Real World Fuel Economy

[marrat]

Some very smart people on Priuschat speculate ACC shoots to high rpms to get to speed because it's the most efficient way for the hybrid drive.

[Zotto]

It is only partially true,  engine has better  thermal efficiency only in a range of rpm (in Atkinson engines over 2000 rpm till about 4500), so, it's better to keep revs not too low, nonetheless strong acceleration requires more energy compared to slow increasing of speed, and this is the reason because cruise control is not so good when cruising with many decelerations caused by traffic, reaccelerating costs energy; cruise control is very useful to spare fuel with no traffic, keeping a fixed speed and then requiring a constant energy (at least in flat routes, down ad up hills this is not true but with energy recovering in hybrids what you loose going up you recover much going down). And this is another advantage of hybrids: driving  in lands with many hills you obtain better mpg compared to cars where all energy downhill is lost in heat and brakes consuming.

[marrat]

Why do you assume getting up to the required speed fast is more energy consuming than getting there slower? If what you say is true, it would mean the engineers made a serious mistake.

[Blisteringblue]

93000 miles driven in my IS300h and it's a metronome 48mpg come rain snow or hail.  Probably 75% motorway though.   As Steve says a brisk acceleration and then back off flicking between EV and Petrol.   Always in Normal, there is no point to ECO mode, just creates Lag to me.   If I sit at 70 mph in the summer it will nudge 52-53 mpg, but I tend to sit at 75-77 and it is seriously rock steady 48 mpg.

This is every bit a motorway car for me even though all reviews claim it isn't,   So much so I've just ordered another but a Sport this time.

The 12500 service interval is the only pain for the miles I do, but it's a company car so not really my problem, just comes around a lot sooner than my old diesels.

[Zotto]

About Marrat's question, if it it would not be so the best way to spare fuel should to drive always at full throttle, and you can see it is not true...

The best is to have whole car working at it's best, keeping engine at rpm where thermal efficiency is better, not too low and not too high, and minimizing all losses from transmission, wheels friction and so on.  So,  while low rpm are not good for efficiency, too high one are not good too for all other reasons. So, my suggestion from  a standstill is to accelerate at about 2500 rpm till the speed you like, then release right foot and press again just to keep speed, or if you are trying hypermiling techniques try to have zero electrical current  (energy indicator  at zero point between "charge" and "eco" area); speed will slowly decrease till next impulse given from thermal engine to reach again the proper speed.

[steveledzep]

Just 2 weeks ago I acquired my first Hybrid, an RX450h 2013.  I'm fascinated by the dash graphic and very interesting it is too.  I'm buggered if I'm going to allow it to dictate my driving style !!

[Zotto]

Often it happens, but the positive side of driving an hybrid is that if you keep your previous style will have better MPG compared to a traditional car.

[MONTIMAR]

I collected my new IS 300h 10 days ago. The dealer had filled the tank and after 500 miles the average shows 57.6 MPG since the last fill up. I completed a 75 mile run in ECO mode last Saturday and recorded 64.8 MPG from Leyburn to Scarborough. All A/B roads in heavy traffic so not a fast run but I was amazed how economical it was.

[TechyD]

On 09/04/2017 at 0:47 PM, MONTIMAR said:

I collected my new IS 300h 10 days ago. The dealer had filled the tank and after 500 miles the average shows 57.6 MPG since the last fill up. I completed a 75 mile run in ECO mode last Saturday and recorded 64.8 MPG from Leyburn to Scarborough. All A/B roads in heavy traffic so not a fast run but I was amazed how economical it was.

Wow that's really good going! Mine is 13 days old and I've got 450 miles with a 1/4 to go, trip says 45.3 at the moment. I've not been using ECO mode though I have to say, throttle is just so lethargic to input I've not adjusted to it yet! I'm planning on staying in one mode over a tank to see how they each compare!

