To Flush or not

[globetrotter]

Hi All, my celebration has just tipped over 170k, and is due for an oil change, should I use engine flush first, or leave well alone?

[jpliddy]

hi there is different views on this subject i was told by millers oils as my 940 diesel has had its oil and filter changed every 5000 miles for the last 18 years with millers XFE semi synthetic to not do a oil flush .
so it would be interesting to see what some of the more knowledgeable engine techs on here say . about this subject

[Forrest]

I have two 940s that are still running very sweetly on 200k and 250k miles without ever having done an oil flush. In my ownership they have never gone more than 1,500 miles beyond the recommended 10,000 mile service interval. Looking through the oil filler cap what I can see still looks very clean.

If yours has been neglected in the past then a flush might help but there is always the risk that it will dislodge deposits from where they aren’t doing any harm enabling them to shift to somewhere where that they will.

[aardvarkash10]

Originally Posted by Forrest

If yours has been neglected in the past then a flush might help but there is always the risk that it will dislodge deposits from where they aren’t doing any harm enabling them to shift to somewhere where that they will.

This.

If you REALLY want to go down the path of "flushing" think about where the practise came from first.

In the last 30 years the quality of engine oil has improved significantly. Even relatively cheap oils now contain additives that are designed to remove carbon and varnish deposits as a matter of course. Prior to this, and back into the 1940's and 50's engine oil was a pretty basic lubricant and not a lot else.

Unless there is a very good diagnosed reason for hitting an engine with a high detergent product, leave alone. Use a reasonable quality engine oil, change regularly, change filter at every oil change and enjoy.

[Laird Scooby]

I'm with the others on this one, don't flush unless the oil changes have been neglected for some time.

However, if you think the engine may well be dirtier inside than it should be, perhaps because of a few overdue oil changes, add some synthetic ATF to the engine oil about 1000 miles before the planned oil change. This will help to gently clean the engine inside and also revive any ageing oil seals.

It also works wonders on hydraulic tappets but you can safely add the ATF and leave it in there between oil changes. When i say "some" about half a litre is about right.

[baggy798]

For the first 4 oil changes I added a bottle of Millers engine flush beforehand. No problems.

Following year I changed oil normally, then added Seafoam and changed it again after only 200 miles. The oil that came out was absolutely black and filthy.

About 2000 miles afterwards and I still could hardly read the oil on the dipstick it was that clean.

No problems. The oil leaks have not got better or worse.