CO2 required to get the energy to the battery in the first place, albeit in exactly the same deficient way that the CO2 for internal combustion is only reported at the exhaust tailpipe, and does not allow for extraction, transport and refinement.
The quoted mpg is for the official test cycle. The car will be able to do almost all that test on battery and so only use a small amount of fuel, hence the mpg figure. If the test had been a bit longer then the mpg would drop.
I used to have a mitsubishi PHEV which quoted mpg of something like 135mpg. Battery range was about 25miles. If I used it for journeys less than this distance (my daily commute) then I could go all week and use no fuel so infinite mpg. If I went on a journey over 25 miles then the mpg dropped. On a long motorway journey it could drop to 35mpg.
MPG is journey distance dependant with this type of power train.
The official test at that time was derived before the era of hybrids and electric cars so didn't deal with them very well. It was also law that manufacturers had to quote the official test mpg (to prevent exaggerated mpg claims
)
I used to have a mitsubishi PHEV which quoted mpg of something like 135mpg. Battery range was about 25miles. If I used it for journeys less than this distance (my daily commute) then I could go all week and use no fuel so infinite mpg. If I went on a journey over 25 miles then the mpg dropped. On a long motorway journey it could drop to 35mpg.
MPG is journey distance dependant with this type of power train.
The official test at that time was derived before the era of hybrids and electric cars so didn't deal with them very well. It was also law that manufacturers had to quote the official test mpg (to prevent exaggerated mpg claims
)Moving a car about takes energy.
The faster you do that, the more energy it takes.
For any efficiency level, the faster you move about, the more energy you use.
That's the difference between "efficiency" and "consumption".
The manditory legaslative test cycles try to be an average kind of driving cycle, Not too fast, not too slow. but they certainly don't represent the worst case.
For example, at a constant 50 mph, a typical passenger car requires about 20 bhp to push it along. And yet we drive cars that have hundreds of bhp. Clearly the difference between the minimum possible consumption and the maximum possible consumption is large.
For a battery electric hybrid, the picture is confused because when it runs on electricity, it doesn't use any fuel. So if you drive short journeys at low speeds, entirely on electricity, then your "mpg" is very high. But drive hard, use the engine and all it's power, and the result is a a poor mpg.
The faster you do that, the more energy it takes.
For any efficiency level, the faster you move about, the more energy you use.
That's the difference between "efficiency" and "consumption".
The manditory legaslative test cycles try to be an average kind of driving cycle, Not too fast, not too slow. but they certainly don't represent the worst case.
For example, at a constant 50 mph, a typical passenger car requires about 20 bhp to push it along. And yet we drive cars that have hundreds of bhp. Clearly the difference between the minimum possible consumption and the maximum possible consumption is large.
For a battery electric hybrid, the picture is confused because when it runs on electricity, it doesn't use any fuel. So if you drive short journeys at low speeds, entirely on electricity, then your "mpg" is very high. But drive hard, use the engine and all it's power, and the result is a a poor mpg.
Usual PHEV nonsense. In mine, on the rare occasions I drive to work, I can get there and back on battery alone. So either infinite MPG, or your choice of carbon-equivalent numbers. On the other hand, driving (spiritedly, I admit) the 300 miles or so to our place in France, back when that was a thing, I got about 28mpg. Which is pretty well the same as our XC90 PHEV, and worse than any of my Porsches, none of which is less than 28 years old. Not necessarily progress, therefore, but the Porsches do rather worse around town, so it rather depends on your usage pattern.
I drive an i8 daily.
It's an simple as, it depends on the journey distance and speed.
In the 'sweet spot' i often see 350+ mpg. I.e. a journey of around 15- 20 miles, no heavy foot, speeds upto 60 odd mph.
The standard cycle for the benchmark test is closer to the above cycle than the average of typical real world driving.
Equally, drive loads of journeys including loads of fast motorway, heavy foot, short local journeys etc etc, the average drops to 45 mpg.
Still much better than similar performance car, which would give 18-25mpg in reality.
Compare same driver (me), over a year of same type of trips: average mpg:
My 340 bmw: 30 mpg. My i8 :46 mpg.
Ok?
It's an simple as, it depends on the journey distance and speed.
In the 'sweet spot' i often see 350+ mpg. I.e. a journey of around 15- 20 miles, no heavy foot, speeds upto 60 odd mph.
The standard cycle for the benchmark test is closer to the above cycle than the average of typical real world driving.
Equally, drive loads of journeys including loads of fast motorway, heavy foot, short local journeys etc etc, the average drops to 45 mpg.
Still much better than similar performance car, which would give 18-25mpg in reality.
Compare same driver (me), over a year of same type of trips: average mpg:
My 340 bmw: 30 mpg. My i8 :46 mpg.
Ok?
I've never under stood the i8. I know it has its proponents. It's got super car looks but an also ran EV power train with a small 7kWh battery (Wikipedia) and 1.5 3 pot turbo ICE.
It is capable of very good mpg but only over small distances driven gently??
It is expensive, looks to be a night mare to support and you don't get the aural excitement and fun of extracting the best out of a V10 or V12 engine.
It is capable of very good mpg but only over small distances driven gently??
It is expensive, looks to be a night mare to support and you don't get the aural excitement and fun of extracting the best out of a V10 or V12 engine.
granada203028 said:
I've never under stood the i8. I know it has its proponents. It's got super car looks but an also ran EV power train with a small 7kWh battery (Wikipedia) and 1.5 3 pot turbo ICE.
It is capable of very good mpg but only over small distances driven gently??
It is expensive, looks to be a night mare to support and you don't get the aural excitement and fun of extracting the best out of a V10 or V12 engine.
Expensive? I see them in the classifieds from £35k which doesn't seem a lot for me personally given how good they look and how useable they are (even as a daily). This would be my choice of a DD all day long. It is capable of very good mpg but only over small distances driven gently??
It is expensive, looks to be a night mare to support and you don't get the aural excitement and fun of extracting the best out of a V10 or V12 engine.
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