Engine flush, thing of the past?

[21TonyK]

Is it still the done thing to use an engine flush as part of an oil change? Car has a service history and normal oil changes but I doubt anything like that has been done in 90K+ miles.

[Tony1963]

People who intend to keep a car for many years are the only ones who should be considering it. With care and maintenance, and a reasonable approach to oil changes, an engine should last a few hundred thousand miles, no problem. But if you can see yourself wanting to keep a car for say 400,000 miles with the original engine, yeah, why not.

90k miles is nothing now.

[steveo3002]

its still a thing , although when it dislodges some filth will it do more harm than good circulating through the bearings?

unless its an engine known to sludge i would just keep on with regualr oil changes

[Krikkit]

Snake oil, no ta

[TwinKam]

I never do an oil change without a chemical flush, and have been using it professionally for the past 30+ years, so that's literally thousands of oil changes. Never caused a problem, ever. Never been queried by a customer, ever. The benefits (apart from a quicker drain time) are clear to see whenever an engine is opened up, eg cam-cover or sump removal; they still look like new, no gunge, no sludge. That makes them far more pleasant to work on and, I would argue, keeps the oil cleaner for longer; dirt is the enemy, so it's better out than in. All for the sake of a few quid (Wynns, STP etc IRO £6, no added time cost involved).

[GreenV8S]

steveo3002 said:

its still a thing , although when it dislodges some filth will it do more harm than good circulating through the bearings?

If you have contamination between the pump and bearings, I'd say it's only a matter of time until it reaches the bearings. But I expect most contamination and sludge would be downstream of the bearings, where dirt and sludge have settled out of the oil instead of being carried down to the sump. Encouraging it on its way seems like a good idea. The only downside I can see is the need to run the engine with the oil degraded by flushing additives, but I don't see that as a problem.

[steveo3002]

if its always been serviced then probably doesnt need it

if its been abused and full of sludge then the damage is already done ?

if i knew i had some old stinker full of rubbish i would at least clean out the sump ,oil pick up and rocker cover then see how i feel about it

[donkmeister]

The prevailing wisdom when I looked into it was that modern detergent oils are so good at holding on to the crud, that with regular oil changes there will be no sludge to flush out. An alternative you can consider; in MG Rover circles the approach is to drain the good oil, refill with cheapo oil of the correct spec, run it for a week and then drain/refill with new good oil. You do get a bit more out that way as the pint or so of old oil lurking in the engine gets diluted down into the cheapo oil.

My own experience (a sample size of two) of doing jobs on mates' cars that hadn't seen an oil change in at least 30k miles, there was no sludge or gunge under the rocker covers. In both cases I insisted we do the oil too and it was black as anything (carbon, I guess) but not gloopy or lumpy. So even if some rotter has missed an oil change or two, it's unlikely that you'll have the sort of sludge you see on American "Just Rolled In" type videos.