Dipstick

[FIBAMAN]

Originally Posted by Tatsfield

Warning to those who might not know but the older D5 diesels had DPF regeneration problems which resulted in unburnt diesel fuel being dumped into the engine oil sump. If the sump was filled to "Max", the additional fluid would dilute the oil and raise the level to above the safe maximum level which could result in over-pressuring the engine. The Volvo solution to this problem was to calibrate the electronic oil level display to show 75% of the maximum capacity as full and leave the 25% available to take up dumped diesel. However they did not change the dip stick but merely made a technical notification that the oil should not be filled above 75% of the empty to max range. Anyone not knowing this and seeing that their dip stick showed the sump as only 75% full might take the advice innocently offered and end up overfilling their sump. It has happened!

It's all down to an originally poor DPF design and a ham fisted Volvo solution. Later changes to the ECU programming minimised the problem but some poor owner could cause himself trouble if he blindly filled the sump to the Max!

WTF
A cockeyed solution if ever there was one.
With 25% fuel dilution would probably wreck the engine anyway

[tt82]

The difference between min and max on the dipstick is 1 litre so that 25% of the 1 litre is actually only 4% of the total 5.7 litre volume of oil.

[FIBAMAN]

Originally Posted by tt82

The difference between min and max on the dipstick is 1 litre so that 25% of the 1 litre is actually only 4% of the total 5.7 litre volume of oil.

TT, I appreciate your input but in my opinion (and experience, that would still be a damaging concentration.
I would like to know how the fuel gets in to the sump in the first place.
The whole scenario just doesnt make sense.

[tt82]

AFAIK, the injectors inject diesel on the exhaust stroke so it is taken into the DPF where it is burnt to raise the temperature to the 600 degrees C need to burn off the soot. It's when doing this that small quantities of diesel can seep past the piston rings into the sump. It's more common with diesel engines that are used for short journey and aggressive regeneration takes place. For those that do high mileage journeys, this isn't a problem. I've done over 100k miles in my D5 in 5 years and never had an issue with the oil level rising.