Hi Graham. Sometimes I do and sometimes others. Which I guess is potential for a lack of good data which is my fault. For sure it looks very dirty for just a ground run. Thanks. J
Graham wrote:
Or they drained if cold. Either way, a small quantity of dirty oil mixed in with the new.
I agree.
Looks like oil wasn’t fully drained?
That seems to be the evolution of thought. A pint of blood goes a long way on the floor. Maybe it’s the same with the dirt in oil….
Definitely not old oil. I would say under 20hrs.
If you think somebody (who said they changed the oil) didn’t change it, you can’t tell from the photo unless you saw the previous oil. How old was the previous oil? If 50hrs then I’d say they definitely changed it.
In the winter, oil won’t drain properly unless engine warmed up.
FP or CS prop?
CS will mix a higher amount of old oil with the newly added.
Also, oil cooler location, turbocharger lube and control drained, separately at oil change or not, and multiple other factors mean the criteria is very much airframe-specific.
Send a sample of your old oil over to blackstone labs in the US, they’ll tell you if there is anything in there that is not supposed to be there. I find it really helpfull and now even use them for my hobby car. They also observe trends when you use them for a couple of oilchanges (increase in certain deposits that would indicate wear of certain specific components and/or bearings).
@Bobo quite popular in the USA to get oil analysis trends. The thinking in the UK is that this makes sense for turbines but you risk false positives. These old design engines make a variety of carbon and metal, and eyeballing the open filter for metal and carbon should be sufficient. It is quite obvious if your engine is not happy by inspecting the filter carefully.
I’ve just seen the way the thread has displayed the photo. It cuts off the bottom part so here’s the full image which may alter things a bit. 
I’ll send some to the labs and see what they come back with. I’m also going to send them some after an hour of running from fresh plus the next proper change so they have a baseline to compare. I’m going to assume the build up of carbons and deposits is somewhat linear and from this we should be able to get a good idea if it was properly changed. It should be a fairly binary result between one hour and twenty five. Thanks for everyone’s input. J
