Fuel consumption concerns

[Hapsit12]

Hi there, 

I have recently purchased Lexus NX 300h F sport model, 2.5L Petrol Hybrid.

My concern is the fuel consumption. From what I looked online the average milage for F sport is 37.7mpg or 7.5l per 100km. 

I was driving on the German autoban at 180 to 200 km/h and my fuel consumption was shown at 22mpg or 13l/100km. Is this normal?

I then also did a very consistent cruise control drive at 95km/h for 1.5hours and average fuel consumption was shown at arround 7.4L/100km.

Just want to confirm if this is to be expected as this is my first larger car. I also have an audi a4 avant s line 2010 year 1.8 Turbo Petrol and it showed at 200km fuel consumtion of 8.9l/100km. 

The car did also have approx 17 liters of oil bottles in the back (Toyota gear box oil if ever needed, provided from previous owner) and 4x winter tires in the back.

Many thanks!

 

 

[Steve Oliver]

I would think that was highly likely at 111mph+ !!! I don't think anyone in the UK will be able to confirm the figures though as the speed limit here is 70mph... The NX is approx. 2 tons in weight without cargo, so takes a lot to lump it around - at very high speeds like that, there'll be barely any electric motor involvement. Very high speeds are not conducive to good mpg.

[Vince Donald]

Isn't the top speed on an NX 112mph?  Questioning the consumption at the top speed is erm questionable.

 

Vince

[Spacewagon52]

If you drive like a Formula One driver, you must expect Formula 1 consumption! 

There are threads on here that explain the driving technique for a hybrid. I did a short 5 mile journey on A roads the other day, with cruise set at 50 mph. At the end of the short journey the computer stated 44 mpg - but I do not get anywhere near that on my normal journeys.

Whenever you brake in a normal ICE car you are wasting fuel/energy. However, with a hybrid you are getting some of that wasted energy put back into the Battery. The Battery then supplements the ICE. With a very careful right foot in town you can run on electric only. My 400h is probably the least efficient hybrid Lexus have made but compared to the consumption of my RX 300 the hybrid gives far better mpg. The driving technique for good mpg in a hybrid is only slightly different from a normal ICE for good economy. The difference is that you tend to WANT to drive it economically. It suits the engine and the gearbox. Thrashing a hybrid makes the CVT gearbox whine loudly and that is probably why people complain about the CVT box. I think the CVT box is wonderfully smooth with no detectable gear changes.

Try your NX at 70 mph on cruise and then at 50 mph and you will see the obvious difference. If you are concerned about mpg then adjust your driving style to the hybrid method, it will not adjust itself to you!

Let us know how you get on. The engineering on these cars is amazing!

 

[Linas.P]

On 11/10/2020 at 1:22 PM, Hapsit12 said:

I was driving on the German autoban at 180 to 200 km/h and my fuel consumption was shown at 22mpg or 13l/100km. Is this normal?

I then also did a very consistent cruise control drive at 95km/h for 1.5hours and average fuel consumption was shown at arround 7.4L/100km.

The consumption at 180-200km/h is absolutely normal, if not somewhat low... I am assuming the speed is "indicated" rather than actual which will be ~8-10% lower. Meaning that you were doing ~ 175km/h (@110MPH) and at that speed 22MPG is about where I would expect car to be.

The consumption at 95km/h is somewhat above average - 7.4l ~32MPG, and I would expect NX to do ~38-44MPG at that speed. It would be normal perhaps on winder tyres... What are the tyres and tyre pressures?

11 minutes ago, Spacewagon52 said:

If you drive like a Formula One driver, you must expect Formula 1 consumption! 

180-200km/h is absolutely normal cruising speed. I would say ~160km/h is the baseline for cars on autobahn. 

Here is where I sadly have to give crown to diesels - in BMW 530d you can cruise all day long at 200km/h and have ~6-7l/100km. The reality is that hybrids are only good for cities and lower speeds (under 65MPH ~100km/h). Anything above that and they become just heavy petrol cars with a baggage of batteries in the back. Motorways even at retarded British speeds are not their strong point and will never be, high speed German autobahns are hybrid nightmare.

[Spacewagon52]

Quote:The reality is that hybrids are only good for cities and lower speeds (under 65MPH ~100km/h). Anything above that and they become just heavy petrol cars with a baggage of batteries in the back.

