GS450h MPG... why would you buy a 3L Diesel

[st4]

I have a Lexus CT bought new in 2016. very rarely managed true 50-55 mpg in the motorway
my previous GS250, a brilliant vehicle, usually managed an average of 25-28
 
the 3-litre twin turbo AWD 740d, manages a true ( by true a mean checking amount of fuel divided by distance) 44 mpg in the motorway and an average 40.8mpg on the meter ( for comparison, Lexus CT has an average 46mpg on the meter, mostly driver in the city though)
 
so yet, for high mileage cruising, I still think a big diesel is better

Diesels are good on fuel no doubt but that saving can be quickly offset by a repair needed due to the complexity of the thing. I’ve owned six in total. 4 were totally reliable and 2 needed repairs (exclusively due to being diesels) that brought the per mile cost extremely close to a v8 petrol for the two. Both the unreliable ones were v6 OM642 Merc diesels and they’re by no means the worse. The 5 cylinder Volvo I had was the best on fuel (never did less than 48mpg on a run) and the best sounding and the one I miss the most.

How did you drive your GS250 to get such low mpg. I’m averaging over 35mpg in mine and I’m no slouch.


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[Initial P]

Not bad for a run:

 

[Spacewagon52]

On 5/30/2018 at 8:54 AM, st4 said:

 

Diesels are good on fuel no doubt but that saving can be quickly offset by a repair needed due to the complexity of the thing. 

 

This is a very valid point. The most economical car I have owned was a Skoda Octavia diesel, never went below 50mpg - but when the turbo went so did my overall economy.

[Northern_Si]

One thing I love about my GS450h is the Jekyll and Hyde personality of the car. Drove from Bolton to Hull yesterday sticking to the speed limit, it is the best cruiser I know (also did 47mpg which isn’t bad considering the big hill I drove over). Coming back I drove via Scarborough and Whitby mostly in Sports mode, making progress on the country roads including some satisfying (and safe) overtakes of up to 3 cars at a time on some of the straight inclines (I love the power on tap)... finding myself on the Leeds ringroad before returning to the M62 (maybe using the shortest route wasn’t the best option) ... final indicated MPG ... 43MPG. 

[Linas.P]

I would like to note the MPG you 50.3 quoting - is short term and not say figure for entire tank. From historic values it seems that long term figure would be closer to ~40MPG.

Advantages of diesel are simple - if you never go into town and only do highway miles you can easily get 70MPG+. So if you do a lot of miles (20-30k/year) and all you miles are predominately on motorway you can still save with diesel car.

In UK diesel advantages are minimal because of outdated speed limits from 60's, but elsewhere in Europe with more reasonable 130-140km/h limits (~90MPH) diesel start to make a lot more sense, because batteries becomes simple additional weight at ~70MPH+,where wit hdiesel you can do 120MPH and still get reasonable fuel economy. In UK you can expect to get say 40MPG in 450h and 55MPG in diesel, in Europe difference is even bigger ~ 32 vs. 52MPG.

Obviously, what that means is there are no advantage having diesel in UK if you do combined urban and extra urban driving and hybrid clearly comes on top in purely urban driving.

[Vlady]

3 hours ago, Northern_Si said:

final indicated MPG ... 43MPG. 

Music to my ears! 🙂

I don't have the car yet, hopefully will be picking it up this coming weekend but I was worried that the mpg is going to be not great, I don't do big mileages but 60% of them on motorway and it is good to know that the car can be economical on it as well! 🙂

[Northern_Si]

18 hours ago, Linas.P said:

I would like to note the MPG you 50.3 quoting - is short term and not say figure for entire tank. From historic values it seems that long term figure would be closer to ~40MPG.

Advantages of diesel are simple - if you never go into town and only do highway miles you can easily get 70MPG+. So if you do a lot of miles (20-30k/year) and all you miles are predominately on motorway you can still save with diesel car.

 

47MPG was the indicated consumption when I filled it up after 550 miles.  Depending on the kind of driving I'm doing, I'm averaging about 42 to 47MPG a tank.

If you can find me a 3L, 260BHP diesel which can easily do 70+MPG on the motorway, I'll be really impressed.

From my own experience of touring France and Spain (averaging 5k miles a year) in my previous MB E350CDI and my current GS450h... the MB only did about 2MPG better overall than my Lexus.  I guess my driving style is suited to a hybrid.

Just for comparison.  These are the figures from the Honest John 'Real MPG' statistics.