[paulrnx]

Is the only reason that people buy an IS300h for its economy or its perceived economy? Driving say 12,000 miles per year at 50mpg would require 240 gallons of fuel. Doing the same miles at 40mpg would require 300 gallons of fuel. At about £1.20 per litre of fuel in the uk and 4.5 litres of fuel in a (UK) gallon, that's a difference of about £325 over a full year or about £27 a month. Call it £1,000 over a 3 year period. Over the same 3 year period a 36,000 mile IS300h will lose I'd guess about £15k although we could probably argue whether it was only £12k or as much as £18k. Then you pay £hundreds per year on insurance, an average of £300 per year on servicing, four new tyres in that time too and then incidentals on top. Fuel economy doesn't really matter that much. It's always interesting to see what is achievable but it ain't the be all and end all of motoring.

[Rabbers]

1 hour ago, paulrnx said:

.... Fuel economy doesn't really matter that much. It's always interesting to see what is achievable but it ain't the be all and end all of motoring.

Speaking for myself, having "gone hybrid" after several years with IS250s (which I liked for many reasons of which low fuel consumption

was certainly not one), first with an IS300h and now with an RC300h, I remain dazzled, even if the novelty has worn off after four years,

by the fact that my spending on petrol, without my consciously aiming for economy (which I am congenitally incapable of doing for more

than a few km at a time, if at all), is literally half of what it previously was.  While I fully understand that a halving of my fuel bill has not

dramatically influenced overall costs, I do nevertheless regard it as one of the most important of several factors that add to the pleasure

of ownership.  In short, an economic nice car is surely better than an uneconomic nice one.

 

[NemesisUK]

Coming from the CLS55 with its 16mpg to the RC300h with a current 47mpg has made me a stranger at my local petrol station.

The staff sent a letter of condolences to my wife, thinking i must have passed away! 

[paulrnx]

I once had a BMW X5 4.4 V8 and worst I saw was 14.9mpg over a 150 mile journey. Went like stink for a 2.2 tonne SUV

[rayaans]

1 hour ago, paulrnx said:

I once had a BMW X5 4.4 V8 and worst I saw was 14.9mpg over a 150 mile journey. Went like stink for a 2.2 tonne SUV

Thats not too bad - my 2nd gen RX300 did 16mpg

Was it worth it?

Hell yes - the smoothest car Ive ever driven, which is saying something  - it was like rubbing your appendages on silk!

[Tel]

My 2017 is definitely so much smoother & appears to engage the Battery mode more readily in heavy traffic.

I only drive in Sport Mode & in my previous car averaged c. 48 mpg with 52 mpg on long Motorway high speed runs--perfect.

in the Jura Mountains, close to Switzerland with 4 adults in the car, I got 25mpg going up to the Top & 58mpg returning to the Valley floor.

Cannot wait to see if the new car is marginally better.

Tel

First longish Motorway journey c.92 miles Nottingham to Worcester South & return.(Sport) 

Monday c. 0600hrs South took 105 minutes @ 55mpg

Return c.21.00hrs North took 80 minutes @ 48 mpg

Venice to Verona cruising @ 130 mph in my Isf achieved 18.5  mpg (average over 3 years 26.5 )

Tel

[Steve44]

2 hours ago, Tel said:

My 2017 is definitely so much smoother & appears to engage the battery mode more readily in heavy traffic.

I only drive in Sport Mode & in my previous car averaged c. 48 mpg with 52 mpg on long Motorway high speed runs--perfect.

in the Jura Mountains, close to Switzerland with 4 adults in the car, I got 25mpg going up to the Top & 58mpg returning to the Valley floor.

Cannot wait to see if the new car is marginally better.

Tel

First longish Motorway journey c.92 miles Nottingham to Worcester South & return.(Sport) 

Monday c. 0600hrs South took 105 minutes @ 55mpg

Return c.21.00hrs North took 80 minutes @ 48 mpg

Venice to Verona cruising @ 130 mph in my Isf achieved 18.5  mpg (average over 3 years 26.5 )

Tel

Tel, what techniques are you using to get that kind of mpg?

Speed you are doing? Cruise control or manual control? Higher tyre pressures? Managing acceleration? Pulse and glide etc etc

i can get barely 45mpg (same as previous car) and I'm convinced it must be down to personal driving style.

i agree the car EV/battery management is better now than before.

