I changed the oil and oil filter in my Ford Focus MK3 2013 1.6 TDCi on the weekend. I reset the service light a few times, but the oil light stayed on. When you rev the engine, the light disappears and when idle it comes back on. I immediately thought low oil pressure.

I took it to a friend of mine and he said change the filter out because sometimes they can be defective. I just don't understand how an oil filter can be defective?

There's no specific way to install the oil filter is there? I know there's a plastic locator bit at the end of it, but that just pushes into the oil filter cap and then twists into the housing, right?

Has anyone ever seen this before?

Low (red) oil pressure warning means exactly that. If it's staying on then you need to find out why. If it didn't do it before you changed the filter then suspect that, if it did then I wouldn't be starting it until you've found the issue

42 minutes ago, DaveT70 said:

Low (red) oil pressure warning means exactly that. If it's staying on then you need to find out why. If it didn't do it before you changed the filter then suspect that, if it did then I wouldn't be starting it until you've found the issue

Yeah it only came on after the service, so it could just be the filter. I'm going to swap it out tomorrow and see if the light disappears. I've just never seen this before.

On bottom of filter is a bit sticking out with o ring on.  This has to push into a specific hole in bottom of housing.  I have always found this tricky as you can’t see the hole when trying to get filter located properly. I don’t know where the hole goes or the point of it. I don’t know if your problem is a symptom of locating it wrongly. 

2 hours ago, isetta said:

On bottom of filter is a bit sticking out with o ring on.  This has to push into a specific hole in bottom of housing.  I have always found this tricky as you can’t see the hole when trying to get filter located properly. I don’t know where the hole goes or the point of it. I don’t know if your problem is a symptom of locating it wrongly. 

I was actually thinking that. I was wondering if it had to locate somewhere but I didn't really check when installing. I'll make sure the new one gets located properly and report back. Thanks 🙏

The issue is fixed! I didn't realise, but the little bit that sticks out of the filter needs to be inserted into a hole in the oil filter housing. A trick is to put the filter in first, line up the hole and then fit the cap on top after. Lesson learned but I guess that was causing low oil pressure.

Glad you're sorted