Running D5 hard
 

In my attempt to improve fuel efficiency, for the past year I have been driving my xc70 very cautiously.

Watching some videos on carbon buildup/blocked EGRs and stuck swirl flaps, I am wondering if I am doing more harm than good.

Is it wise to work the car hard every now and then? If so, is there a recommended method to this?

As a matter of interest
What fuel consumption are you hitting?
I have a 2008 D5 SE Sport AWD
I’m getting about 35mpg but she does get a few hard spurts (Polestar upgrade)
I’m told. They need a blast every now and then.

Good fuel is the way for a clean engine.

My own personal experience is i run my S80 on premium diesel. It runs around 50mpg and the engine oil stays remarkably clean. I change it at 9K mile intervals half the Volvo interval and it is just about going black by then. It’s the cleanest engine I’ve ever owned going off this. All my other and previous Volvos go jet black instantly but this is the exception. The only difference is this has run on premium diesel throughout my ownership when purchased with 30k miles on. I thought I’d run this one on premium more as an experiment than anything else but hardly scientific but I’ve just sort of kept on with it.

I’d say just carry on how you are, but frequent oil change and good fuel and you’d be fine don’t worry.

Agreed. Good quality fuel and regular servicing including the fuel filter is the way to go, as well as regular motorway drives.

I don't put supermarket fuel in my car. Whenever I do, it sounds like a tractor and doesn't do anywhere near the economy that I'd get from the same fill up in Shell or Texaco.

So the place that you get carbon buildup if you don't run a diesel hard, is at the top of the cylinders and around the valves. I've seen plenty of videos where they have done engine teardowns to prove this.

Additionally injectors can become clogged and/or leaky prematurely.

A hard acceleration onto a motorway junction or dual carriageway whenever the opportunity presents itself is very beneficial to a diesel.


I'll do 120mph+ all the way across Germany in my XC70 when I do a European trip, for quite a while after the engine runs fantastic, it really smooths out the idle

Some interesting points.

I am getting around 28-30mpg on average.

Serviced every year, although I only changed the fuel filter for the first time on the last service.

Only use esso diesel as I have a esso card.

I do have 2 bike racks on the car st all times. Guess that will add some wind resistance.

I have starred using redex (as suggested by ny father in law). On every other full fuel fill up

My car gets whatever is cheapest diesel, gets the nuts revved off it either by hard acceleration or engine deceleration (manual), just generally thrashed if there's a nice A/B road to safely play on + motorway driving and oil changed on 18k or thereabouts. Returns roughly 37mpg and runs absolutely fine at 213k.
Probably explains why when I changed my belts at 70k they were close to failure but they didn't so happy days.

Is that 30mpg just around town?

In my case:

I only ever use Premium Diesel at all times (Shell and Total / Aral when in continental Europe) - unless unavailable / unexpected refill.
My all-time fuel consumption in my signature below. It's been variable depending on our circumstances, however in the last 8 months I started regular bi-weekly commute (so make 1,000 miles a month). In the last couple of years it was only local driving - so more like 1,000 miles in a year :cool: except when holidaying on the continent somewhere.
I do not drive it hard, I think - as evidenced by rear pads wearing faster than front ones - and cannot really remember when exceeded 3,000 rpms, might be incidental in the first year of my ownership when I forgot to change the gearbox from manual to auto! But do not drive it exactly slow either...
Engine, exhaust & emissions were commended as exceptionally clean in the past during MOT/Servicing and as I know remain as such.

Its a mix. I'd say 70% is town and 30% motorway/Dual carriageway etc.

If I reset the mpg and then drive on the motorway it's around 38-40mpg, depending how I'm driving.