• BMW 5 Series F10 (2010-2017) 530D Auto - 39.2MPG
• Audi A6 (2011 on) A6 3.0TDI 245BHP - 40.4MPG
• Jaguar XF (2008 - 2015) V6D - 36MPG
• Mercedes E-Class W212 (2009 - 2016) E350 CDI - 36.9MPG
• Lexus GS (2012 on) GS450h - 39.1 MPG

 

[Northern_Si]

17 hours ago, Vlady said:

Music to my ears! 🙂

I don't have the car yet, hopefully will be picking it up this coming weekend but I was worried that the mpg is going to be not great, I don't do big mileages but 60% of them on motorway and it is good to know that the car can be economical on it as well! 🙂

You need to learn to drive a hybrid on the motorway.  Aggressive driving and the heavy use of the loud peddle will cause the MPG to plummet.  Large gaps and gentle use of the brakes are your friend for decent MPG.  

Also sunny days help as for some reason, it doesn't like the rain.

[st4]

You need to learn to drive a hybrid on the motorway.  Aggressive driving and the heavy use of the loud peddle will cause the MPG to plummet.  Large gaps and gentle use of the brakes are your friend for decent MPG.  
Also sunny days help as for some reason, it doesn't like the rain.

No car likes the rain. Standing water puts up resistance so more fuels needed.

My non hybrid gs250 seems to average around 37mpg true. The e350cdi around 40mpg true. There’s not much in it.


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[Northern_Si]

8 minutes ago, st4 said:

 

No car likes the rain. Standing water puts up resistance so more fuels needed.

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From my own experience, it just seems to affect my hybrid more.  I guess the more resistance the less the car can use the electric motors to supplement the power at a constant speed.  I always find it interesting to watch the how the electric motor kicks in on slight inclines to stop the need for increased revs.

[Vlady]

3 hours ago, Northern_Si said:

You need to learn to drive a hybrid on the motorway.  Aggressive driving and the heavy use of the loud peddle will cause the MPG to plummet.  Large gaps and gentle use of the brakes are your friend for decent MPG.  

Also sunny days help as for some reason, it doesn't like the rain.

From my experience every new car you buy be it diesel or petrol, auto or manual needs your driving adjusted. My neighbor bought Nissan Leaf and said it totally changed his way of driving.

I am surprised the car doesn't like rain, I thought may be cooler air is better for the engine but may be it is to do with bigger tire resistance against the water.

 

[Linas.P]

5 hours ago, Northern_Si said:

• BMW 5 Series F10 (2010-2017) 530D Auto - 39.2MPG
• Audi A6 (2011 on) A6 3.0TDI 245BHP - 40.4MPG
• Jaguar XF (2008 - 2015) V6D - 36MPG
• Mercedes E-Class W212 (2009 - 2016) E350 CDI - 36.9MPG
• Lexus GS (2012 on) GS450h - 39.1 MPG

These figures are combined (urban and extra urban) and I believe that is correct. Going back to my previous post - I stated:

• hybrid wins in the city hands down
• there are no advantage of diesel over hybrid in combined cycle (which seems to be proven by above figures)
• diesel only better if you do a lot of miles and they all are on motorway

I never said diesel car can do 70MPG combined with ease, I said it can do extra urban with ease.

[Linas.P]

5 hours ago, Northern_Si said:

You need to learn to drive a hybrid on the motorway.  Aggressive driving and the heavy use of the loud peddle will cause the MPG to plummet.  Large gaps and gentle use of the brakes are your friend for decent MPG.  

Also sunny days help as for some reason, it doesn't like the rain.

Avoiding any braking is key for fuel economy. Which means one needs to predict situation in advance to avoid unnecessary braking, that is especially true with heavy cars (generally any Lexus). You can cover very large distance just on inertia using no petrol and if you predict traffic in front of you correctly braking can be avoided all together. 

Accelerating sharply doesn't actually hurt fuel economy (especially in CVT) assuming you don't spin the tires and don't brake after reaching desired speed.

[Ten Ninety]

8 hours ago, Northern_Si said:

From my own experience, it just seems to affect my hybrid more.  I guess the more resistance the less the car can use the electric motors to supplement the power at a constant speed.  I always find it interesting to watch the how the electric motor kicks in on slight inclines to stop the need for increased revs.

I agree that wet roads affect hybrids more. However, I'm not sure that is to do with Battery power - I actually suspect it might be because some of the biggest economy gains in a hybrid come from maximising time spent coasting with the engine off, whilst not using Battery power. That sweet spot is hard enough to find in dry conditions - in the wet it's downright elusive because each time you lift, the extra drag of the wet road will slow you down more rapidly, meaning you have to get back on the throttle to provide some more thrust.

