Real Mpg

[mikesands]

Just thought I would record that my real consumption was 28.5mpg whilst the computer shows 29.5mpg (UK gallons). The buttons on the computer reset and the odo trip meter were pressed at exactly the same time. Whilst I would have been happier if the error had been the other way, it is at least within about 3% and on other cars I have had it's been as much as 10%

Mike

[Duncan Roberts]

How did you record your supposed "real" consumption?

[ColinBarber]

It seems to vary with my vehicle. Normally between 5% and 10% the wrong way, it never underestimates.

I don't always record my fuel ups but my averages are:

http://www.fuelly.com/driver/colin10086/rx400h

[mikesands]

That's not bad Colin,

I will aim to get mine to that in normal driving. The 28.5 was achieved by really molly coddling her. Discovered the dealer had put less air in the left side tyres than the right, so I have evened them all up to 36psi - will see if that makes a difference, then wil try the ISC reset after this tankful

Duncan - fillup to fillup. Always do it with any vehicles I have. I'm a bit anal about it really

Mike

[mikesands]

Second tankful seems to be running about 2mpg better. Maybe the evened out tyre pressures, but it's also been a bit warmer weather.

Mike

[DanD]

28.5 matches what I average with mine. This is also whilst being "careful", although with aircon switched on.

I have never achieved the heady 32/33mpg reported by others on this forum. Having said this, I bought the RX to enjoy it and my view is that if economy is your priority the RX is probably not the car for you.

It can be fun trying to maximise fuel consumption though, I have to admit... ;-)

[mikesands]

It looks like this tankful is going to end up back at the same (computer) reading as the first 29.5 - which is really 28.5 - however I have been driving more normally this time, so I still think the tyre pressures have made a bit of a difference. In normal driving my LS430 used to return 22mpg for the same driving pattern. However, it would return a genuine 30mpg on a long run at 75-78mph which the RX is definitely not achieving.

My pal has just bought an identical RX400H and he drives at 80-85mph on a run and I see his average is 30.9 which includes about the same town and semi urban miles as me.

Mike

[mikesands]

identical to mine (18inch and Bridgestone Potenzas)

Mike

By the way this is a reply to ColinBarbers question 'does he have 17" or 18" wheels and what tyres?' which I have got as a notification by email but is not showing in the thread - wierd.

[DanD]

30.9 at 80-85mph!?

I guess this might be achievable at near constant speed and on a flat run.

Would you know if he relies heavily on the cruise control and whether he leaves the aircon switched on?

[mikesands]

He says that he gets 33mpg if he resets the computer and then drives at 80-85mph on a motorway. If I do that on mine I suspect it would be around 25-26mpg. He may of course be being economical with the truth.

Mike

[DanD]

I suppose that it does make sense. If you were to reset the computer just before getting onto the m-way, and then drive at more or less constant speed, it is likely you would achieve decent mpg.

I tend to reset the computer when I fill up - if I remember! - so the 28.5 I achieve is an average over trips that vary in distance, road type, etc etc.

[ColinBarber]

I don't believe you would achieve 33mpg at 85mph for any length of time. Maybe on a nice flat with the wind behind you but 20+ miles at that speed and I would expect the mpg to drop below 30.

We also have to consider indicated or real figures? The speedo always reads over so at 85mph you are really only doing around 80mph and an indicated 33mpg is probably 31mpg.

[mikesands]

yeah I think you are right Colin. i will ask him to do the experiment properly

Mike

[mburstyn]

I think I have posted on this subject before, but anyway. My daily run in my 400h of about 18 miles involves a 1.5 mile rat run to a dual carriageway and a 16.5 mile 50 mph ride to my destination. I reset the consumption meter at the outset and am regularly getting 40+ mpg as the enclosed photo will show. I leave the cruise on for the whole run only occasionally switching off to slow down or resetting to speed back up to 50. With a light right foot this is not difficult, but it's very easy to have a heavy left foot!!

[DanD]

Is this down hill with the wind behind you!?

[teejaybee]

Time to be a bit controversial here....we've all got Lexus's, we know they're a premium marque which brings premium costs. Part of these costs include of course petrol, it's prettty well documented about the range of mpg the RX400h can experience. In my view, and it is only my view, I bought mine because I wanted it, whether I get 26mpg or 36 mpg to me is neither here nor there. I just get on with it and fill it up when I need to. It's nice to see what other people are getting mpg-wise but at the end of the day is it really such a big issue? Just enjoy the car for what it is, after all if a difference of a few mpg is a concern maybe a Lexus wasn't the best choice? I'm sure I'll open up a can of worms here but isn't that what forums are all about? People's views?

[Duncan Roberts]

Time to be a bit controversial here....we've all got Lexus's, we know they're a premium marque which brings premium costs. Part of these costs include of course petrol, it's prettty well documented about the range of mpg the RX400h can experience. In my view, and it is only my view, I bought mine because I wanted it, whether I get 26mpg or 36 mpg to me is neither here nor there. I just get on with it and fill it up when I need to. It's nice to see what other people are getting mpg-wise but at the end of the day is it really such a big issue? Just enjoy the car for what it is, after all if a difference of a few mpg is a concern maybe a Lexus wasn't the best choice? I'm sure I'll open up a can of worms here but isn't that what forums are all about? People's views?

TJB is absolutely right, if you really need to fret about the last 2/3 mpg in use then you have bought the wrong car. It is big, heavy, powerful and that has a significant bearing on consumption and it is totally predictable. Mine varies from 27-30 depending upon the weather, the type of roads and and how I need to drive but that consumption is quite irrelevant beside the pleasure of owning and using it over the last 75,000 miles from new.

[mikesands]

The main reason I'm checking and asking the questions is to establish if the car has been set up right, because if not then I would ask Lexus to take a look at it. What this thread has shown me is that my car is probably pretty average and therefore probably set up right.

I must admit the car is growing on me, and I've just come from a LS430 (deceased). Apart from road noise from the rear, this car is at least as quiet as the LS. Considering the suspension is springs and the car's CofG is considerably higher than the LS, the handling is miraculous. But the most surprising thing to me is that the RX400H seems to have much more zip than the LS. If you want to drive the LS430 fast and get some seriously rewarding thump in the back acceleration, you can, but IMHO only in manual mode. Drive it in auto (even Sport mode) and the delay between asking for power and getting it, is far too long. The response on the RX is instant - just like it used to be on my GS300.

Mike

[mikesands]

..... mind you I do miss the smart key, and wafting air con :D

Mike