OK, I've just done a change on a 4 litre ED motor that hasn't had the oil or filter changed for 40,000km. Also did the rocker gasket since it was pissing out of there.

Top of the motor was clean, no oil sludge deposits, has about 280,00km on the clock. Oil was a bit thick but not lumpy as it was coming out of the sump.

So, put fresh oil and new filter in, start motor and it starts blowing s**t of blue smoke. Smell it and its certainly oil. Welll, s**t I think.

So the owner isn't impressed that an oil change most likely damaged his engine. Running it for another 5 minutes, most of the smoke stopped coming out of the exhaust. I reckon all the old oil formed a huge sludge all throughout the motor, especially in the piston ring lands and valve stem seals. The fresh oil washed all this crud out and much of it got burned and blown out the exhaust. The motor was certainly a bit noiser mechanically as I reckon much of the damage has been done.

Sound like what happened? Plausible?

sounds about right to me.

Looks like it had very thick oil in it to stop it smoking... prob'ly that horrid stop smoke goo that poeple like to put in smokey motors. Now its got normal oil its back to how it was.

Do a comp test and see if the rings are worn

Like they said the engine was already worn. Oil looses its lubricating properties as it gets older (used0 also it gets diluted. If it was thick thats why it was quieter than when it had fresh oil. If the customer complains to much tell them its their fault for goin so long without changing the oil and filters.

i've had the same thing happen to me befor. it was a 626 wagon changed the oil and it started to smoke really bad.

but there is nothing you can about it

Ahhh is this the ute? .. that burns oil? ... so he don't need to change the oil, cos it burns it, he just tops it up? ... ... hahaha, guess thats why he didn't ever need to do an oil change!!

What oil did you put in it? ... bet the tappets are really noise now ..