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I have been the proud owner of an 08 Plate RX400h SE-L for 3 months now and absolutly love the car however !!!!

I am dissapointed in the MPG I am getting and am concerned there could be a problem with the Hybrid system or am I just expecting too much.

I am averageing 26.5 MPG with a mix of city traffic and quiet country A roads.

The tyre pressures are correct and I am using BP not supermarket fuel.

I am also driving like a light footed grandad and lifting off the gas whenever possible.

Looking at the fancy power graphics my Battery very rarely goes into green and has never shown completely full, also I can be driving at 20mph on the flat with good Battery charge but still the engine kicks in.

Is this normal or should I book in for a check as I understand the Hybrid System has a 5 yr warranty ???

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The engine should kick around 25mph so it seems it may want to charge the Battery.

Also on the motorway you will get around 34mpg. So 26 on city driving is not too bad. Is that the current MPG or the AVG tank MPG?

Best thing you can do is go to your dealer and get the Battery tested for peace of mind and while its still in warranty!

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I have only once had a full house on the Battery charge indicator and that followed a 2 miles plus downhill run. Fuel consumption is very dependant on ambient temp so you should see an improvement in warmer weather.

May be worth doing a search for the Isc Learning Procedure. I did it once following an aux Battery replacement and it seemed to work.

It may not work exactly as the procedure in the posting though.

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Yes if I were you would do the ISC reset,which needs to be performed if the main Battery has been fully drained or replaced. If you google you should find the reset and it only a couple of minutes to perform the procedure.

Agree that my did not go exactly as description.Power meter did not go as described.

When I got my 56 car.I got the dealer (non Lexus) to replace the Battery as part of the deal and was initially getting mid 20s to the gallon. After performing the reset procedure I now average between 30 to 33.

Agree cold temperatures will reduce fuel consumption,but think from what you have said that you should be getting a better MPG.

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Agree cold temperatures will reduce fuel consumption,but think from what you have said that you should be getting a better MPG.

Actually will reduce the mileage and increase the consumption, but that is just to clarify, what you meant. Otherwise I also agree with the suggestions so far.

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First time I've heard about an ISC reset, I changed my Battery about 4 months ago and since then from about 31mpg I now seem to hover around the 29 mark. Not a great difference but my driving style/commute hasn't changed. I would be interested in the reset (if it's easy to do!) Have searched the forum but can't find any info, does anyone have a link please? I am also aware that as the weather turns the mpg is likely to lessen. Thanks :hohoho:

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Thanks for your advise,

I will Google the ISC reset proceure or might pop into my local Lexus (Sheff) to see if they can do it for me.

Will advise if this makes any difference over the next few weeks.

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This is it.

The instructions are as follows -

This applies to the 2006 Highlander Hybrid also.

Note that you can probably perform the procedure yourself.

The scan tool mentioned in the procedure checks the coolant temperature to make sure it is at full operating temperature and checks the engine loading to make sure the load is sufficient to charge the Battery and finally checks the status of the ISC learning parameter. It is not necessary to monitor these parameters if you do the procedure carefully.

1) Make sure the vehicle is fully warmed up. Do the procedure immediately following a long drive that runs the engine (highway speeds are best - not long gliding stealth runs at low speeds with the engine off). This will insure the coolant temp is at FULL operating temperature - it is not necessary to actually measure the coolant temperature if you warm up the engine sufficiently and don't let the engine shut down too long and cool off before doing the procedure.

2) With the vehicle stopped and in drive, press firmly on the brake to keep the vehicle from moving and then step on the accelerator while watching the power meter (to the left of the speedometer). Press down on the accelerator to keep the needle between 1/2 and 3/4 up the scale. You will find that the engine management system will automatically limit the engine load no matter how far you press down on the pedal so the amount you press is not critical as long as it is either 1/2 scale or to the engine's self-limiting load value. Keep the engine loaded for a full 30 seconds but not longer than 40 seconds (this procedure brings the hybrid Battery up to a maximum state of charge - if you watch the Battery symbol, you willl see it tick up to a "full" display).

3) Shut off the engine and place it in park

4) Wait 5 seconds.

5) Turn the ignition key back on to display "ready"

6) make sure the A/C and heater system controls are set to off

6) Lightly step on the accelerator pedal until the engine starts -then immediately take your foot off the accelerator and let the engine run until it stops by itself.

This completes the procedure.


I've done this procedure successfully a few times now (ran my Battery dead once, and disconnected another time when trying to reset the NAV system)

The only thing I noticed (and it didn't seem to matter) was that I could not get the power meter anywhere near 1/2 to 3/4. No matter how far I depressed the accelerator, the engine management system would not let the power climb even 1/4 way. Everthing else worked as stated though.

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