Engine oil flush

I've never used a flush before but I have used running in oil in the engine idling for 20 minutes before draining that and replacing it with normal grade oil and a new filter.

My advice is never use engine flushes - much better to do a series of oil changes as short intervals say 1000 miles at a time using a cheap oil

If you do use an engine flush follow the instructions with it to the letter - It is not the case that if 15 mins at idle is good leaving it in for a week and 500 miles is better

I've read a lot to say engine flush in an old engine is a bad idea - loosens a lot of curse word you'd rather it didn't.

Lots of professionals say, as already suggested, more frequent oil changes with a cheap oil.

You always gets bits of crud, metal particles, worn off bits, sat here and there - in dead end galleries, plugged drillings in cranks etc.

Undisturbed, it's fine - no harm being done.

Loosen it, in an engine you have no idea of the prior history, and it may well cause issues. Not to say it will - but it might.

I have an unopened can of flushing oil I bought 30 yrs ago but was told by garage owner I respected not to bother, due to the potential to do more harm than good.

If the engine is being serviced in the normal way, with regular oil changes with decent oil suitable for the engine and the use it's being put to, you have no need for flushing oil - that's my opinion with 30 yrs of engineering design and maintenance experience since.

I've used engine oil flushes in the past and not noticed a huge amount of difference but I could have been starting with a fairly well maintained engine..

I often hear the notion of issues with flushes dislodging stuff inside the engine, but I don't know how many engines have actually failed that way or if it's one of those things that gets often repeated around the internet?

Engine oil in itself often ends up being quite a contentious topic!

The one that I have experience of didn't fail as such (an early 24V Senator I got cheap - right place right time) I looked inside the oil filler cap and it was black and full of carbon - I'd never seen an engine as bad, it looked like it had never seen an oil change, I was much younger and to me it seemed like an engine flush was the solution however it went from

1. a quiet engine to a very rattly one all the hydraulic tappets started complaining very vocally

2. a 500ml of oil per 3,000 mls engine (admittedly poor for one of these engines but it didn't visibly smoke and didn't leak oil) to a 1 litre of oil per 500 miles which was quite frankly embarrassing to drive (due to the smoke kicked out on acceleration and deceleration)

Engine seals (crankshaft seals) that were previously dry leaked profusely

I've got some pictures somewhere of the head when I stripped it down and compared to a normal well serviced cars it was basically tar and carbon coating over every part that didn't move.....

I've never used a flushing solution since - I've had other cars with patchy service history and adopted a several oil changes in short succession and never had the same issues (to me it just seems a much more gentle way to try to remove deposits slowly and clean up the internals)