Typical Is300H Motorway Fuel Consumption

sc489 · December 19, 2014

I'm interested in buying a Lexus IS 300H. My motoring is typically 50% semi-rural and 50% long distance 300 mile motorway journeys at 70mph. What would be the typical fuel economy for these types of driving when driving economically? Test reports suggest I might obtain c. 55mpg for the semi-rural driving but I'm unsure of the realistic fuel economy from the 2.5 litre engine on a long motorway trip where the hybrid drive is unlikely to be used much. Also, what are the typical engine rpm when cruising at 70mph?

Richard1200 · December 19, 2014

Can not help you with the rpm question as I have never taken note of it.

On the fuel consumption --- I do 95% town driving as I am retired, getting about 44mpg although in this colder weather it has dropped slightly. The best I have ever seen on a long motorway drive is low 50's. All I know is my petrol spend is half what I used to spend on my IS250. Beautiful smooth 6 cylinder engine but thirsty.

I have only reset my fuel consumption trip once in 6000 miles. It's on 43.9 mpg today.

ColinBarber · December 19, 2014

if you are actually sticking to 70mph then 55 mpg is possible, maybe 50 mpg with an F Sport or Premier due to heavier and wider wheels/tyres

Tel · December 19, 2014

C.80-85mph I get c.48 mpg but @ 70 I achieve c.58 mpg.---------only look @ the revs in Sport-mode.

Tel

ColinBarber · December 19, 2014

Engine revs are typically low when cruising. There isn't a direct correlation between speed and engine rpm as there is with a manual transmission or an auto transmission which has gone into lock-up. The CVT will rev the engine up or down depending on power requirements at any particular moment.

sc489 · December 19, 2014

Thanks for your prompt replies. Motorway economy as reported is better than I anticipated. How does the hybrid drive achieve such efficiency when the power is being provided mainly by the 2.5 petrol engine during motorway cruising? I'm considering the IS 300H Executive so c. 55mpg seems possible - a significant improvement on 42mpg I get with my current 2.0 petrol Honda Accord.

DJP · December 19, 2014

I think it's because the motor is still supporting the petrol engine. If you drive it "aggresively" then the mpg suffers considerably, but reasonably "normal" motorway driving delivers 50 in my F Sport no trouble.

ColinBarber · December 19, 2014

It is a relatively efficient, high compression, direct injection, Atkinson cycle 2.5l engine. The electric motor will also assist somewhat providing some minor benefit.

The cruise control is also tuned for efficiency and allows a couple of mph flexibility so unnecessary braking doesn't occur on downhills and aggressive acceleration is avoided on minor inclines.

Push it above the speed limit though and the engine begins to work more and economic drops to what you would expect from a normal 3l engine. Conversely get stuck in some 50 mph roadworks and you can achieve 55 - 60 mpg on that stretch.

Steve44 · December 20, 2014

C.80-85mph I get c.48 mpg but @ 70 I achieve c.58 mpg.---------only look @ the revs in Sport-mode.

Tel

I think it's because the motor is still supporting the petrol engine. If you drive it "aggresively" then the mpg suffers considerably, but reasonably "normal" motorway driving delivers 50 in my F Sport no trouble.

How are you two getting 50mpg+ in your F-Sports ?!?

My best ever is 46.5 (tank to tank calculated - back in August), my running average is 41.3 and I'm doing 80% of my mileage on motorway's. Car is now at 12k miles.

My fuel computer is consistently out by +4mpg.

I've tried running in Eco mode and Normal, with and without cruise control and so far my best at 70mph on the motorway is about 46-47 on the car, which is 43-44 calc'd.

This week I did get to the heady heights of 53mpg, driving back from Hayes to Leicester, round the M25/M1 through roadworks and traffic - i probably was only running between 45-55mph the most of the way, as soon as I could increase to 70mph, the mpg started to drop.

At 70mph cruise - 50mpg is all but impossible for me.

DJP · December 20, 2014

My on screen average is c42 mpg, now nearer 39-40 with the colder weather.

My most common motorway journey is 100 miles using Croydon M25/M3/M27/A31 towards but not as far as Bournemouth. Journey average never less than 50.