I am afraid I have to disagree with you sir! Provided you are not driving in excess over 70 mph, the consumption of my hybrid is a very reasonable 36 mpg. The faster you go over 65 mph then the fuel consumption will dip and probably significantly more in a hybrid for the reasons you gave. I do not consider a hybrid to be just a town car.

[rich1068]

17 minutes ago, Spacewagon52 said:

I am afraid I have to disagree with you sir! 

Now you've done it.

[Linas.P]

1 hour ago, Spacewagon52 said:

I am afraid I have to disagree with you sir! Provided you are not driving in excess over 70 mph, the consumption of my hybrid is a very reasonable 36 mpg. The faster you go over 65 mph then the fuel consumption will dip and probably significantly more in a hybrid for the reasons you gave. I do not consider a hybrid to be just a town car.

I don't see reason to argue whenever it is 70MPH or 65MPH... I general I think below around 60-70MPH hybrids are more fuel efficient than equivalent petrol car (especially in start/stop city traffic), 60-70MPH is where they become more or less equal and over around 60-70MPH is where petrol becomes more efficient - for the same reason I have mentioned and we both agreed about (diesel will drive circles around both thought). Under 70MPH my old IS250 non-hybrid could do 44-48MPG (although I assume you comparing it to RX400h?) and this is matched by new IS300h. However, around 90MPH IS250 still does 40MPG where on IS300h you only get 34MPG.

So... I am not sure what you are disagreeing with here, because what you have mentioned is exactly what I claimed, I have experienced the same myself and you just said you experienced it as well.. So you are saying that you disagree with me, but what you say is actually in agreement?! Are we just arguing about the language I use rather than the facts themselves? 

Instead of "hybrids are only good for cities and lower speeds" I probably should have said "hybrids only excel/are most beneficial at cities and lower speeds". Does that make it better?

[Spacewagon52]

Quote:Instead of "hybrids are only good for cities and lower speeds" I probably should have said "hybrids only excel/are most beneficial at cities and lower speeds". Does that make it better?

I am not sure that is the case, it is complicated and hard to generalize, but from, I admit, my limited hybrid experience, they are still more economical than a petrol at "reasonable" motorway speeds.

Sorry, have you owned a hybrid Linas? Are you speaking from experience or statistics?

[NemesisUK]

From my post in another tread..

"My 2019 RC300h averages 43 mpg in everyday driving around country roads and urban commutes.

When long distance high speed drives on motorways this average drops to mid to low 30's 

The RC300h hybrid system is definitely a glorified  Stop/Start and in that respect performs faultlessly in town/urban traffic. Let it loose on open roads and it is basically a traditional 2.5ltr petrol engined car, with an extra boost from the traction Battery when needed."

In contrast my 2005 2.7ltr CDI Mercedes would happily return 50+ mpg at the same sort of speeds but only achieve low 30's around town, in the summer. My 5.5ltr supercharged AMG would manage 27mpg on the motorway and creep into the higher teens around town.

The Lexus hybrid is really tuned to stop-start town driving but with the new generation UX and ES breaking that mould with significantly better high speed economies 

[Hatat]

On 11/10/2020 at 1:22 PM, Hapsit12 said:

Hi there, 

I have recently purchased Lexus NX 300h F sport model, 2.5L Petrol Hybrid.

My concern is the fuel consumption. From what I looked online the average milage for F sport is 37.7mpg or 7.5l per 100km. 

I was driving on the German autoban at 180 to 200 km/h and my fuel consumption was shown at 22mpg or 13l/100km. Is this normal?

I then also did a very consistent cruise control drive at 95km/h for 1.5hours and average fuel consumption was shown at arround 7.4L/100km.

Just want to confirm if this is to be expected as this is my first larger car. I also have an audi a4 avant s line 2010 year 1.8 Turbo Petrol and it showed at 200km fuel consumtion of 8.9l/100km. 

The car did also have approx 17 liters of oil bottles in the back (Toyota gear box oil if ever needed, provided from previous owner) and 4x winter tires in the back.

Many thanks!

 

 

I had the same car model year 2017 though for a year and just recently switched to an RCF.

I noticed it while driving long motorway sessions that mpg dropped dramatically so I asked my local dealer I was told in long motorway driving only petrol engine is involved unless you drive lower speed to involve electric engine mpg should drop having 2.5 engine, to sum up fuel efficiency can be only good if you drive a little of motorway and City Drive a combo maintain good economy.

I tested in city only and I had 22mpg too so I had to drove a few miles of motorway to charge the Battery which I think is ridiculous.

