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IS300h mileage test different speeds.


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Had to drive 175 miles to Dublin and  175 back on Monday.
Just me in the car plus a full size spare wheel which I always bring on long journeys.
Apart from about 20 miles of urban traffic, this is all motorway. Official speed limit in Ireland is 120kph = 75mph.
Going to Dublin put cruise control at 100kph (62 mph).
Coming back at 120kph (75). There was a stretch of about 8 miles on motorway in both directions with limit of 60kph due to roadworks.
Weather was nice at about 12C, sunny, little wind.
Going at 100kph 57.3 mpg
Returning at 120kph 52.3 mpg.
I think this dial consumption can have about 3mph subtracted as I found this on a full-to-full test before.
So, 13 mph produces a 5mpg difference.
Car is three years old with only about 18000 miles done.



 

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I am getting about 42mpg on a 7 mile morning and evening commute. I think it’s into mile 3 before it starts to get warmed up so it has a lot to do in 4 miles to get back the fuel lost on cold starts.

i have had it on longer runs doing up to 48mpg but have not consistently broken 50mpg in mine yet. 

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Interesting.. On thursdsay, i did a return journey to North London from Leicester  just over 211 miles..  It  was showing 57,8 mpg, I did not think it was possible on an F-Sport.

It was a full tank when i left Leicester Sainsburys ( Fosse park)

i think i could have got it higher, because i remember seeing it at 60.4mpg when i got to London.. but on the way up i had to do more hard accelerstion a number of times..

Currently, i'm still on 53.4mpg on the same tank of fuel..

 

My point being that . anything up to 70-80mph, its not the actual speed that determines the economy, but the speed of the engine in RPM..

Hard acceleration will always reduce fuel economy because you are putting load on the engine suddenly.. Either in normal/eco mode gentley accelerate to desired speed then keep at contant speed or in sports mode  quickly get up to speed to desired speed  and keep at the constant speed then change back to eco/normal.  Key is not to always do constant change of speeds i.e accelerate

So on the motorway i use cruise control snd when i check the RPM in sports mode i see its at round 1500rpm..  unless it's going u hill hence rpm goes higher..and uses more fuel... i somestimes stop cruise control and use gentle throttle to not let the rpm rev too higher, of course balancing the speed you need to go at to climb the incline.. When i use cruise control i sometimes use up/down setting to slwo slow down speed of car if I'm xarching car in front too far ( my cruise ciontrol does not have radar control). I think the key is therefore to keep at the optimum engine rpm ( i think between 1000rpm-1750rpm) for best fuel economy. that is my experience..

 

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