What are the major consquences of not flushing an oil system of a large machine if it needs to be flushed? what is the worse that can happen?

This is hypothetical, I'm not actually in this situation.

Here's what can happen (not necessarily in order of magnitude or consequence)

1) Residual wear debris, sludge, varnish, and varnish precursors can challenge the new oil additive package and likely shorten the useful life of the product to be less than if the flush was performed and you started "clean".

2) The solvency of the new product could stir-up sludge, varnish, and embedded debris after the fill. Assuming you have a filtration system installed, you might see initial filter plugging.

3) If you are adding oil that is different in basestock than the original, you might see a crud burst, as well.

Some of the bad things that can happen are based on the existing condition of your system. If it is clean and dry, the consequences are low. If it is dirty, be careful.

As always, there are many variables that have to be considered when making these decisions (capital cost of replacement, planned and unplanned downtime, personnel safety, warranty and regulatory requirements, OEM recommendations).

Good luck

If you are going between 2 base types of lubricants you can have problems as well. Worst case example, going from a PAG to a mineral oil, you will likely end up with something resembling tar if a complete flush is not performed.

For specific answers call Frank the owner or Auto-RX. If he can't answer your question, it's only one more step to his chemist. I beleive that you can get specific answers. They have a lot of experience with autos, heavy equipment and stationary machines.

I've seen their product work on heavy offroad dump trucks that has oil in the pan that looked like tar. After the treatments the inside of the engines looked like they were just assembled, absolutely clean, not even any traces of crud.

There was no 'chunking' and filters were never plugged. They now use the stuff periodically to prevent the stuff from getting started.

http://www.auto-rx.com/