By contrast, a comparable diesel or petrol engine will be running the whole time anyway, happily torquing through puddles without a second thought, so the difference between wet and dry is likely to be less significant. There will be some impact from the extra rolling resistance, but not the same extent as a hybrid.

That's my theory, anyway!

[Ten Ninety]

5 hours ago, Linas.P said:

Accelerating sharply doesn't actually hurt fuel economy (especially in CVT) assuming you don't spin the tires and don't brake after reaching desired speed.

I have found that's only true up to a point, although I suppose it depends on what you mean by sharp. Brisk acceleration up to a cruise definitely yields better economy than crawling at a snail's pace, because you get to coasting speed quicker. However, if economy is your aim then I find that it's best not to push all the way to the top reaches of the power zone when accelerating. If you properly floor it, that triggers more battery assistance which then has to be paid back later in the form of using fuel to recharge the Battery. I think there might also be a more aggressive timing profile that kicks in when you're really going for it which sacrifices economy for power, but I'm not sure about that - I read about it years ago in the Prius and can't find a reference to back it up now.

[Vlady]

For a start I have a 3.0ltr diesel and I averaging 35-38mpg with my driving and I don't drive fast, most of my commute is to/from work, if Lexus can do same I will be happy as knowing you have all that power under the bonnet is reassuring.

Reading all the above gives me different way of thinking on how the hybrid works, I thought is actually charges the Battery while braking - didn't BMW had something called Regenerative braking but tbh I am not sure how that works exactly either!:) So the more you coast the better, I like accelerating fast to a speed limit and then just cruise.

Anyway, can't wait to drive it again, I hope I will get the car this weekend! 

[Linas.P]

15 hours ago, Vlady said:

Reading all the above gives me different way of thinking on how the hybrid works, I thought is actually charges the battery while braking

It charges Battery in various conditions, one of which is braking. That is because electric motor in Lexus doubles as alternator. It charges when cruising as well, when electric motors are not in use.

@Ten Ninety actually accelerating on electric power would be more efficient then on petrol. I do agree however that accelerating hard would cause different cam profile (not surprising considering engine is VVTI) and thus just throw the petrol at increased rate. I think my comment was more general and not specifically focused on GS450h, variable valves simply throws.. well too many variable to work with. Point I tried to make is that hard acceleration on it's own should not waste fuel, braking or especially braking after accelerating hard does. That is literally the purpose of the brakes - convert kinetic energy into heat.

[Ten Ninety]

7 hours ago, Linas.P said:

 

@Ten Ninety actually accelerating on electric power would be more efficient then on petrol. I do agree however that accelerating hard would cause different cam profile (not surprising considering engine is VVTI) and thus just throw the petrol at increased rate. I think my comment was more general and not specifically focused on GS450h, variable valves simply throws.. well too many variable to work with. Point I tried to make is that hard acceleration on it's own should not waste fuel, braking or especially braking after accelerating hard does. That is literally the purpose of the brakes - convert kinetic energy into heat.

Whilst I agree with your overall point regarding acceleration not being inherently harmful to economy, I don't think you're right about acceleration using electric power being more efficient, assuming we're talking about the Lexus/Toyota system. My understanding is that the battery power isn't 'free'. It has to be paid back later, at the expense of more fuel. There are considerable inefficiencies inherent in first transferring Battery energy into acceleration, and then petrol into engine power into electric recharging. Those inefficiencies mean that you are likely to need to burn more fuel overall, compared to if you'd avoided the Battery kicking in at all during your 'brisk' acceleration. 

From what I understand, the battery's primary purpose is to help fill the torque gap that comes from the Atkinson cycle engine, to allow the car to pull off and operate at low speeds without stalling. Whilst the battery does, of course, kick in to add power at other times, I think this is to aid driveability (and potentially safety) rather than economy. I imagine that is why 'milkfloat mode' is generally spurned by the most committed hypermilers - you might save fuel whilst you're running on Battery but you end up using more later on when the Battery has to recharge again. The use of the regenerating brakes is, according to those who seek maximum economy, similarly problematic. The received wisdom there seems to be that you gain more from allowing the car to coast (i.e. a light touch on the throttle that holds off the regen but doesn't invoke power), than you do from any extra 'range' the re-gen allows because of those inefficiencies at each stage of the process. 

