Lexus Nx True Mpg

ColinBarber · July 22, 2015

What is the point of quoting % ,when everyone knows it's crap going uphill?

To answer the person's question and to explain that it is different to an IS300h.

You have made your position clear in this thread, I suggest you move on.

sc489 · July 22, 2015

Is it really a lack of power? I have an IS300h, which I appreciate is different and weighs less, but power is not an issue, are you referring to the CVT gearbox screaming when any power is needed, giving the illusion? I find the IS surprisingly swift, particularly if driven around the gearbox to keep revs down, it is so refined it feels a lot slower than it is.

The NX has a 20% lower power to weight ratio compared to the IS300h due to the extra weight and giving up 28 bhp. All of that power loss is from the petrol engine which then has to work harder to get up hills.

Isn't the torque / weight ratio more important than the power / weight ratio?

I decided not to buy the NX a while ago following a test drive which gave very poor mpg on the test route. If you are looking to buy a refined SUV style car, I was impressed by the new Subaru Outback petrol auto version. It was as refined as the NX, more economical, cheaper, fully 4WD and has much greater luggage space.

ColinBarber · July 22, 2015

Fair point. It is a similar situation there too, although not quite so high. The engine's peak torque is available at quite a high rpm, combined with the CVT means the engine will rev quite high when put under load.

rayaans · July 22, 2015

Hmm come to think of it, my 2004 RX300 had no trouble getting up hills and it only had 201 hp. However, it did go to a lower gear on hills to help pull the car up.

With CVTs there's no gradient sensor so you have to modulate using the accelerator pedal whereas in my RX300 it'd automatically go to a lower gear if it thought the car wasn't going to get up

Goggy · July 22, 2015

I've watched lot's of reviews on You Tube, but so far none have come up with the problem of driving up hills, even the USA and Canada reviews. I would have thought that if it was that bad it would have showed up somewhere by now. I have watched about two dozen.

ColinBarber · July 22, 2015

It doesn't have a problem driving up a hill. It's the same as the CT, there is certainly enough power for the size and weight of the vehicle to get up any inclined road in this country. The issue is that the engine revs up quite high when under moderate load, for example when going up a hill.

Goggy · July 23, 2015

Ahhh I see. Yes, my CT does that, although being hard of hearing I don't hear it much, if at all. :) Yes, it does go up hills fine.

Martin J · July 23, 2015

This discussion reminds me of how someone in Sheffield, after a brief drive in a Prius, declined to purchase one because, as they put it, “it struggles on hills”, of which Sheffield has plenty.

I found this amusing, having crossed both Sheffield and the Alps a number of times in a fully-laden Prius. Obviously the hybrid system dispenses with the linear relationship between combustion engine revs and road speed which conventional drivetrains deliver (and which motoring journalists seem to be unable to manage without). And the Prius is certainly loud, not to say raucous, under load uphill, as the hybrid system directs engine revs to rise quickly into the peak power and torque ranges. Sometimes under these circumstances the engine’s generating excess power and charging the traction Battery simultaneously. But there really is ample power for hill climbing, and the loud noise is not to be confused with that made by a 1-litre supermini being caned in first gear, for example. Struggling it isn’t.

The NX drivetrain so far feels eerily similar, except that it’s of course much quieter right across the operating range. In my limited experience the hybrid system doesn’t send the revs high nearly as often as it does in the Prius, presumably reflecting the NX’s better power-to weight ratio and some software development. On the rare occasions it does, it’s still fairly loud by luxury vehicle standards. But while the NX300h is no rocketship, I can’t believe that with between 76 and 84KW/tonne it’s underpowered. The petrol engine may be a little intrusive on those occasions when it’s operating at high revs, but I’m more than willing to accept those occasions as a trade-off for the 95% of the time that the NX is so much quieter and more refined than its competitors, especially the diesel ones. Others may not be, of course.

Realise this is the mpg thread, so I’ll just say that I’m still on 46 mpg, but haven’t yet finished the first tankful!

