UKC

Anyone know how critical the engine oil specification is for topping up a diesel engine (Fiat Ducato). 

The oil warning light cam on whilst travelling so I had to add 1/2 l (out 6l total) of oil to bring it back in level range. They didn't have the exact spec that's listed in the manual, so I added the closest thing. 

Both oils are fully synthetic, and of the same viscosity range (0W30). The Fiat recommend one is Selenia WR Forard 0W30. I added Castrol Edge 0W30, and if I look at the Castrol website the recommended oil for my van is Castrol Magnatec 0W30. Should I have any concerns???

It is due for an oil change in 6000km. Is it fine to leave it until it's scheduled oil service??

It's still under warranty, so I want to be sure not to do anything to invalidate it.   

Your engine will be fine.

As a Fiat Ducato owner myself who only uses the very expensive recommended oil I wouldn’t worry about topping up with a different oil.

I would be more concerned with my van needing topping up in the first place. How long since the last oil change?

Thanks for the confirmation.

Its done 24,000km from new. I've done 15,000km since ive had it and I think the oil level indicator was about half when I got it, and it's now back to half after adding half a litre. 

I was a bit surprised, as I never had to top my VW up between services, but I had read elsewhere that it was ok to consume a small amount of oil. 

I would also say it's fine.

It used to be that all you had to consider was the oil viscosity, but these days there's a lot more to consider.

People tend to over worry about oil viscosity but the truth is your engine can tolerate a fairly wide range.

Since you matched the viscosity you can ignore this bit anyway.

Also, you added half a litre. You probably could have added any old 20W50 mineral oil and it would be fine (the internet will likely disagree with this).

For modern diesels the bigger thing to worry about is the amount of ash it creates. If you use oil meant for an older diesels or petrols, it can create a lot of ash and can stuff up your DPF.

Both oils you mentioned are low Ash (C2 and C3).

I think, the stuff you used is better for the longevity of the engine, but worse for efficiency. But with just half a litre added you won't see any of this.

The manufacturer will specify an oil that's better for fuel economy at the detriment to engine longevity in order to meet an Euro requirement (can be worth knowing).

Doesn’t sound like an excessive amount of oil to use in 15,000km.

I don’t do 15,000km in a year, more like 10,000, and I change my oil every year even though recommended oil changes are every 2 years. So the oil level doesn’t really get much chance to drop.

You’re right not to give the dealer any chance to quibble over any warranty claims. 
It pays to be precious when it’s your own vehicle paid for with your own money.

We were told that it would do no damage to use a higher grade oil, so we buy the correct oil for our newer diesel and use it in both vehicles. It's more expensive, but for how much we use not worth having both types in the garage.

I'm guessing regardless of grade, it's better to have oil than run the engine dry.

Nearly any oil is better than low enough oil pressure to put the light on. 

thanks. I couldn’t really have imagined half a litre of slightly different spec would do any harm. 
 

im not worried about the effect on fuel consumption over the next few thousand km’s only that I didn’t do something strange that could potentially damage the engine or reduce lifespan. 

I’m a bit surprised by this. I can’t imagine engine manufacturers would set the low level trip at a point which could cause excessive wear or damage. 
 

it would surely be set at a point before this would occur. 

In fairness, I expect modern cars are set like you say. Older ones definitely are not.

Unfortunately it can. There are different types of oil and they can sometimes have adverse chemical reactions as I found out the hard way. 

I use a 200 grade gear oil in Blower gearboxes. I drained out 10 lts of the manufacturers old oil and put in 10 lts of fresh out of my van stock of a different brand. There is always bits of old oil left in the system but not much. The blower failed after a few days of running and when I removed it and stripped it down the oil had set like jelly.

Cost me £20k for a new blower for my customer and if we have to change oil brands now we drain it, re fill it, run it for a hour, drain it and re fill it again and havnt had a problem since.