Motorway Mpg

[ChrisCooper]

I have a 2009 2.0TDCI Focus.

My main driving is a 15 mile each way run consisting of a mix of A roads, B roads and a little bit of suburban at each end (including a 10min+ sit in traffic in the morning thanks to roadworks). Normally I get in the mid to high 40s MPG for this run, with the return journey being by far the better of the two. I don't do much motorway driving, but when I do it's usually around 10miles or so, and I find that if recently reset my MPG gets closer to 40, this is running at around 70mph (usually by GPS, so around 74 on the speedo) with cruise control on. I would have expected the motorway MPG to be better, particularly compared to the A and B roads. It's not temperature related as most times when I've been on the motorway I've been up to temperature before reaching them, wheras most normal run is from cold both ways.

I've checked the tire pressures and they are all at the recommended level. I've changed the air filter recently too. Is there anything else that is likely to be effecting the MPG on higher speed runs, or is this just normal? It's a bit disapointing as even my old petrol car would be in the high 30s on motorway runs, and I thought diesels were supposed to be at home on the motorway.

[jamesm182]

Does seem a little low to be honest. When was the last time it had an oil and fuel filter change/service? MPG can tend to dip a little over winter, especially when we all have heaters/lights/wipers etc on most of the time.

[btmaldon]

My petrol does over 40 mpg on motorway driving so yours does look low. My old man came round the other day showing off the fact that his 150,000 mile Megan Estate 1.5 diesel averages 68 mpg. Makes you sick that an old Renault is far more economical than a newer Ford.

[leesheffield]

I have a 2009 2.0TDCI Focus.

My main driving is a 15 mile each way run consisting of a mix of A roads, B roads and a little bit of suburban at each end (including a 10min+ sit in traffic in the morning thanks to roadworks). Normally I get in the mid to high 40s MPG for this run, with the return journey being by far the better of the two. I don't do much motorway driving, but when I do it's usually around 10miles or so, and I find that if recently reset my MPG gets closer to 40, this is running at around 70mph (usually by GPS, so around 74 on the speedo) with cruise control on. I would have expected the motorway MPG to be better, particularly compared to the A and B roads. It's not temperature related as most times when I've been on the motorway I've been up to temperature before reaching them, wheras most normal run is from cold both ways.

I've checked the tire pressures and they are all at the recommended level. I've changed the air filter recently too. Is there anything else that is likely to be effecting the MPG on higher speed runs, or is this just normal? It's a bit disapointing as even my old petrol car would be in the high 30s on motorway runs, and I thought diesels were supposed to be at home on the motorway.

I've heard that using cruise control uses a lot more fuel as the computers are calculating what throttle to use etc. don't know how true it is. i suppose its as said above. the more equipment you have on i.e. heaters cruise, electric windows etc the more power and fuel is needed to keep them running.

[InKontrol]

Check your brakes in case one of them is binding. :)

[theduke]

try it at 60mph i know its boring but my mpg shoots up, is yours 5 speed at 70 the rpm would be a little bit high also turn cc off and anticipate inclines/declines

[ChrisCooper]

Thanks for the replies. I'm going to take it in for a service on Friday as I've had it nearly 2 months now, and when I changed the air filter it was pretty bad so I presume other things need doing. Will get the full oil and filters done, and will get them to check the brakes are not binding, although it does drive freely.

Regarding other loads, the odd thing is that most of my none motorway driving has been mornings and evenings with the lights on and often heating on full blast, but mostly on the motorway it's been during the day.

Have wondered if the cruise control is part of the problem, as I don't normally use it on normal trips as there are few sections where I'm holding a constant speed for more than a few minutes, other than the couple of miles at 40mph through some roadworks (where my MPG tends to do best). Noticed when using it at speed it tends to surge forward and then lift off abruplty, wheras manually controlling the speed I can normally hold it more constant with much smoother adjustments. It's strange as I'd always thought cruise control was more efficient than manually controlling speed. Perhaps it's like a lot of these things where a reasonably skilled and attentive driver can beat the computer. Regarding the load from the CC, I wouldn't have thought that would really make a difference as it's handled by the engine management system, and any additional computing power would be negligable.

[APJ]

Have you tried sticking some redex in and giving it a good thrashing in 3rd gear for a sustained period, might just need a good clear out. I can get high 60s on long motorway run in 6th gear at just below 2000rpm