[Casa1862]

1 hour ago, Steve44 said:

Tel, what techniques are you using to get that kind of mpg?

Speed you are doing? Cruise control or manual control? Higher tyre pressures? Managing acceleration? Pulse and glide etc etc

i can get barely 45mpg (same as previous car) and I'm convinced it must be down to personal driving style.

i agree the car EV/battery management is better now than before.

Same here, only ever get about 42 mpg, 45 maybe on a run, I think I drive "normally" I don't drive with millage in mind. I also don't understand how some people say the get 30 to 40k on a set of tyres, I'm about half that!

[Tel]

Steve,

I use cruise control in the UK for all Motorway Traffic Flow Control Systems set @ 52mph for a 50 limit.I accelerate into the fast lane & sit there c.80 to 85 mph.In France I do exactly the same & get + 2mpg due to less congestion & 400 mile hops.

In Italy,Summer temperatures,I get 38-40 mpg sitting there @ 90 to 95 mph but if I slow to my UK speed c.58 mpg.

Tyres are 36psi in the UK,39 in Europe.

I am excellent @ smooth braking/ lane changing that my 1999 200 IS Sport reached 45k. miles before requiring new pads / tyres when the norm was 10k. according to Lexus Leicester.

Seriously I drive my F-Sport as my ISF & only miss my Supercar's rapid acceleration joining German Motorways & its fabulous brembo Brakes.

I drive smooth, but never Hybrid &, have always driven in Sport Mode.

Always quote the cars computer.

Terry

 

[BigChange]

Tel, why the different tyre pressures UK and (Continental) Europe ?  I thought 36 covered everything.

[paulrnx]

18 hours ago, rayaans said:

Thats not too bad - my 2nd gen RX300 did 16mpg

Was it worth it?

Hell yes - the smoothest car Ive ever driven, which is saying something  - it was like rubbing your appendages on silk!

I should have added I was towing a 1400kg caravan too. Awesome performance even with a caravan on the back. Not quite so good on the mpg front though. I'll have to try the silk thing now 

[MONTIMAR]

I collected my new IS 300h 10 days ago. The dealer had filled the tank and after 500 miles the average shows 57.6 MPG since the last fill up. I completed a 75 mile run in ECO mode last Saturday and recorded 64.8 MPG from Leyburn to Scarborough. All A/B roads in heavy traffic so not a fast run but I was amazed how economical it was..

I have been driving a Toyota Auris Hybrid for 2 years and get 70MPG in the summer months on a proper fuelly with 80 MPG showing on early morning fishing trips to York. When I first started driving the car 58 MPG was normal until I learned that using Battery power through 30/40 MPH limits made all the difference to fuel consumption and stopped me getting speeding tickets. A double saving.

I drive my Lexus the same way. It's a question of maximising the Battery power in the right places. I have no experience, yet, of driving either car on a motorway as the nearest motorway is 50 miles away. I'm planning a couple of trips to Devon and Bristol in the summer which will give me a few answers.

[Tel]

Peter,

Sustained high speed increases the tyre footprint to bulge much greater & you compensate for this by raising the pressure by 10% or more dependant upon the Tyre Manufactures Recommendation.

Terry

[olliesgrandad]

My phone app indicates that my last tankful exceeded 44 Mpg. Suspect that the warmer weather is helping as I do similar journeys most weeks (mixed motorway /urban). 

 

[Steve44]

On 4/12/2017 at 0:01 PM, Tel said:

Always quote the cars computer.

Terry

 

Which one?  After reset (When do you reset)? After Start? After Refuel?

[Steve44]

On 4/12/2017 at 11:45 AM, Casa1862 said:

Same here, only ever get about 42 mpg, 45 maybe on a run, I think I drive "normally" I don't drive with millage in mind. I also don't understand how some people say the get 30 to 40k on a set of tyres, I'm about half that!

I got 55k out of the rear Bridgestones on my previous IS300h, and 70k out of the fronts!  Just do lots of long motorway miles. Plus the Bridgestones are so hard.