It's been bugging me for a while. Shops sell two types of 5W40 engine oil, one for diesels and the other for petrols. Is there any difference between them?
Probably. bear in mind that there are individual manufacturers specs for oil, ford, vw, vauxhall etc are all a bit different.
Also depends on the age of the engine, some are fussier than others.
I believe derv oil has a stronger detergent within the oil. Probably a fair few other additions but unsure
More detergent in diesel oil, I used to run my v8 rover on it and it stayed lovely and clean inside instead of the usual sludged up mess you find.
quote:
Originally posted by mark chandler
More detergent in diesel oil, I used to run my v8 rover on it and it stayed lovely and clean inside instead of the usual sludged up mess you find.
Back in the days of mineral oils there used to be big difference in the amount of detergent and anti-varnish additives although many mineral oils sold
for petrol engines contained sufficient additives to meet the minimum demands of specifications for diesel engines. Less difference these days as
synthetic oils are more resistant to breakdown at higher temperatures which causes sludge and varnish.
If you want an engine that is clean internally run it on synthetic oil.
Incidentally synthetic engine oils were developed by the Nazis during WW2 to resist the extremes of temperatures lube oil is exposed to in jet
engines.
[Edited on 5/6/15 by britishtrident]
quote:
Originally posted by britishtrident
Incidentally synthetic engine oils were developed by the Nazis during WW2 to resist the extremes of temperatures lube oil is exposed to in jet engines.
[Edited on 5/6/15 by britishtrident]
Back in the day, before synthetics were common, there was a lot more detergent in diesel oils. As the oils (and detergents) improved the the
difference became less and in a lot of cases the oils labeled as petrol or derv specific, were in fact the same stuff. It was just packaged that way
because the buying public expected it (heard same story from both Shell+Valvoline technical guys).
There is a difference now though with the introduction of DPF's as with them you need a low-saps/low-ash oil. Use a none low-saps oil and your
DPF will soon block up.
The specific VAG/BMW?Merc/GM/Ford/etc specific oils might all be for slightly different OEM requirements but again, the oil companies have oils that
meet most/all specs, but find it often sells better (and often at a higher price) if packaged separately.
Right, so there's no difference in the oiliness, for the same grade. But Diesel engine oil is perhaps better for cleanliness. Except for cars with a DPF, you could top up with either and it would make little difference.
All the oil I've bought recently has been for both petrol and diesel. It was fully synthetic Ford spec. though.
quote:
Originally posted by smart51
Right, so there's no difference in the oiliness, for the same grade. But Diesel engine oil is perhaps better for cleanliness. Except for cars with a DPF, you could top up with either and it would make little difference.