NX WLTP data

Martin J · April 29, 2019

I've seen a couple of references elsewhere on the forums to the WLTP fuel economy and emissions regime. But I've only just noticed the figures for the NX. Two things strike me: (i) the figures are much worse than the old NEDC figures; and (ii) the RX now performs as well as the NX, having suffered less from the transition, with, counterintuitively, a lower CO2 emissions figure (134g/km vs 135 for the NX).

On (i) the NX WLTP fuel consumption range (35.7 to 37.7 mpg) is now actually worse than many owners will be achieving in mixed driving, and well below the 38 - 46 range between fills I've seen. On (ii), the data suggest that we could have had an NX450h with little if any increase in consumption and emissions, with much better performance and refinement...

LordByronUK · April 30, 2019

That's because the NX300h is hands down an under-powered vehicle, and the engine (although very similar to the IS300h) has to work harder at any given speed/acceleration due to increased vehicle weight and higher drag coefficient. The RX has a much better power/weight ratio, which is why it can get around the same fuel economy, and be much faster at the same time. IMO it was a big mistake releasing the NX hybrid with an older/weaker IS power train!

The hybrid NX is crying out for a small V6 hybrid, or a plug-in 4-cylinder variant with a more powerful electric motor, that would be perfect (around ~250HP with more torque). If I could go back in time I'd probably go for the 2.0litre turbo variant, much more fun and fuel economy not much worse on the motorway I hear. I mean what were the engineers thinking putting a weaker engine in than the IS, when the NX is much heavier and has worse drag, completely stupid decision and made just for financial reasons I'm sure. I wish more people would speak up about this and put pressure on Lexus to improve upon this terrible decision with the next big refresh.

People can disagree with me, but I have an IS, partner an NX and I'm telling you honestly it's an under-powered vehicle. Even at the dealership they say it's under-powered, and that's the main reason for the poor fuel economy. If you drive the NX like a regular vehicle, you'll get about the same fuel economy as a CX5 or Tiguan, so basically the hybrid system in the NX just doesn't work that well I'm afraid, very disappointed with the vehicle overall, and many share this view. The NX sells well because it looks great, let's be honest about it, and it does look great!

I'm going to put good money on NX sales in the UK dropping off a cliff this year now that the new RAV4 has been released, which is not only faster, but has better fuel economy!!! Again, it all comes down to the physics, the RAV4 (although a similar engine) has a better power to weight ratio than the NX. This fact, combined with the embarrassing WLTP numbers that have now come out for the NX are the reasons why I predict NX sales will tank this year.

Time for a big refresh Lexus...

First_Lexus · May 2, 2019

The question of whether a vehicle is 'underpowered' depends very much on driving style, previous experience and expectations. I drive in a relaxed manner and find the available power in the NX absolutely fine, and it certainly has far more 'power' than my previous Honda CR-V 2.0 litre petrol auto. Based on my experience, my opinion isn't that it is 'underpowered.' I didn't buy it for power, I have another car for that.

Where economy is concerned, I get 40-42mpg as an average in mixed (but virtually no motorway) driving but can achieve 45-47 on my 15 mile commute if I really try. In 2k miles in a new RX - with the same driving style on the same roads - I got 30-32mpg. My old VW Tiguan diesel, albeit with more motorway driving, achieved 35-40mpg. Others may achieve different results - I can only relate my own experience.

@LordByronUKYour opinion based on having an IS and an NX doesn't surprise me. The same engine in a bigger car - and with AWD capability - is almost bound to be 'slower.' Forums are interesting and can be useful. Opinions are fascinating. It's only when opinions are presented as facts that they start to lose credibility. The NX was my choice over similar Volvo, Skoda and Subaru models (amongst others) because of the interior quality, comfort and general quietness. I'm happy with all of those things having owned it for some time, but will look at the RAV when the time comes. Those on here that have driven it and shared their views say it is a disappointment - especially on general refinement. I'll make my own mind up at some point.

ColinBarber · May 2, 2019

On 4/30/2019 at 1:23 PM, LordByronUK said:

the RAV4 (although a similar engine) has a better power to weight ratio than the NX

The engine is very different - two generations ahead of the NX.

The NX engine is actually a generation behind the IS engine, that is why it is down 25 bhp and 11 Nm and that combined with the extra weight and worse aerodynamics makes a noticeable difference.

ColinBarber · May 2, 2019

2 hours ago, First_Lexus said:

Those on here that have driven it and shared their views say it is a disappointment - especially on general refinement. I'll make my own mind up at some point.

The old or new one? The new ones have only just come into showrooms. If it is like the current Prius then the refinement will be better than the NX.

First_Lexus · May 3, 2019

8 hours ago, ColinBarber said:

The old or new one? The new ones have only just come into showrooms. If it is like the current Prius then the refinement will be better than the NX.

^^ The new one. Comments are on the thread 'CarWow Review' on the NX forum from @sandj

LordByronUK · May 3, 2019

13 hours ago, ColinBarber said:

The engine is very different - two generations ahead of the NX.

The NX engine is actually a generation behind the IS engine, that is why it is down 25 bhp and 11 Nm and that combined with the extra weight and worse aerodynamics makes a noticeable difference.

Indeed, I was told the same by the dealership that the version of the NX300h engine is an older version of the 2AR-FXE engine, 2 generations behind latest RAV4. It is a strange decision that they decided to put such an old version into the NX300h, even the IS300h has a more modern variant. Maybe they did it as a cost cutting measure, and this is where my issues lie. It is quite an expensive luxury vehicle, and luxury vehicles of this price range should guarantee a luxury drive, meaning adequate power at most road speeds. With the current NX engine, for me personally it doesn't feel like a luxury drive above 40mph, it feels like the car struggles quite a lot and the engine note is quite unpleasant, and this is not what one would expect from a ~36-45k car. To call a car luxury at this price point, it should at least be able to gracefully waft to top motorway speeds, something the IS/ES300h achieve quite well, the NX300h does not!

The debate around whether a car or not is under-powered is somewhat subjective I admit, but the general consensus from journalists, some owners and dealerships I've spoken with are that the NX300h is under-powered for the type of vehicle it is, especially at its price point. You could put a better engine in it and get just as good, if not better fuel economy, and a better drive. I just hope that Lexus hurry up with either putting in the new RAV4 engine, or come out with a plug-in variant with a more powerful electric motor. Seems like the former though is more likely in the short term.

I believe the NX does have massive potential, and overall I do like it, fantastic looking car, great handling and very comfortable, but the engine and economy are pain points that stop the vehicle from achieving its true potential.

ColinBarber · May 3, 2019

8 hours ago, LordByronUK said:

Indeed, I was told the same by the dealership that the version of the NX300h engine is an older version of the 2AR-FXE engine, 2 generations behind latest RAV4. It is a strange decision that they decided to put such an old version into the NX300h, even the IS300h has a more modern variant.

The NX engine came from the front wheel drive Camry and is indeed the 2AR-FXE. Toyota don't have the IS300h engine/transmission in front wheel drive configuration - that engine is the 2AR-FSE. They are from the same 2AR family but main differecet is lack of direct injection and lower compression ratio on the NX engine - something that should be simply enough to resolve but I guess that was a financial and time to market decision.

The new RAV4 engine (A25A-FXS) is different in design to the older 2AR - different block design and heavily reworked components with more electronic controls - e.g. electric water pump and thermostat. It is much more efficient than both the NX and IS engine.