Originally Posted by Steve - UK

Just jumping in here with extra bit of info' ref the old engine flush idea. Of course before draining the oil we always suggest running the engine for a few mins to make it thinner and it will drain quicker. Many people also buy an engine flush to rinse out any accumulated gunge. You pour it in (with the sump plug finger tight) let it stand and then drain.
Now here's the interesting bit - My father (now elderly) for many years was a respected racing engine builder and tuner in the 60's 70's early 80's. Some very well known British motor racing teams used his expertise. Now he always flushed after draining the oil saying any sump debris should be removed as it can cause damage due to it being disturbed and then swimming around in our lovely fresh Mobil 1. He used to replace the sump plug and filter, and fill up to maximum with diesel fuel.Then run the engine for 1 whole minute, before draining off and checking in the bottom of the bucket for any metallic debris, and there always is some.

Originally Posted by SparkieSRT6

DIESEL FUEL?????
I wouldn't even try that in my 1975 lawnmower engine.