[Spacewagon52]

The "BEST" mpg I have had on a long motorway run in my RX 300 was 28 mpg

In the 400h I achieved 36 mpg. With lockdown my experience with the hybrid is limited but I found it more economical on a long run than a straight 3.0 litre RX.

What does surprise me is that NX 300h owners do not seem to get much better mpg than RX 450h owners - 2.5 litre vs 3.5 litre?.

[royoftherovers]

48 minutes ago, Spacewagon52 said:

The "BEST" mpg I have had on a long motorway run in my RX 300 was 28 mpg

In the 400h I achieved 36 mpg. With lockdown my experience with the hybrid is limited but I found it more economical on a long run than a straight 3.0 litre RX.

What does surprise me is that NX 300h owners do not seem to get much better mpg than RX 450h owners - 2.5 litre vs 3.5 litre?.

So many owners quote On Board Computer (OBC)  figures Davey which is wholly misleading.

I was once in my GS450h going downhill with the wind behind me and the OBC showed 100 mpg......wow!

Typically OBC readings until approx 2010 year of manufacture showed over-readings of 8%.

[Spacewagon52]

Those two reading were done tank to tank John but your warning about over optimistic computers is duly noted!

[Linas.P]

19 hours ago, Spacewagon52 said:

I am not sure that is the case, it is complicated and hard to generalize, but from, I admit, my limited hybrid experience, they are still more economical than a petrol at "reasonable" motorway speeds.

Sorry, have you owned a hybrid Linas? Are you speaking from experience or statistics?

What is "reasonable" motorway speed? According to statistics average speed on UK motorways was 82MPH in 2019. Is that reasonable? On top of that UK has one of the lowest national speeds in Europe, other nations having 80-90MPH and what is relevant for this topic - Germany having no limits on part of the network (from my experience that translates into actual 100-120MPH cruising speeds). Is that not reasonable?

That said at exactly 70MPH (actual, which would indicate like ~76MPH) the IS250 will have same fuel economy as IS300h, at 80MPH (87 indicated) IS250 will have better economy than IS300h, but IS300h will have significantly better fuel economy in start/stop town driving. How much better? well it depends at how busy it is, how often you stop, what is the speed, what time you drive, what route you take etc. but generally hybrid will mostly be more fuel efficient than equivalent petrol. Is there any difference between what we saying or agreeing on here?

I feel that all that said it is fair to summarise then, that hybrids are most beneficial in cities? Is it not? 

If my assumption is correct, then your comparison of RX300 (assume this is mk2 model with 1MZ-FE engine) and RX400h (mk3 with 2GR-FXE engine) is fundamentally flawed. Let me explain why... you comparing two engines which are technologically quite different. RX300 is an old 3L V6 (1MZ-FE) without direct injection (significantly less fuel efficient) and RX400h is significantly newer 3.5L V6 with direct injection and Atkinson cycle (2GR-FXE). Not to mention that I would consider 1MZ-FE under-powered and over-stressed for the large and heavy car like RX, which will always translate in poor fuel efficiency. And 2GR-FXE will have more modern gearbox and overall drive-train increasing fuel efficiency. So in terms of fuel efficiency RX400h will beat RX300 in any circumstances with or without hybrid e.g. simple non-hybrid RX350 (2GR-FSE) would beat RX300 as well.

In terms of my experience, I have not owned hybrid myself, but to be fair I did more miles in various Lexus 300h's than I did in my own RC200t (3000 mile+). 

[Hatat]

26 minutes ago, Linas.P said:

What is "reasonable" motorway speed? According to statistics average speed on UK motorways was 82MPH in 2019. Is that reasonable? On top of that UK has one of the lowest national speeds in Europe, other nations having 80-90MPH and what is relevant for this topic - Germany having no limits on part of the network (from my experience that translates into actual 100-120MPH cruising speeds). Is that not reasonable?

That said at exactly 70MPH (actual, which would indicate like ~76MPH) the IS250 will have same fuel economy as IS300h, at 80MPH (87 indicated) IS250 will have better economy than IS300h, but IS300h will have significantly better fuel economy in start/stop town driving. How much better? well it depends at how busy it is, how often you stop, what is the speed, what time you drive, what route you take etc. but generally hybrid will mostly be more fuel efficient than equivalent petrol. Is there any difference between what we saying or agreeing on here?

I feel that all that said it is fair to summarise then, that hybrids are most beneficial in cities? Is it not? 

