Terrible Fuel Economy Figures

[AmateurDomestic]

Hi,

We have just bought an '08 RX400h at the beginning of Jan. Since then on urban driving we are getting average MPG figures of somewhere between 14 and 21 mpg. We have owned the RX 300 and we used to get 21-23mpg so we are really baffled by this. I took a note of the mileage just to check back and we did 280 miles on a full tank till the fuel light came on. Using my calculations, a full tank is 17 gallons so maybe a 2 of that is in reserve. So that would be 280 miles on 15 gallons which is 18.6 average which checks back to the figures the car is giving me. I understand that when it is cold (as it has been recently) then it can use more, and that we live up a steep hill, but surely the braking on the way down should regenerate enough power to help.

Is anyone else getting such poor MPG on their car, I'm just worried that there is a fault with the hybrid system and we only have 2 more months on the warranty.

[Duncan Roberts]

Hi,

We have just bought an '08 RX400h at the beginning of Jan. Since then on urban driving we are getting average MPG figures of somewhere between 14 and 21 mpg. We have owned the RX 300 and we used to get 21-23mpg so we are really baffled by this. I took a note of the mileage just to check back and we did 280 miles on a full tank till the fuel light came on. Using my calculations, a full tank is 17 gallons so maybe a 2 of that is in reserve. So that would be 280 miles on 15 gallons which is 18.6 average which checks back to the figures the car is giving me. I understand that when it is cold (as it has been recently) then it can use more, and that we live up a steep hill, but surely the braking on the way down should regenerate enough power to help.

Is anyone else getting such poor MPG on their car, I'm just worried that there is a fault with the hybrid system and we only have 2 more months on the warranty.

The lowest by far that I have ever read here. Clearly if you are using it for deliveries in central London or wherever that might happen but I would suggest taking it back to the dealer. 'Search' here also to learn the sort of normal values - 27-33mpg (or slightly better) experienced but diagnosis on the vehicle not the web would be best from both a practical and legal point of view.

[AmateurDomestic]

Thanks for your reply, we have a trip to Cambridge next week so we can see what figures we get for that, it may be that I am just using it as a run around at the moment.

[rhosneigr]

Before my last service at the begining of this month the mileage figure on the computer read out never fell below 28.5 mpg. I had a Battery change on the service which obviously resets the computer, and at the moment the readout is 23.1 mpg. I know the weather is exceptionally cold and I've not done a large mileage mainly around town but I hope any changes in the ECU settings when disconnecting the Battery are not permament or will it relearn my style of driving.

[Beejay]

My Battery was changed yesterday and my mileage was around 29.5/31.5 but is now [on similar routings] showing 22.5. I guess I have to do the reset trick.

[rhosneigr]

What is the reset trick? I'm hoping that with a few more miles and the weather due to get a little warmer the consumption with get better.

[ColinBarber]

you can search for ISC learning procedure. It will reset the idling speed on certain vehicles if the Battery is disconnected. However I doubt it is the issue here, it shouldn't make that big a difference.

If you turn off your heater is the engine cutting out when stationary? and when the engine is idling is it at normal revs? If yes then there is no reason to perform a reset

[rhosneigr]

All seems fine with engine idle and the cutting out. I'm putting it down to the lack of mileage covered since the service not allowing a proper calculation.

[Hut49]

It's going to depend entirely on the type of motoring you're doing. Driving a mix of out-of-town roads with a fair amount of accelerating to 50-60-70mph, then in the winter season, in my 2009 Rx400h, I typically get 22-24. Burn a tank on enthusiastic use of acceleration and a motorway thrash or 2 and I have been sub-20. If most of the driving is in town at 25-35mph average speeds, where the hybrid stands a chance of making a net contribution to fuel economy, then, again in the winter, I'll typically be seeing 27-29. In the summer my corresponding figures are going to be 32-35 in town, 28-32 out of town and 22-24 on a thrash. You can optimise fuel economy by learning the hybrid driving technique and this does make a noticeable difference but I'm hopelessly undisciplined and always in a rush...

[AmateurDomestic]

Thanks for all the replies, I think it may just be because I am not going far enough, most of my trips have been under a mile, drop off then come back up a hill. It seems to be do better when we are on flat ground and going further so we can use the momentum.