I'm not arguing for the sake of arguing, but as a saddo who gets pleasure from mpg rather than mph these days, I do take a keen interest in this kind of thing. If you have time to expand on your reasons for why you say electric is more efficient, I'm always ready to learn. 🙂

[Vlady]

Jay, I was lost after word WHILST! 🙂

 

[Linas.P]

@Ten Ninety I cannot claim for sure, especially when it comes to specific model, so you might be right. It not true that electric motors are only used to complement petrol engine (like say in La Ferrari), you can drive Lexus GS450h (and presumably most other hybrids) on electric power alone. Especially, in start stop traffic and that is specifically the way to maximise your MPG on hybrid.

My understanding  (in general) is that electric power is always more efficient then petrol.. that is inherently why we use hybrids to reduce fuel consumtion - electric energy is harnessed as byproduct of using petrol and hence entire system is more efficient + electric motors are almost 100% efficient, very little friction or heat is generated, torque and power comes instantly etc. Contrary, petrol power is very inefficient (ICE engines gets at most ~50% thermal efficiency) and then has to go trough gearbox, shafts etc.

You probably right to say that electric power isn't always "free", however most of the time it is captured from what would otherwise be waste energy e.g. regenerative braking. Even when it is generated from fuel, that is more efficient then using same fuel for propelling the vehicle (again that is inherently why hybrid is more fuel efficient).

We need to separate 2 issues here. 1. Cam profile changes under hard acceleration which increases fuel consumtion (completely possible and probably true). 2. electric motors kicks in, that is as well true, but that actually reduces the fuel consumtion in comparison where only the engine powers the wheels.

[Britprius]

Perhaps surprisingly the hybrid system works better in a front wheel drive car such as the Prius or CT200H. It would also be more efficient in a four wheel drive vehicle where regen could be gained from all four wheels. The problem with rear wheel drive hybrids is that there is only so much energy that can be recovered before the rear wheels begin to lock up particularly in the wet. This effect is much reduced on front wheel, and four wheel drive vehicles.
The Toyota/Lexus hybrid system reverts to mechanical braking at any sign of a wheel under rotating or if the car is rolling in neutral.

It must be remembered that the hybrids get all there power from petrol. Using EV or milk float mode uses more fuel. This is because of the losses involved in turning engine power to the generator produces a loss. Turning the 3 phase electricity into a DC charging voltage produces a loss. Using the electricity to charge the Battery produces a loss in the chemical reaction. To reverse this chemical reaction into electricity produces a loss. To turn the DC Battery voltage into 3 phase AC produces a loss, and finally using that electricity to turn the electric motor produces a loss.
It would be much more efficient to use the engine to drive the wheels.

The hybrid gains when energy that would normally be lost when costing or braking is recovered for re use. There is another time when using the engine to drive the wheels that allowing the engine to produce more power than is needed for this. The excess can produce electricity to charge the Battery allowing a wider throttle opening with less pumping losses within the engine. Thus making the engine run at a more efficient level than it normally would.

John

[Spacewagon52]

I had hoped to learn something about hybrids but I am now more confused! However, I do believe hybrids are the future.

[Northern_Si]

I still feel very smug overtaking on the motorway on the decent of a hill with the ICE turned off.    When VW/Audi drivers talk about their valve deactivation technology, I do like to point out mine has similar technology and shuts down all 6 when not required.

[Ten Ninety]

22 hours ago, Britprius said:

Perhaps surprisingly the hybrid system works better in a front wheel drive car such as the Prius or CT200H. It would also be more efficient in a four wheel drive vehicle where regen could be gained from all four wheels. The problem with rear wheel drive hybrids is that there is only so much energy that can be recovered before the rear wheels begin to lock up particularly in the wet. This effect is much reduced on front wheel, and four wheel drive vehicles.

Interesting - I hadn't really considered the RWD impact on regen but of course it has to be the driven wheels which are 'braked' by the regen system. Fair play to Lexus - they've done a good job of tuning this system as it doesn't feel any different from FWD hybrids in use - I'd have thought braking just the rear wheels when lifting off on a corner would unsettle the car but it really doesn't seem to.

Also, nice work on explaining what I was trying to say about losses in a much clearer fashion!

[Vlady]

On 5/29/2018 at 8:57 PM, Glover said:

 

Just watched it; brilliant!

I didn't know or expect a GS to do that! This is great, beautiful! I wouldn't do that to my car but it nice to know it can be done!

Do you think they had to disconnect all the electric restrictions on the car to do that? Is there actually a button that can switch off all of it so you can have some skidding fun, on a private road of course. :)