I use the green stuff. However, I have been told by a machinist friend whose business is in rebuilding diesels that the anti freeze marketed for diesels is best. With highly stressed diesels there is a cavitation phenomenon of bubbles forming and bursting on the cylinder liners when using the green antifreeze. This does not happen with the antifreeze made for diesels. The problem is these bubbles erode the liners and eventually will cause a very hard to diagnose and expensive to fix leak.

I have not taken his advice because the green stuff seems to work fine. I changed it again this year when I put in a new hot water heater and after 4 years of use it looked like new. I also don't believe boat diesels actually work all that hard compared to heavy equipment, farm machinery and trucks. It's also one of those "if it ain't broke don't fix it things". Like changing from conventional oil to synthetic.

For all I know I have bubbles merrily bursting away on my liners. My wife is happy about this possibility, she saw a Beta Marine engine at the boat show this year and thinks one would look and work good in our engine room. Very lucky man to have a wife like that.

Wow Bud...how did you get so lucky :)

I don't know what was originally used. Red/Orange is usually and indication of long-life antifreeze and most likely EG. Unless you know the type of antifreeze, my recommendation would be to flush and refill with your new choice.

All diesels use EG. If it had pink it was likely a Dex-Cool EG variant.. Ideally a "fleet" diesel rated EGAF should be used, like Rotella ELC, but don't mix types of EG unless it says "universal".. Even then a full drain & fill would be best.....