[rhosneigr]

What was the mpg readout showing when you first bought the car or had it been reset.

[AmateurDomestic]

Hi, it was on 24mpg since the last refuel and had done 100 miles to be delivered from Bedford to Surrey on the M1 and M25. I didn't think this was terrible, but not great either.

[DanD]

Thanks for all the replies, I think it may just be because I am not going far enough, most of my trips have been under a mile, drop off then come back up a hill. It seems to be do better when we are on flat ground and going further so we can use the momentum.

In the current weather and under these conditions, you will be relying essentially on the petrol engine. The hybrid system will be of little use until the car has reached its normal operating temperature. You should find that the fuel economy is much better on a longer trip.

[SAD69]

Hi,

We have just bought an '08 RX400h at the beginning of Jan. Since then on urban driving we are getting average MPG figures of somewhere between 14 and 21 mpg. We have owned the RX 300 and we used to get 21-23mpg so we are really baffled by this. I took a note of the mileage just to check back and we did 280 miles on a full tank till the fuel light came on. Using my calculations, a full tank is 17 gallons so maybe a 2 of that is in reserve. So that would be 280 miles on 15 gallons which is 18.6 average which checks back to the figures the car is giving me. I understand that when it is cold (as it has been recently) then it can use more, and that we live up a steep hill, but surely the braking on the way down should regenerate enough power to help.

Is anyone else getting such poor MPG on their car, I'm just worried that there is a fault with the hybrid system and we only have 2 more months on the warranty.

You are using US measurement of 17 gallons = 65 litres. UK conversion factor is 0.21997. Therefore 60 litres (less reserve 5 litres) will be 13.2 gallons or 21.2mpg for 280 miles. Still not good though. I had RX400H before and mostly used in the city. I had around 25mpg for 5 years I owned it (never reset the counter).

[AmateurDomestic]

That's not to bad then, I have tried to stretch it's legs a bit more and the MPG seems a bit more favourable, hopefully should improve with the weather.

Still an amazing car, but we sold the old RX300 because of the terrible fuel economy so we are hoping for at least a slight improvement.

[brucey72]

In the summer I get almost 30mpg and winter it drops down to 28. The car is used for the school run, tesco's and running the kids about! when I purchased the car Lexus said 35 mpg but you would have to drive everywhere downhill and push the car back up for those sort of figures! lol :P

[mburstyn]

So I have now owned my '08 RX400h for a week. My daily run of 18 miles is almost entirely on a 50 mph restricted road after a 1 mile side street approach. So getting onto the main road and setting the cruise control to 50 has enabled me to get just over 37 mpg on each direction.

[Duncan Roberts]

So I have now owned my '08 RX400h for a week. My daily run of 18 miles is almost entirely on a 50 mph restricted road after a 1 mile side street approach. So getting onto the main road and setting the cruise control to 50 has enabled me to get just over 37 mpg on each direction.

Jolly good!

[brucey72]

I don't know how you've got those figures! you must of treated the throttle like your crown jewels! lol :P

[Barrybazz]

I'm averaging 31 on mixed town and fast A roads/odd bit of motorway driving generally.

When I tried really hard I got 33 and when I stopped trying at all I got 28 - I was thinking it's not too shabby for a 3.3 litre

[Unity]

My journey is a commute around a small market town in the morning for about 25 minutes and then a 15 mile A-road journey at 40-60mph.

In the summer I get 35-36mpg pretty consistently and in the winter about 31mpg. I haven't reset the trip computer since July and it is now reading 33.5mpg having covered ~6000 miles. If I'm really careful I've had 38-40mpg but you really have to try hard to get that!

I think you need the right kind of journey to get the most out of a hybrid car. A bit of urban is fine as long as its had a chance to charge up during braking etc. Where I used to live, I just crawled around a small (congested) town to do the school drop off and get to work, and in the winter struggled to get ~22mpg.

