Disappointing MPG

[Tatsfield]

The system calculates the mileage left until empty against what the engine is currently doing, so if you change driving from fast cruising to slow town crawl the computer recalculates the estimated mileage to empty. Best not to rely on it as you cannot guarantee how you will drive the last 10% of the tank. If it told you how much fuel was left to the ml, you'd still have to do a calculation to guess how far it would take you and you'd probably do no better than the computer. It's very useful on long distance motorway driving when you are continually holding the same driving profile and need to know which upcoming fuel stop is going to be optimum.

[apersson850]

The car estimates the remaining range based on how you've driven the last 30 km.

I did a 500 km motorway (mainly) trip last Friday. My XC70 D5 automatic AWD reported 6.2 l/100 km. I think that's pretty decent.

[Tatsfield]

I'm a little perplexed about the 30 km resetting as I've noticed my estimated fuel reserve drop or raise more frequently than that, especially in town crawling mode, but I wouldn't swear to it as it's from memory and mine is long past its sell by date!

[Ant B]

Originally Posted by MCFastybloke

Can expectations be higher for the 2012 cars/212 bhp?

In my experience, yes; my 215ps V70 will return 50+ mpg at 60-ish mph, high-40s mpg at 70mph, mid-40s at 80mph, even low-40s at steady 90mph.

I’ve even had nearly 800 miles out of a tank (once; basically 2x 400-mile round trips from Manchester to Reading, pre- and post-rush hour so minimal traffic and specifically driving economically), usually get 600-650 out of a tank, mix of one 400-mile motorway trip, plus usual commuting, school run, shopping etc.

So yes, the later twin-turbo cars are better, I think...

[apersson850]

It's not an every-30-km-reset I'm talking about. It's a moving average, based on the last 30 km.
How frequently they update I don't know. Maybe they keep track of the last 30 km, one by one. Which would imply that as soon as you have driven one more km, the new estimate is based on that km and the previous 29. The one before that is forgotten.

Thus if you drive 30 km, all the time with the consumption "1", then hit the accelerator and drive one more km with the consumption "2", then your range will be estimated based on a consumption of "1.03" (i.e. 31/30).

When I bought my XC70 2012, Swedish car tax was based heavily on CO2 emissions, which are directly related to fuel consumption. The 2012 215 hp version of D5 had a tax that was roughly 65% of what they wanted for the 2011 205 hp version. So quite a lot happened there.