Do Not Sell My Personal Information Jump to content


Fuel Efficiency


Recommended Posts

Hi, I've had my 05-plate 400h SE-L for slightly above 6 months now. I have driven it in both winter and summer and on most occasions done brim-to-brim fill-up based comparisons (the OBC has consistently overstated the truth by 2mpg). The best I've managed so far is 34mpg. The worst (27mpg) was during the February snow period when the car was driving mostly on petrol at very slow speeds. The more you get the car to coast, the better the mpg, as while coasting the car doesn't run on the engine. Also, the car runs subtantially longer on the Battery alone (providing you keep a light right foot) once the engine has warmed up sufficiently. On open country roads (40-50mph roads) I tend to use the cruise control quite a lot. That improves the mpg quite dramatically. Cruise-control mpg is the best in the 50-70mph range. I have seen no evidence of the mpg being better at above 70mph speeds in motorway driving. But then, mine is only one of the hundreds of 400h's cruising the roads of the UK.

Link to comment
Share on other sites


Even brim to brim comparisons can be inaccurate.

It all depends on how patient you are at the pump. (Or indeed whether or not you use the same pump every time or yet again depending on the ambient temperature, etc etc.) The difference between the first click off of the pump and petrol actually overflowing over the edge of the filler neck can be up to 10 litres!!!

A more accurate way is to keep a log of fuel bought and miles driven over, say, 5000 miles to iron out the different inaccuracies. But then you only get an overall figure which doesn't tell you consumption for different types of journey in different temperatures.

I still say the biggest variable is the right foot!!!!

JBP

Speaking technically, you are absolutely correct: using the SAME pump at the SAME station and filling at the SAME time of day with weather conditions etc. all are factors (IE: you can get 'more' fuel on a cold winter morning than at the same time during a summers day) - BUT these variations you are talking about are minimal and even with them taken into account, this remains a far more accurate than relying on the OBC alone.

More important is using the SAME type of fuel (IE: Tesco own vs. Shell) than using different brands and quality.

The spreadsheet is another way to average out, over a period of time, costs and get a more accurate figure - just depends how far in depth you want to go. I stand by brim-to-brim filling for everyone to use as a valid comparator.

Link to comment
Share on other sites

I tend to use the cruise control quite a lot. That improves the mpg quite dramatically. Cruise-control mpg is the best in the 50-70mph range. I have seen no evidence of the mpg being better at above 70mph speeds in motorway driving.

Using cruise control is definitely better for MPG and the 'best' speed for economy is 56MPH. Anything really over 70MPH and you are using disproportionately more fuel per MPH of speed.

Link to comment
Share on other sites

Even brim to brim comparisons can be inaccurate.

It all depends on how patient you are at the pump. (Or indeed whether or not you use the same pump every time or yet again depending on the ambient temperature, etc etc.) The difference between the first click off of the pump and petrol actually overflowing over the edge of the filler neck can be up to 10 litres!!!

A more accurate way is to keep a log of fuel bought and miles driven over, say, 5000 miles to iron out the different inaccuracies. But then you only get an overall figure which doesn't tell you consumption for different types of journey in different temperatures.

I still say the biggest variable is the right foot!!!!

JBP

Speaking technically, you are absolutely correct: using the SAME pump at the SAME station and filling at the SAME time of day with weather conditions etc. all are factors (IE: you can get 'more' fuel on a cold winter morning than at the same time during a summers day) - BUT these variations you are talking about are minimal and even with them taken into account, this remains a far more accurate than relying on the OBC alone.

More important is using the SAME type of fuel (IE: Tesco own vs. Shell) than using different brands and quality.

The spreadsheet is another way to average out, over a period of time, costs and get a more accurate figure - just depends how far in depth you want to go. I stand by brim-to-brim filling for everyone to use as a valid comparator.

Don't forget tyres low rolling resistance or not, pressures, AC on/off, windows/sunroof open/closed, vehicle weight, vehicle clean/dirty......the list goes on :lol:

In the end you bought a 3-3.5 litre 4x4.......who gives a jot about consumption? I must admit when I first bought my RX I was interested for the first month, more so to work out what real world running costs would be, but since then I just throw in the splash and drive it, end of story :P

Link to comment
Share on other sites

  • 3 weeks later...
...driving in a 'hybrid style' I got almost 38MPG (i have a picture of it somewhere)

The ONLY way of talking reliable figures would be to use figures from a brim-to-brim fill up. Otherwise relying on the OBC you will find that you will also ahcieve 99.9MPG in certain situations - if you beleive that, then well I guess the moon is also made out of cheese and the Earth is indeed flat.

Talking OBC is pointless IMHO.

ok done it your way and got 36.8 MPG that was driving carefully but not totally in a hybrid style for the whole time, this was over 253 miles, 31.17 litres, unless my calculation are wrong?

Link to comment
Share on other sites

ok done it your way and got 36.8 MPG that was driving carefully but not totally in a hybrid style for the whole time, this was over 253 miles, 31.17 litres, unless my calculation are wrong?

Well I'll be the first to say it, I stand to be corrected :) Your maths is correct mate.

Link to comment
Share on other sites


I've not any calculations as such as I'm only on my second tank of fuel now. I collected the car from the dealers with a "full tank", but don't know whether it was brimmed or not. Anyway, I got 350 miles on that tank doing my normal commute, before the fuel light came on. It then took 53 litres to brim the tank from there (don't know the exact tank capacity).

Now on this refuelling, I got to 220 miles with half a tank left (computer saying 31.9mpg). Doing the same route day in day out in my RX350 I would get 250 miles to the tank with the climate control on, or 280-290 if treading carefully with it off.

In the real world then, the RX400h is undoubtedly giving me better economy back-to-back with the RX350 and I'm not going to the pumps so often, but the car's performance can be identical. I say "can be" because I'm finding (ironically) slightly addictive driving the RX400h in a hybrid style e.g. backing off the gas at 30mph, then stepping on the amps! On some roads, I can cruise at 40 mph on electric only, and I still never see the traction Battery charge go less than about 60%. Sooner or later, I am going downhill and getting some energy back, ready to help push me up the next one.

Looking forward to doing a long distant cruise soon when I can see how it does on a motorway drive. Obviously the hybrid element does well for economy on the urban commute.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



×
×
  • Create New...