Black oil in a petrol-engine

[Lukas]

Hi friends!

 

I would like to ask you a question.

 

I bought my 2007 Mazda 6 with ~ 130.000km on the clock. Full dealer-service-history, serviced every year. When I bought it, they made a new service, the oil was transparent and yellow-ish, like honey. Perfect. After 2000km, I checked it and it was dark.  I had it changed again, of course with a new oil filter too.

 

After some 1000km, it is black again. What worries me now is: It is not a diesel, it is the 2.0 petrol-engined one. And I am driving it almost only on the Autobahn, so longer journeys (> 1 hour). I don´t do short distance drives around town in it.

 

With my other petrol-cars, the oil stayed clear and like honey the whole time between two oil-changes. Why is the oil in my Mazda getting dark so fast?

 

It´s ready for an oil-change again (~ 10.000km driven, oil is black), so should I just have it changed or is there a way to prevent it getting dark so fast?

 

Lukas

[Spiny Norman]

My experience is that's what happens nowadays, oil doesn't stay clear for long. Whether it's modern oil or modern fuel I don't know, but it wouldn't alarm me.

 

[Lacy]

It's almost impossible to get all of the oil out of an engine at oil change time so the little bit of old oil will mix with the new and make it go dark very quickly. Back in the day I used to always use a light flushing oil before putting the new oil in and that was a good way to get most of the old cack out. You can get flushing additives these days that you just add to the old oil before draining but I'm not convinced it does as good a job.

[mrbenn]

Is it possible the garage that changed the oil are sucking the oil out of the dipstick hole rather than removing the sump plug?

 

Seems a lot of places do this now using vacuum pumps. This method will leave some old oil in the sump along with the crap at the bottom (I imagine) and this will darken the new oil quickly.

 

[Vince70]

One of my old cars does the same thing (the other doesn't ).

 

I put it down to the first couple of years of its life being used a company car on long service intervals then when it ended up being used as a private motor it had hardly any oil changes as it didn't do any mileage so never got its yearly oil change.

 

I took the rocker cover off mine when I first bought it to have a look and there was quite a lot of dried old oily crud under there, but I do regular oil changes on the old girl and gradually after a couple of years the oil is now staying cleaner longer.

 

I wouldn't worry yourself over it too much, just change the oil every 6 months or about every 5000 miles and it should clear up over time.

 

Also good quality modern oils contain cleaning agents so will end up quite dirty as the oil is doing its job correctly and clearing out all the built up crud.

 

So just give it regular oil changes.

[Lukas]

Thanks a lot!

[D-Dubya]

just checked the oil in my 2008 Fiat T-jet engine thats been in about 8 months. its dark brown

[willswitchengage]

Again, be happy that all that crap is held in the oil as opposed to gumming up your moving surfaces. The oil window on my bike is clouded up after about 1000 miles, it's nothing to worry about.

[Bobthebeard]

Again, be happy that all that crap is held in the oil as opposed to gumming up your moving surfaces. The oil window on my bike is clouded up after about 1000 miles, it's nothing to worry about.

^^ +1

Some engines are 'dirtier' than others. The oil is just doing what it is meant to do in respect of collecting the muck.