VVRX

BertL, To be honest when driving on the open roads and freeways I pretty much drive as you do, but locally when afforded the opportunity, I take advantage of the unique mileage characteristics of my RXh.

DunWkg

Bert, I'm in that minority too. Perhaps a subset of that minority, the lead-foot subset.


Original poster, my best tank ever was 5-10 mph below every posted speed limit combined on interstate, highway and in town...32.9 mpg

GRussell

For the record, normally I'm a very fast driver, though more so in my convertible. And for those times I feel like employing hypermiling techniques in the 450h, I'd never do it with other cars behind me. This question is more about route planning. I agree that it's almost impossible to control all the other variables (hills, temperature, etc) that people have mentioned here... I'm just saying that if we remove them from the equation, there must be an optimal speed that the 450h likes to go at.

Perhaps I can blame the longer than expected break-in period on this SUV for my curiosity. Knowing that I wasn't getting the promised mpg at first, I really started paying attention to mpg display. I said "For the amount of money that I paid for this vehicle, it will get it's promised EPA ratings, or it's going back". I know there are plenty of reasons to buy a Lexus, but the SUV with the highest MPG ratings was one of my higher ones.

Thanks again to everyone who replied.
Best,
-Glenn

Alpy64

Glenn
the promised mpg the car manufacturers (not only Lexus but all of them) are presenting are only of pure commercial interests particularly since the 2008 crisis and the oil price growing up which people are now looking closer. Figures given are based on tests in closed construction on specifi machines/equipment but which does not represent real and concrete driving conditions outside (never and never). You can reach the values but difficult to reproduce them continously and regulalrly (particulalrly considering difference of temperature in winter and summer in Europe, Canad and US, etc. as long as the hybrid system is sensitive with external temp.

The question about the "optimal speed" must be seen from 2 points of view:
1- when you drive by using oil motor
2- when you try to combine oil end electrical motors

It's quite difficult but I can suggest an answer. When I drive on a road quite flat, flat countryside for simplifying the context, I display the instant consumption information on the dashboard and then I try to find the optimum speed and pressure on the pedal. Ideally when external conditions are there, I can assume that the optimal consumption displayed is running around 5 to 6l/100km or if you prefer from 47mpg (US) to 40mpg (US) @ 90 km/h or 56mph or so. If you increase a little bit your speed (same driving conditions e.g. traffic, weather, wind...) you can reach approx. the same figures for consumption but when the speed is increasing you will see that the instant consumption info is increasing as well.
Now going down to low speed you will see that you cannot decrease the consumption very much below 5 - 6l/100 (47mpg (US) to 40mpg (US) when trying to lower you speed to optimise again the speed... the electrical motor takes the advantage.

GRussell

Hi Alpy64-
Yes, I agree... Having the electric motor kick in at times makes this question harder to answer. My question applies to when the electric motor is not assisting (your case #1) as I think that electrical assistance factor will average out over the long haul. I'm also thinking of traveling on a flat surface, at a constant speed, over a long distance.

Hmmm... If true, this would answer my question. 56 mph sounds a bit high for optimal consumption though. Can you tell me where that is displayed? I don't remember seeing it.

Thanks,
-Glenn

kitlz

I got my best mileage (34 MPG) on a flat highway going no faster than 60 MPH. It was just after the break-in period of 5K. I don't drive them often though. Mostly it's hills and varying speeds under 45 MPH. Now at 20K and with eco mode on I'm averaging 28 MPG which is pretty impressive with the spirited way I drive. I may turn off eco mode the next time I fill up to see if it makes any difference.

Alpy64

Hi Glenn
it is displays by using the small button on the steering wheel (right side) and then you can display the current instant consumption (a bar running from left to right when you accelerate). You can easily estimate the current consumption when the bar is in the middle that it is approx. 5l/100km (in european metric system for instance).

Now even though you drive with engine (and you think that it is not assisted by electrical motor (the front one), it's not true because in fact, electrical motor periodically runs and stops alternatively which basically explains itself why the 450h is a low consumption vehicle.
In addition, if you have the chance to drive in the mountain (going up), if you can drive steep road and quite sportively with the RX you can think that the batteries will be fully charged, just because you always use engine... unfortunately not! You will see that when arrived your batteries are almost "empty". This means that when driving in the mountain (going up) electrical motors are running together with the engine to save petrol.

Other point: when driving on a flat road legal speed (let's say around 56mph; French legal limit on the roads unless other speed limits are mentioned) I never use the cruise control to reach my consumptions because sometimes if you can use the relief of the roads you can reach 40 to 50 and even 55mph with only the electrical motors just by relaxing the pressure on the right pedal and to find the minimal pressure to run electrical motor without activating the engine (particularly when on down roads not very ).