Why is my car burning more oil than usual?

[BradC]

Hi all, I have a 2008 118i, I purchased this in July 2018, with 69,000 miles on the clock, ever since I have had the car it has consumed oil, on average I would top it up with a litre of oil every 1500 miles, sometimes between 1000-1500 miles, on one and only one occasion it managed to do 2500 miles before asking for more oil, but twice now it has asked for oil just under 800 miles. The car is nearly on 87,000 miles and am worried it will carry on getting worse. I have had the PCV valve replaced as I've read that can be a possible cause but this has had no effect. Is there any way to determine the cause of this, I imagine the cost to repair could be quite high.

The car is not without its other problems, the catalytic converter is in need of replacing and finding out what has caused it to fail in the first place remains the challenge, I think its probably why the last owner had got rid of the car as the mechanic I've got looking at it can see someone has played about with it, the cat that is on there now is actually older than the car itself which means its had cat trouble before, the car does occasionally misfire. Sometimes it will cut out completely when driving it for the first few miles of a journey, only to start right back up again and drive with no trouble. The spark plugs were changed a year ago and didn't look to good so were recently changed, even though they were only a year old. Am told the fuel pump could be a cause of some of my issues, such as the car cutting out, it could be why the car is lacking power which it has been like for quite a while, the cat could be part of that problem too though.

I have had the car running with a diagnostic machine connected, as soon as the throttle is touched it throws up a fuel pump plausibility fault code, is there any hope with this car being fixed?

[Greydog]

Morning Brad

Welcome to the Forum

You say "it asks for oil" how are you checking the oil? or are you relying on the OBC display. At the volumes of oil your getting through I would expect to be able to (a) see evidence of it being burnt, smoke, smell etc. Over filling can cause more issues than is realised.  If oil is finding it's way into the exhaust it will clog the Catalytic Converter so that could well be the cause of it failing. You say spark plugs don't look good ? Sooty, wet with fuel or oil? You have a fuel pump issue confirmed by diagnostics certainly that won't help like wise has anyone checked the fuel filter? Often a forgotten service item.

If compression is good and cylinders hold compression then it is a case of finding what is causing crank case pressure to push oil into the exhaust killing the catalyser. 

Just my thoughts based on the information posted

Dave

[BradC]

Hi, thanks for your comments.

I am relying on the display to tell me when it needs oil, only when it does that I fill it up with a litre of oil. 

As with the smoke I haven't noticed that but when I first took it in to be looked at they could smell it was burning oil.

One other thing I forgot to put in my last post was when the car has cut out on me I can hear popping and banging coming from the exhaust, have been told it is unburnt fuel getting into the exhaust and exploding and could be that that's causing the cat to fail, aswell as the car burning oil, which is why I have had the fuel system checked, the fuel pump plausibility code is the only code that always returns. I was going to have the fuel filter checked but it turns out this car doesn't have one.

With the spark plugs they were a bit oily but didn't look excessive, as far as I can remember the tips of them looked very worn.

The mechanic that has been looking at my car said there is a small vacuum leak somewhere but didn't think it's the cause of the oil consumption, but perhaps it's got worse, the car goes in again next week so I'll ask him to check. I just wanted to ask around to get as much help and information as possible. I appreciate people taking the time to offer me advice.

[Upt'North]

It could be a blocked breather, worn rings/bores, valve guides etc. 

The plugs should be oil free if not then it's certainly being burnt.

When filling do it by the dipstick, if you're overfilling it will only exacerbate the situation. The Cat is probably being killed by the oil. 

The engine could be a victim of BMW extended service periods or of course the mileage may not be accurate. 

Good luck. 

Upt'North. 

 

[Greydog]

The drawing below shows the Fuel Pump and Filter and Regulator for your car 2008 118i so who ever told you you don't have one is mistaken.

The oil level sensors that trigger the OBC are not accurate as Upt'North has said use the dip stick always, putting in a litre at a time could be damaging the engine

 

 

[BradC]

Perhaps the previous owner hasn't serviced the car properly so this may not have helped. My car though doesn't have a dipstick so the computer system is the only thing I have to rely on.

As with the other things mentioned above I'll look into those, I'll update this post when I have made progress with it.

Thanks again for all the help.

[Upt'North]

Wot no dipstick. Now call me stupid....... Thank you....... But is that just stupid. 

I presume it tells you how much oil to put in. 

Upt'North. 

[BradC]

I agree that it's a stupid idea from BMW not to include a dipstick, the earlier models had them, I think it was from 07 onwards that they stopped including them.

But when it does want oil it does ask for one litre to be added. 

[meltedFootball]

i had very similar issues and had almost every part they could think of replaced some 3x .... . . 

 

so about a month ago, i randomly decided to switch from using only Chevron gas to 76 gas instead. 

 

within one or two tanks the choking, misfiring to limp mode all but disappeared. 

 

i hope this helps with at least the misfire.