[mburstyn]

38.9 on Friday! It's not difficult as long as you keep the cruise control on - sometimes i hardly have to touch the brake/accelerator for most of the 18 miles

[HASSELBLAD]

Hi,

We have just bought an '08 RX400h at the beginning of Jan. Since then on urban driving we are getting average MPG figures of somewhere between 14 and 21 mpg. We have owned the RX 300 and we used to get 21-23mpg so we are really baffled by this. I took a note of the mileage just to check back and we did 280 miles on a full tank till the fuel light came on. Using my calculations, a full tank is 17 gallons so maybe a 2 of that is in reserve. So that would be 280 miles on 15 gallons which is 18.6 average which checks back to the figures the car is giving me. I understand that when it is cold (as it has been recently) then it can use more, and that we live up a steep hill, but surely the braking on the way down should regenerate enough power to help.

Is anyone else getting such poor MPG on their car, I'm just worried that there is a fault with the hybrid system and we only have 2 more months on the warranty.

That is simply appalling and something is very wrong.

I sold my 2008 RX400h last October and it had NEVER averaged under 31mpg in 5 years of ownership. On non Motorway 100 mile trips, it readily reached 39mpg and if I put my mind to it and used the hybrid system to best effect, 42 mpg was always there for the taking. I used to get 26mpg dragging a one ton Ifor williams trailer!

Take it straight back to the seller=======lots of things could be wrong and maybe your hybrid energy retrieval system is just not functioning. If you need help ( and it sure sounds like you do) go to Lexus at Guildford and ask for Colin Searle. He's a man who knows what he's talking about.

Assuming that you already know how to get the best out of a Hybrid, check engine condition,tyres, brakes, handbrake, exhaust recirculation system etc, as for any car. Check how far the car will run just on its fully charged high voltage Battery. Watch the display to ensure the traction Battery is being charged up and that the SAME level of charge is there the next morning.

I assure you, far better consumption is achievable.

Good luck and take a peep at my earlier exchanges(late 2012) on the RX450h.They might help.

My one year old RX450h is averaging a genuine 32mpg at the moment and has logged (still on the display) a best 120 mile trip of 55.1mpg.

[The Swede]

I would not say it is appalling straight away.

An RX300 and RX400h should not be very different on longer journey's / motorways as here the hybrid system does not come into play.

Where the hybrid really should cut fuelconsumption is on short distances / town driving.

Two questions that pop to mind:

1. How often do you notice the car drives purely electrical (if at all) ? If it never drives in electrical mode, then something is either wrong with the car... or with your driving style.

2. Did you adapt your driving style to driving with a hybrid? If you hit the accelerator always with your "clumsy boots", then the car will straight away go "Shoot, I need the petrol engine, he/she wants to accelerate fast". ...

It has nothing to do with how fast you drive afterwards. And I hereby just draw on the experience of seeing my girlfriend driving. She just cannot move a car on a hint of revs, let it crawl when parking or smoothly get of the line. The accelerator is more an on/off button with her. If she'd drive a hybrid, the electrical engine would never ever engage

[kalibur]

My two pence worth when I got my RX400h (3 weeks) ago average mpg read 29.5. First 70miles of motorway at 70-80speeds I got a lousy lower 20s mpg, stopped at the services noticed one wheel was at 21psi I pumped that to 32psi and saw an immediate improvement. Last weekend a drive from Woking to Edgware (London) I averaged 31.5 mpg M25, M4 exited at Heathrow got back A41, M25 way. When doing 50-60 I get 34ish.

On my 15minute trip to work steeps/slops temp -3 to 5C I am averaging about 25-27mpg (keep in mind its winter) the first 5minutes i get below 10 mpg engine heating up, 5-10minutes I get about 20-30mpgs and the last 5minutes of 15 I get between 35-40mpg. Average speed of journey 5m/h to 35m/h over a 4-5mile trip.

1 - What I have learned is when the engine is cold it will come on and stay on till its warm enough, it doest care how much your charge you have only exception is when you're coasting.

2 - Driving slow isn't the magic trick, the trick is knowing how to talk to the CVT thus get to the speed you want then foot off gas 0.5 second then engage cruise control or resume a light foot on gas, this allow the CVT to pick a higher gear (ratio) at lower RPM and if torque is needed the Battery compensates at all speeds at lower speeds power tends to alternate. If you drive up to a speed and maintain at that speed without taking the foot off gas 0.5secs or put it in cruise, chances are it will stay in a lower gear and the hybrid wont kick in because the car thinks you're still accelerating and have not reached your cruise speed yet.