As I have the wife onboard it's a fairly boring steady middle lane speed. Because I know that's the protocol for the journey I am quite keen on maxing the mpg just for the fun of it. When I'm on my own I suspect my returns would be more akin to yours.

IMO mpg difference between using Eco compared to Normal is negligible and not worth the definite lag in responsiveness. I rarely use Sport, occasionally when an idiot needs education, or when I want to have a but of fun for a few minutes. Unfortunately those opportunities are fairly few and far between.

Sent from my Iphone using Lexus OC

feanor · December 21, 2014

My average is consistently around 45mpg, that is with mainly motorway driving during the week.

Bear in mind my boot is full of work equipment adding a lot of weight at all times, without that I would get over 50 easily.

How the car manages the mileage I am not entirely sure, the electric motor seems to work best at complimenting the engine in maintaining a constant speed. (at motorway speeds). I usually cruise between 120 - 140kph, and rarely use the cruise control, I use manual paddle mode and switch to ratio 6, this seems to provide better results than the cruise control computer.

On a flat motorway section, I can see the system is using both electric and engine, and if I ensure no extra load than just maintaining speed, then I usually have long stretches of 60+ mpg displayed. My best so far is 25 mins driving at 140kph and having 60+ mpg for the entire time.

I find it enjoyable playing with driving style to achieve the best result, increasing speed without extra mpg on any downhill section, and allowing speed to decrease on small uphill sections, all the while the mpg remains the same or gets better.

Sport mode to overtake, or just have a little fun, accelerating away from toll booths etc, it is uncanny how all other cars are left dead.

Or on empty B roads etc, but it all averages out, leaving usually 45-48 on the display. If I drove more economically Id be sure Id achieve 50+

gt03raf · December 21, 2014

been looking at this with interest....

I have an F-sport, with 15.5k on the clock now in 10 months.

I live in Milton Keynes and spend 2- 3 days a week working at home with the odd short journey around town..

It's a killer on MPG as it's 70mph dual carriageway for 1/2 mile then a roundabout.. repeat, repeat, repeat....!

I also head into london a couple of days a week and do the M1, North Circular and then back roads into the office..

I'm surprised by some of the mpg figures being quoted also..

Around MK i get around the 40 mpg mark.... when i'm on the motorway consistently higher bringing my average to 48-52 in the summer, and 44-48 at this time of year.

Interestingly if i fill up on my way out of MK into london i often get between 58 and 62.. 64 is the highest I've seen on arrival at the office..

I've done the brim technique and my on-board reading is very accurate, maybe 1-2mpg overstated tops.

I'm no angel but tbh in commuting hours the cruise control is set to mid 60's as it's difficult to achieve more than that anyway!

My car is almost permanently in eco-mode, apart from the odd flip into sport when i want an overtake out of the way..

after various BMW's and Merc's this is my first Lexus and i absolutely love it..

Andy

Blisteringblue · December 22, 2014

Or just be boring like me, shove it on cruise at around 75 and my mpg is rock steady at 50+. In summer it's closer to 55 than I'm finding now in Winter, but my average from 1st Dec is still currently 50.7 on the clock.

When I work out actual from the company car expenses it will round down to about 47-48 but I'm more than happy with this.

PS. I am about 75% motorway BTW

ColinBarber · December 22, 2014

Also, what are the typical engine rpm when cruising at 70mph?

I specifically looked at this today. On a very slight incline and whilst accelerating very slowly (1 mph increase every 10 seconds) engine revs were around 1,600. When level at a constant 70 mph the engine was at 1,400 rpm.

Gentle acceleration used to keep up with traffic as car pull in and out of lanes never increased the revs over 2,000.

lexicon · December 27, 2014

As stated by others the engine revs are more related to load than speed.

It's possible to travel significant distance at only about 1200 rpm if the terrain is flat.

In the summer, taking it steady but still at around 70mph, I saw 60mpg from Manchester to Portsmouth. Realistically, that's about 56 as the computer is a bit optimistic.

