Improving my MPG on an E70 2010 plate - sorted i think

[Smatty]

Right, for my sins I visited the lexus garage to have a look at the rx450 Love my X, but the cost of fuel is really starting to irk me again and getting 23mpg round the doors is making it worse.

Anyway, I challenged the figures that Lexus are claiming, and the salesman told me he had just been on a training course with Lexus on how to max the mpg performance, as loads of customers are kicking up a stink. He said it was basic stuff, but required the driver to change his/her driving style and make use of the eco mode. The eco mode is a button that switches the motor from petrol to electric. His basic description of the new driving technique is to drive like you've got a manual gear box - as you approach round abouts, hit eco mode for approach and pulling away. If you see clear road ahead of you, hit eco mode. Clear road ahead to a junction, hit eco mode etc.

'its just like hitting neutral in a normal car, cruising, then pulling away. The big benefit is the electric motor helping you pull away'.

Then it hit me, the X auto gear box has a tiptronic type mode between D and N.

So, for the last few days I've been using the auto box as a manual box and improved my 'round the doors' mpg from 23 to circa 27+mpg - and its quite nice not just sitting back and tootling about.

I'll keep doing this for a wee bit, see if its not a freak occurence, but if its not then hey ho, could be on to a winner.

Oh, and I got 33mpg on a run to Derby this week too

[chetalien]

iteresting but will it affect the engine in anyway. what happens to engine oil consumption?

[Turks]

I'm not sure what this would do to the Auto Box, Diffs and Torque Converter. I've always been a little worried to roll along in neutral in an auto and 4x4.


Turks.

[Chompers]

I could be talking out of where the sun doesn't shine, but doesn't rolling in neutral actually use more fuel than leaving it in 'Drive' with your foot off the throttle. Thick I read this somewhere before that the ECU stops sending fuel to the engine when in 'D' and no throtttle but keeps fueling while in 'N' to keep the engine running as if it was stationary. Just a thought. Deffinately an advantage when at traffic lights/stationary to put 'N' but as Turks said, not sure about 'N' while driving along the road

[AW8]

I don't think you should do that.

The RX450 isn't coasting in neutral in eco mode.......it is using electric motors to supply the energy.

If it was safe & easy to reduce mpg that way manufacturers make transmissions that switch to neutral when coasting.

RWD automatics shoud be rear suspend tow recovered.

FWD automatics should be front suspend tow recovered.

4x4 automatics have to be straight lift recovered.

I apreciate you still have engine on but automatics are different than manuals in being hydraulic I would also be concerned re the 4WD system.

Perhaps someone with an engineering background will explain things better or in more detail.

[chetalien]

I dont think I would employ such a technique for a few short term gains might be doing some damage somewhere unless some techie comes and says its ok.

[535dboy]

You wouldn't find me doing that-if it was ok to do it BMW would have programmed it in to their cars to help them!

Like chompers I believe on some cars it can use more fuel as the cars fuels the engine with no drive (ie neutral) so it keeps running whereas running with gear engaged means the wheels are turning the engine over

[acideraser]

Here is my 2p: as far as I know coasting can save fuel indeed but on manual and if you do it downhill.
My dad used to do it 25 years ago but I don't think it saved that much fuel it's not recommended by manufacturers.

regards

[Smatty]

Oh well, that fecks that up

[petert]

Coasting in neutral can save fuel on a carburetted car because a carburettor never shuts off the fuel supply completely and pulls less fuel when coasting than being in gear. Fuel injected systems however can shut off the fuel completely when there's no load on the engine so its better to stay in gear. Shifting into neutral means the fuel injection system has to supply enough fuel to keep the engine at tickover.

Anyone elese remember when SAAB used to fit freewheel devices that were for coasting? Before my time (first car was a 1972 SAAB 99 but that didn't have the freewheel)

Peter T