If my assumption is correct, then your comparison of RX300 (assume this is mk2 model with 1MZ-FE engine) and RX400h (mk3 with 2GR-FXE engine) is fundamentally flawed. Let me explain why... you comparing two engines which are technologically quite different. RX300 is an old 3L V6 (1MZ-FE) without direct injection (significantly less fuel efficient) and RX400h is significantly newer 3.5L V6 with direct injection and Atkinson cycle (2GR-FXE). Not to mention that I would consider 1MZ-FE under-powered and over-stressed for the large and heavy car like RX, which will always translate in poor fuel efficiency. And 2GR-FXE will have more modern gearbox and overall drive-train increasing fuel efficiency. So in terms of fuel efficiency RX400h will beat RX300 in any circumstances with or without hybrid e.g. simple non-hybrid RX350 (2GR-FSE) would beat RX300 as well.

In terms of my experience, I have not owned hybrid myself, but to be fair I did more miles in various Lexus 300h's than I did in my own RC200t (3000 mile+). 

 

[Spacewagon52]

2 hours ago, Linas.P said:

What is "reasonable" motorway speed? According to statistics average speed on UK motorways was 82MPH in 2019. Is that reasonable? On top of that UK has one of the lowest national speeds in Europe, other nations having 80-90MPH and what is relevant for this topic - Germany having no limits on part of the network (from my experience that translates into actual 100-120MPH cruising speeds). Is that not reasonable?

That said at exactly 70MPH (actual, which would indicate like ~76MPH) the IS250 will have same fuel economy as IS300h, at 80MPH (87 indicated) IS250 will have better economy than IS300h, but IS300h will have significantly better fuel economy in start/stop town driving. How much better? well it depends at how busy it is, how often you stop, what is the speed, what time you drive, what route you take etc. but generally hybrid will mostly be more fuel efficient than equivalent petrol. Is there any difference between what we saying or agreeing on here?

I feel that all that said it is fair to summarise then, that hybrids are most beneficial in cities? Is it not? 

If my assumption is correct, then your comparison of RX300 (assume this is mk2 model with 1MZ-FE engine) and RX400h (mk3 with 2GR-FXE engine) is fundamentally flawed. Let me explain why... you comparing two engines which are technologically quite different. RX300 is an old 3L V6 (1MZ-FE) without direct injection (significantly less fuel efficient) and RX400h is significantly newer 3.5L V6 with direct injection and Atkinson cycle (2GR-FXE). Not to mention that I would consider 1MZ-FE under-powered and over-stressed for the large and heavy car like RX, which will always translate in poor fuel efficiency. And 2GR-FXE will have more modern gearbox and overall drive-train increasing fuel efficiency. So in terms of fuel efficiency RX400h will beat RX300 in any circumstances with or without hybrid e.g. simple non-hybrid RX350 (2GR-FSE) would beat RX300 as well.

In terms of my experience, I have not owned hybrid myself, but to be fair I did more miles in various Lexus 300h's than I did in my own RC200t (3000 mile+). 

You have made some very valid points regarding the difference in engine efficiency, which I must be honest I had not taken into consideration. I presume you mean that the CVT gearbox is far more efficient than the 5 speed one on my RX 300. It has been stated on here that the 2.5 litre engine, used in the 300h, is an older design and hence why the more modern 3.5 litre hybrid can come close to its mpg as a hybrid. I concur with you Linas that hybrids are far more efficient in town driving compared with ICE cars. However, I am reluctant to concede that they are totally inefficient at Britain's motorway legal limit. I challenge your statistic that the AVERAGE speed on a motorway is 82 mph! Sorry Linas but you are not getting away with that one! 

Our differences on this subject are small but I can't let you get away scot-free with dubious and inaccurate statistics!

I rest my case M'Lud!

[Linas.P]

22 hours ago, Spacewagon52 said:

I challenge your statistic that the AVERAGE speed on a motorway is 82 mph!

I will have to concede on this one (for now), I just could not find my source... it is possible that I took the figure out of context or it was for specific motorway. However, I definitely have not invented it myself - it was statement along the lines of "average free-flowing traffic speed on motorway is now 82MPH" taken from some respectable newspaper (like The Guardian). I will report back once I find it. 

22 hours ago, Spacewagon52 said:

I presume you mean that the CVT gearbox is far more efficient than the 5 speed one on my RX 300.