More than any other car I've owned, it's very sensitive to how you use your right foot. Very good numbers are achievable, but will plummet once you start pushing. My work commute (30miles m/way, 15 mixed A-road) can vary by at least 20mpg depending on circumstance/mood/weather.

Over 10k, I've averaged 50.

sc489 · December 28, 2014

Thanks to all for your useful replies. The average of your replies is c. 56mpg when cruising at 70 mph at engine rpm c. 1200-1600 rpm, increasing to 2000 rpm when overtaking. I'l be taking a test drive soon.

The new Mercedes C200 petrol version also appears quite economical. I've been looking at the Mercedes UK Forum. In contrast, the Mercedes Forum is full of topics about people complaining about problems which I don't see on the Lexus Forum!

lexicon · December 28, 2014

You do need to drive one to get to grips with the drivetrain.

The whole rpm thing is quite different to any 'conventional' setup due to it not having any fixed gear ratios.

If you poke the throttle firmly, the revs will spin up to basically maximum and stay there until you ease off.

A lot of people (seemingly) can't get on with this behaviour.

ganzoom · December 29, 2014

We considered the Mercedes C200 petrol before ordering the Lexus. I doubt very much the C200 will get half it's claimed mpg in traffic, which is what most of our driving will be in the IS300H.

Equally the poor reliability of our BMW 3 series has made us very weary of buying another German car. I think most motoring magazine are very biased toward BMW/Audi/Merc. The main complaint of 300H is the noise on acceleration, but in reality it's no worse than any small capacity engine.

Best bit of the IS300H....Since ordering ours in early December, in total I've spotted 4 on the roads, in contrast there's about of the 6 Merc C classes parked in various driveways on our street.....So I'm glad we didn't go for the 'commoners' car :)

Wallace · December 30, 2014

When ours was three days old we took it on a trip to Kent, M54, M6, A14,A11 M25 and M2. I noticed we were only doing 1500 revs at 70MPH and got 52MPG, not bad. It's down quite a bit in this cold weather but still way better than the IS250 Sport we had.

Roscobbc · January 1, 2015

My use is London around and within M25. Had the car 3 months. Now the temperature has dropped economy is around 41 mpg. When weather as a lttle warmer is was up to 43 mpg. But its such a relaxing place to be!

sc489 · January 2, 2015

The economy reported in Post 20 is about 10 mpg less than the previous reports. Do you have a sporty driving style and are you driving a less economical IS 300H model?

Roscobbc · January 3, 2015

The economy reported in Post 20 is about 10 mpg less than the previous reports. Do you have a sporty driving style and are you driving a less economical IS 300H model?

Mine is the IS300H Executive edition. Can't really say that I 'hoof' the car around - generally prefer to use in Eco mode and not drive specifically for economy. Economy for me is much the same city or A road useage. Oddly about the same in mpg no's as my previous 120D Sport Auto!

michaelH · January 4, 2015

Cold weather and new winter tyres have made a big dent in my typical mpg. I was getting around 52 mpg (actual, brim to brim measured) in the summer, but am now getting closer to 44 for the same kind of journey. In the summer, I would sometimes see 60+ on the readout. I never see that now. But its no big deal and no doubt mpg will go up again next summer. The sums of money involved are relatively small, unless you are covering an enormous annual mileage

Rabbers · January 4, 2015

It would appear that increases in consumption are broadly proportionate to drops in temperature.

My consumption over a few days when temperatures averaged around -3°C dropped to 15.2km/l (43mpg) from my

customary 16.8km/l (47mpg). It then dropped alarmingly to 14.3km/l (40mpg) during a week of constant subzero

temperatures which went as low as -10°C. With temperatures having averaged around +4°C over the past three

days, it has crept back up to 16.1km/l (45mpg).

When my consumption increased, it was all the more noticeable considering that my speeds were substantially

lower than usual because of icy roads.

Roscobbc · January 4, 2015

My previous BMW 120D Sport Auto dropped by a similar percentage in the colder weather conditions - our vehicles electrical systems such as lighting, heater fan/electric heated seats will be in greater use and leaving 'systems' on when stationary. It's pay back for otherwise having economical/efficient vehicles.