DJP · July 23, 2015

^^

Nail on head

Sent from my iPad using Lexus OC

rayaans · July 23, 2015

^^

Nail on head

Sent from my iPad using Lexus OC

I don't know. I've driven the NX300H and a lot of other cars including the CT. I had no issues with the CT going up the hill, or my previous RX300 or even my RX450H. The IS300H is fine too. The NX300h is an odd one, it has to rev alot to get up a hill. I was literally flooring it and it just gets tiring. Reminds me of my son's friends Fiat 500 which has trouble getting up a hill. Recently been sorted with software change.

DJP · July 24, 2015

I guess this gives me another reason to go and book a test drive I'll pay particular attention to some local hills and compare to my IS.

July 24, 2015

Yes i agree it is a strange one we also had a RX 300 in the past which was a very refined car,only problem was the swerving every time you passed a filling station.As i have said before the Nx is a really nice well put together car as you would expect from Lexus but we are not imagining this hill problem it is there and after nine months of ownership we would know.

Simple answer is that issue apart the Nx is great, so its weather you can live with it?

rayaans · July 24, 2015

Yes i agree it is a strange one we also had a RX 300 in the past which was a very refined car,only problem was the swerving every time you passed a filling station.As i have said before the Nx is a really nice well put together car as you would expect from Lexus but we are not imagining this hill problem it is there and after nine months of ownership we would know.

Simple answer is that issue apart the Nx is great, so its weather you can live with it?

I guess it depends where you live. London or Manchester might not be a bad place for the NX300h as hills are few and far between. Yorkshire on the other hand is a different story!

I guess many people only find out when they have bought the car already as most dont tend to go on hills on test drives.

Valkirk · July 26, 2015

Hybrid MPG is affected more by the driver than the car - make sure you have the car in Eco mode, check tyre pressures and pay attention to the display showing where power is coming from - when at a 30-40 mph steady cruise you sometimes need to ease of the accelerator and then gently press back to make sure only running on Battery. If in a traffic light jam switch into electric mode so engine doesn't cut on every time you move forwards.

Route planning and time is everything, slow but constant moving traffic is the best economy, the same run getting caught by traffic lights, pedestrian crossing etc. can have a significant impact - a 9am run from Croydon to Sidcup in the RX (with a warmed up engine) got 52.8mpg, after 25 miles on the motorway (65-70mph) after that it was still 43.7mpg

Braking and accelerating are the things that ruin economy, try to read road ahead and minimise both.

If you want an easy win and the weather isn't hot just turn the AC off.

Hybrid systems help in stop start, low speed steady traffic - they excel in towns. Motorways are their biggest weakness, the hybrid system does nothing to help and just results in extra weight.

Could easily get 30mpg on motorway in my ISF but my short town work journey would be about 18mpg compared to 30mpg in the RX, in between those cars I had a 1.8 turbo Merc C Class (C250) rated at 45 urban, 60mpg extra - struggled to get 40mpg with AC off on the motorway and that short town work journey was 16-20mpg!

TLDR - Hybrid for town, short, low speed. Diesel for motorway, killing people with NOx....

rayaans · July 26, 2015

The only difference between the NX300H and the cars you mention is that the other cars have ALOT more power. A 2.5l 4 pot is never going to be as good at hauling a 1.8 tonne vehicle as a 3.5l V6 is and has to work much harder resulting in lower MPG

hunslet · July 26, 2015

I have to disagree with something that Valkirk says regarding Eco mode. My understanding is that even the dealers are telling Lexus owners not to rely on Eco mode as a lot of the time you are having to push the engine. In many situations you are better off using sport mode. I have just been to the Lake District and found the hills there to be quite pleasant in Sport mode but a pain in Normal.

I am back home in sunny staffordshire now and since my last visit to the petrol station i have been getting 45 mpg

RcF · August 1, 2015

35.1 mpg. going for service next week with 11,000 miles

will change it for a isf soon.

rayaans · August 2, 2015

Just thought I'd add my RX450H for reference.