It has been stated on here that the 2.5 litre engine, used in the 300h, is an older design and hence why the more modern 3.5 litre hybrid can come close to its mpg as a hybrid.

I concur with you Linas that hybrids are far more efficient in town driving compared with ICE cars. However, I am reluctant to concede that they are totally inefficient at Britain's motorway legal limit.

Not necessary, even newer automatic 6/8 speed transmission is still more efficient due to things like torque converter lock-out which was not present in old 5-speed.

2GR-FXE (400/450h) is actually older than 2AR-FSE (like IS300h) and is based on 350 (2GR-FSE) which is rather old design. There is new 300h A25A-FXS which is improved version of 2AR-FSE as well (like ES300h). The only "newer" 3.5L hybrid is the system branded as 500h and engine code 8GR-FXS (LC/LS) and it is different design and not based on old 2AR-FSE.

To clarify what I was comparing in order of efficiency from most to least are - 450/400h 2GR-FXE vs. 350 2GR-FSE vs. 300 1MZ-FE

I never said hybrids are totally inefficient on motorway - I just said that simple and comparable petrol engine will be just as much if not more efficient due to hybrid basically becoming a heavier version of the same petrol engine when at speeds above 60-70MPH. This could be further extended to any road with very low traffic where one can drive at very consistent speed without braking, as the whole benefit of hybrid system is to reduce fuel wasted when braking and accelerating. Not so much beneficial when cruising at constant speed and actually could be detrimental if batteries are regenerating.

[Spacewagon52]

I think we now agree Linus! Though you have not redacted your dubious statistic of average motorway speed!

However, I think we are closer to a concurrence! 

[Linas.P]

7 minutes ago, Spacewagon52 said:

I think we now agree Linus! Though you have not redacted your dubious statistic of average motorway speed!

However, I think we are closer to a concurrence! 

well... to begin with I can't because one can only edit the post for short time! - so let's just say I was not able to prove it yet.

[NemesisUK]

This is an interesting little document

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/812500/vehicle-speed-compliance-statistics-2018.pdf

 

[Spacewagon52]

37 minutes ago, Linas.P said:

well... to begin with I can't because one can only edit the post for short time! - so let's just say I was not able to prove it yet.

Wow! Thank you Peter!

A response from you Linas?

Can I help? "Sorry I was mistaken, I did not understand what average means."

[Linas.P]

@Hapsit12 - sorry for taking over your thread (that is sadly reality of public discussion - more off topic tan on it)... 

Does the answer satisfies you? That is - your fuel consumption seems normal for ~175kph, but on the high side for 95kph which could be due to tyres or other factors? or you still have concerns with fuel consumption?

@Spacewagon52 - no worries, I am still researching... 

[Zotto]

It sounds strange to me that nobody has considered in answers the great difference in air resistance from driving a large front area SUV compared to a minor and more aerodynamic shape of a saloon or a coupe, this is the main reason because at high speed fuel consumption rise so much  in SUVs of all kinds and not specifically hybrid ones. The solution? Do not exceed 70-75 mph or don't care about sparing fuel. Besides, I noticed that NX300h compared to RX450h at speed over 80 mph has a worse fuel consumption, probably because higher rpm; same reason because usually diesel cars have a good consumption in high speed cruising, provided that they have a advantage more, the specific energy in diesel fuel is higher than in gasoline. The big advantage for hybrids, energy recovery during braking is quite noticeable in city driving and wherever there are many variations in speed, and of course is less noticeable in motorways.

[Linas.P]

I would not say... "not considered"... I have consider it, but thought this was quite obvious. That is why I said fuel consumption normal for ~175kph, what I think is high is the consumption ~95kph.

As well re: 300h vs. 450h - it is not only RPM, there are points where larger and more powerful engine is more fuel efficient, because there are certain speeds and loads where engines are very efficient and very inefficient. For example maybe over 80MPH 450h just get's to it's "efficient power range", where 300h is already under-powered and thus have to do a lot of extra work and is inefficient. At the same time @55MPH 300h is more efficient because that is where it's most efficient range is.

Looking at simple petrol/diesel examples that is still true e.g. 2.0l diesel/petrol engines will generally be more efficient around town and at lower speeds, but once you cruising at 120MPH the 3l petrol/diesel will be more efficient as they don't need to work as hard at those higher speeds.

But in general I do agree - for 120MPH/200KPH autobahn driving SUVs or Hybrids are not the best choice, especially if good fuel consumption is the goal.