To flush or not to flush?

[Precise1]

Part of what is being missed here is that when you drain your engine oil not all of it comes out, no matter how long you have the plug removed. There are all sorts of little areas where it collects and stays, and colors the new oil that is added. That doesn't mean the flush didn't clean the inside of the case well, it means you mixed some of the old, suspended gunk with the new oil.

 

When I flushed my motor (with a additive like what you describe) and drained it, I changed the filter, put in cheap oil, drove it normally for a few days, then drained it and changed the oil/filter with quality synthetic. The first oil change still had quite a bit of color and smell to it, the second looked and smelled clean.

 

Also, ATF is really hydraulic fluid, not an oil, even though it does lubricate to some extent. The two systems are totally different, and ATF is not intended to run at engine temperatures.

Now that you have run an engine flush product, I think you would be far better off just changing the oil/filter until you have flushed all the old liquids out and the new oil is clear.

 

B

[Slartibartfast]

^+1, a lot of oil stays in there. I was surprised at how dark a little ATF made my oil the first time, and how quick the new oil seemed to go dark. This time I poured some oil through it before filling. It came out black, then lightened up, and the oil I put in afterwards hasn't darkened as much as the last batch did. I figure there was some black oil pooled at the bottom of the pan. The drain plug isn't at the very bottom of the pan, so you can't get all the oil out unless you chase it out with something.

[Terranovation]

One thing I did notice about the old used oil was when I had the drain pan standing up draining into the oil container. Majority of the oil had already drained into the container and the drain pan had a coating of black oil still clinging to it, even after 2 hours. So I thought to myself that's what the inside of the engine must be like too, even after a whole night draining. There might be no drips coming out, but the stuff is still stuck in there somewhere.

Next time I will definitely try filling up with cheap oil then change that and fill it up again which should get rid of most of the black stuff.

[Alkorahil]

IMHO flushing is not a bad idea if you refill with heap oil and filter, drive it for a day or two then drain and refill with good filer and oil to get everything out.

Whenever I buy a new vehicle that I dont know the history of that well I do this.