218 mile trip to Birmingham and back.

Whole trip was in Sport mode with 3 adults, one very big "child" of 16 years and a 5 year old + my wife's extra baggage about 20kg worth. Also full tank of fuel.

Speed was about 70-80mph but was naughty and hit 100mph after becoming annoyed by the 50mph roadworks.

34mpg!! Didn't even try lol

Considering some of you get that in the NX I'm quite chuffed with myself

Goggy · August 2, 2015

Oddly, in the USA the official Lexus MPG is 32MPG for the NX300h and 24MPG for the NX300t. So in that country Lexus have to tell the truth, I think by law they have to be accurate, not like here where Lexus and other manufacturers test cars under perfect conditions with no air con etc on which is nonsense.. Not sure why the UK government still do no not do something about it, as it is clear that the true MPG is nowhere near what they claim the cars will do. Why not just come clean and tell the truth?

So in the USA most buyers are very happy that when they buy a NX300h and find they are getting 35-40MPG, which has turned into a very positive selling point for the car, unlike here where buyers, not realising the claimed figures are well off true MPG, get a bit cheesed off.

Come on Lexus, if you can produce true MPG for the USA, why not do it here. Be one of the first in the UK to be honest with your customers rather than hoodwink them. Lexus continue to be voted the best dealerships in the UK, they make great cars, so why let yourself down with this blatant manipulation of the so called government figures.

I myself do know the true MPG, so it is not a big issue with me, but I know some unsuspecting buyers are not happy when they do find out the true MPG, surely it is better to be more accurate. Or am I alone in thinking this?

lee789 · August 2, 2015

I believe a US gallon is about 20% less than a UK gallon, so that indicates US owners are being misled too, It is likely they are actually getting about 25 or 26 mpg from a US gallon.

wh05apk · August 3, 2015

With regards official figures they are just that, lexus are not allowed to produce anything else, they are only allowed to publish figures which have been arrived at from a set routine.

They, like all manufacturers are guilty of optimising the cars to produce good figures.

I can't speak about the NX, but I have an IS with the same engine, and with careful diving, not ridiculously slow can achieve figures above the official figures over quite a long distance, so at least with the IS the figures are achievable.

ColinBarber · August 3, 2015

I can't speak about the NX, but I have an IS with the same engine, and with careful diving, not ridiculously slow can achieve figures above the official figures over quite a long distance, so at least with the IS the figures are achievable.

The NX doesn't have the same engine as the IS.

wh05apk · August 3, 2015

Really?

How is it different? I thought they were both 2.5ltr 4 cylinder engines?

Goggy · August 3, 2015

It has been pointed out to me that this is not Lexus at fault, it is the government testing procedure that is flawed. I do accept that, I am not Lexus bashing, or at least it was not my intention to do so, even if it looked like that. I am a huge Lexus fan, having owned one for 4 years and I have another on order. i just feel that something is not right with claimed mpg and everyone knows that, so it's about time it is sorted out. :)

lee789 · August 3, 2015

Tony. Here's the engine spec for NX and IS 300H models.

Lexus NX 300H Engine - The 2AR-FXE ^[8] is an Atkinson cycle variant of the 2AR-FE. It has the same bore and stroke, but the cams and pistons are unique. Geometrical compression ratio is 12.5:1

The large valve overlap leads to a reduction in cylinder charge and reduced torque and power output, but efficiency is increased. This combination makes the 2AR-FXE suitable for use in hybrid vehicles, where peak torque and power demands can be met by theelectric motor and battery.

Lexus IS 300H Engine - The 2AR-FSE is a direct-injected variant of the 2AR-FE. It has the same bore and stroke, but the cylinder head, cams and pistons are unique as well as the fuel management system. Thermal efficiency is about an excellent 38,5%.^[9]

^{Maybe the decision to go with the reduced torque and power supplied by the 2AR-FXE engine in the NX was deliberate, so that it didn't overshadow the performance of the 200T. Who knows, but IMHO it was a bad decison.}