Particle filter cleanout but back to square one?

[Beemer2]

My 2007 V70 D5 180HP Geartronic was down to an average 23mpg as I was only running around town for several months (I know wrong vehicle for that). I took the advice read here for doing a particle filter clear-out. Namely after the engine was warm I switched to manual and travelled down the motorway for twenty minutes at 3000rpm. Did the same on the return journey which probably was not necessary.

The result was that after arriving home and of course returning to auto transmission I was able to travel the same local journeys for two weeks at a new average mpg of 29.

After this (today) the average mpg is back down to 23mpg so I am writing to see if anyone has an explanation for the sudden return to the lower figure?

The engine does have the expensive Shell oil after a service 6 weeks ago

regards,

Beemer

[jp11]

What expensive shell oil do you have?

[Bill_56]

That sounds like normal behaviour for a particulate filter (DPF).

After a while, a DPF becomes clogged and needs to regenerate. The car tries to regenerate by injecting additional fuel, thus the MPG plummets. For many drivers, regeneration completes in a single journey of a few tens of miles, after which the MPG returns to normal. If you are using the car for a fast commute every day then the reduced MPG every so often, lasting maybe 20-30 miles, would probably go unnoticed.

Unfortunately however the regeneration is unlikely to succeed in local driving or short journeys. But the engine management software can't possibly know whether you plan on a long journey so if the filter is clogged, as soon as it gets hot, it starts trying to regenerate. Regeneration fails because you didn't drive long enough, so it tries again on the next journey, and the next, and so on, all the while with reduced MPG.

Taking it for a sustained fast drive finally allows the regeneration to succeed so the car stops the fuel enrichment, and hence your MPG improves. Unfortunately the filter will soon clog up again, that's quite normal, maybe in just a couple of hundred miles. Then you are indeed back to square one.

[Beemer2]

Originally Posted by jp11

What expensive shell oil do you have?

Shell FS1 (Shell Full 100ML) qty 65 £77.35

I don't understand the above as Googling Shell FS1 does not bring anything up.

Maybe someone has an explanation and why 100ML is mentioned x 65?

Beemer

[Beemer2]

Bill,

Today average MPG down to 22.

After full warm up I took it for its 3000rpm 20min journey again today. Average MPG is back to 29. This vehicle gave me 27-29mpg about town for two years. Only now is it giving low mpg and as I have reported twice is has been returned to 29mpg but this appears to be lasting only as you say a couple of hundred miles.

The manual only mentions a 20 min fast run. What else can I do? Surely I should not need to replace the particle filter?

Beemer

[jp11]

Never heard of Shell FS1. Shell 65 is an aero engine lubricant straight SAE30 and wouldn't be good for your D5 at cold start-up. Would also cause high frictional drag and very bad mpg until hot.

[Bill_56]

Originally Posted by Beemer2

Bill,

Today average MPG down to 22.

After full warm up I took it for its 3000rpm 20min journey again today. Average MPG is back to 29. This vehicle gave me 27-29mpg about town for two years. Only now is it giving low mpg and as I have reported twice is has been returned to 29mpg but this appears to be lasting only as you say a couple of hundred miles.

The manual only mentions a 20 min fast run. What else can I do? Surely I should not need to replace the particle filter?

Beemer

It's often quoted that the filter should last the 'life of the vehicle', but I think that refers to the life of an 'average' vehicle rather than a car like a Volvo that may be expected to go many hundred of thousand miles. Still, my understanding is that in normal usage the DPF should last well into the second hundred thousand, maybe much more.

It does sound as if your car was previously coping with the DPF overheads, but perhaps not coping so well now, which begs the question... what has changed?

Within the past 12 months, engine management software updates have been rolled out that, I'm led to believe, were meant to improve the DPF's adaptation to biodiesel blends (as is universally sold at the pumps nowadays). That is certainly an interesting co-incidence and I guess it's possible that the new regeneration algorithms are less suitable for your usage pattern, but it would be very difficult to prove if that was the cause, owing to ALL (not just Volvo) manufacturers' secrecy surrounding their software.

It's also possible that your engine is producing more soot than it did before, hence clogging up the filter sooner. Has anything else changed, or any other signs of anything amiss? Are you using a different brand of fuel, for example?

If the engine is showing any signs of wear, could it be burning a little oil? I honestly don't know whether oil-burning would clog up the DPF more quickly, but I guess it might. How does your oil level behave itself? Does it stay level, or does it rise over time, or does it fall? A gradual rise in oil level is not unusual in a DPF car as the oil gets mixed with fuel during DPF regeneration, but these engines have a good reputation for being oil-tight, so I'd be worried if the level were falling.

I doubt if I'll be able to contribute much more here, but hopefully I've thrown some ideas into the melting pot.

- Bill

[Beemer2]

Anyone know what a garage does to fully clean a diesel particle filter?

regards,

Beemer

[grainqey]

get a big hammer and hit all the gubbins out :P SORTED then you just map the "fuel waster" out lol
...sorry, people are always complaining about dpfs and lower mpgs, just get rid of it and cover everybody in a soot cloud by occasionally cleaning it out from traffic lights lol

[John_C]

A Volvo dealer (probably an increasing number of indies too these days) can put the DPF through a forced regeneration when it gets clogged, as long as it's not completely FUBAR'd. Are you getting any DPF warning lights?

The engine oil is important, I'd ask the garage exactly what they put in. As has already been said the only link I can find for Shell FS1 is that it is a mineral oil for aero engines.... I can't imagine any garage would be so stupid as to use that in a modern diesel engine but you do need to check what they did use is to the right spec.