Oil still black after change and vacuum oil extractors

[Jan]

"If the engine oil is changed at regular (recommended) intervals" is the usual reason given for not flushing engine. If the car is second hand and the current contents of the sump are completely black how do you know what the actual service intervals were from the previous owner(s)? The obvious answer is that you don't!

Some owners barely know how to open the bonnet to check the level/quality of any of the replaceable fluids and will blithely soldier on for years with nothing more than topping up the windscreen washer fluid, but only after it runs out. Others take the car into a garage which uses the vacuum suction tool to 'drain' the sump through the dipstick hole (often with a cold engine) for speed, which leaves a lot of cr4p in the bottom of the sump.

On many cars it's quite easy to drop the sump to check for an accumulation of 'clag' in the bottom, but on many cars it's a complete PITA to remove and refit it. If you're dead set on not using 'unknown chemicals' in the engine then just refill with any cheap oil, leave it in for a couple of days and simply drain it off while the engine is still hot from a decent run (discarding it according to local laws) and refill with fresh oil of the correct grade. What's 'snake oil' about that?

 

[Rig Pig]

Nothing wrong with that at all, the 'snake oil' is in the engine flush!

 

[DAPPH]

Come on: Cast in situ and machined white metal bearings haven't been used since before WWII! Modern shell bearings are much tougher than that.

On a newly acquired used car I always flush it through at least once, if not twice, to get out all the crap before refilling it with fresh oil and putting on a new filter. My latest acquisition - a British built (Rootes) Dodge 50 motor home - had oil in it that was a black as a lump of anthracite in a cellar at midnight with the lights off. Before the flush there was excessive blow by and a significant jet of fumes from the sump breather pipe. After the flush the oil has stayed nice and clean and the blow by has reduced to almost nothing. The previous car (since stolen) was in even worse condition as the person I bought it off had done nothing but put DERV in it during the 5 years he owned it! A double flush later and the oil stayed clean right up to the next oil change and even running on a mix of filtered veg/used sump oil/unleaded it passed the emissions part of the MOT with flying colours. In most cases it's just a matter of making the flushing oil from a 5:2 mix of cheap oil/DERV, only using half the full sump quantity and then only letting the car idle for 2-3 minutes so that it gets into all the little oilways. With 7 litres you have enough to do it twice the first time or just the once and again at the next oil change Despite the number of cars I've done this on over the decades I've never experienced any problems with it.

Psssst !
We made cast white metal bearings in 1966 as part of my engineering apprenticeship .

They were used on loads of military railway gear & several old 1950's cast iron piston engines as well as various slow turning shafts . We used to use massive jig held reamers along with scrapers & engineering blue to get the correct fits on axles, journals and cranks .

 

[doubleboost]

The problem with "flushing" a very dirty engine
The hard carbon like deposits simply block up the oil strainer
Starving the engine of oil and damaging the engine
The ford CVH engines were favourite for it
You could remove the rocker box and scrape out the hard carbon / sludge deposit
Modern engines with long life, low ash oils are no problem
I recently changed a sump on a VW golf PD Diesel with 170,000 miles on the clock
It had a oil & filter change every 20,000 (proper speck oil)
The engine was still clean inside
(the sump had a jack hole in it) lol