I was under the imression that all the Dexcool stuff is orange just so you know that it's the dexcool with the oxyacids in it. Might be wrong though but I know the only prestone dexcool I've seen is the silver bottle and the actual coolant is definitely orange.

If you look at www.zerex.com (forwards to a page on valvoline but you get the idea). It has pretty detailed info on all their coolants. The G-05 is absolutely phosphate free and just a standard ethlyene glycol base without the oxyacids. I wish it didn't have silicates but I think the phosphates are a bigger problem on an aluminum engine. It does claim to be low silicate content but I have no clue what high silicate content would be. I would think Prestone will probably be coming out with a G-05 equivalent soon too since it's coming standard on Ford and Chrysler stuff now.

For what it's worth the guy at the Porsche dealer said you shouldn't get the orange stuff within a mile of a P-car. Granted it's an opinionated subject so don't take it too seriously. He was just a parts guy that used to have a 944 Turbo not an old timer mechanic. One of the bigger independent Porsche shops here in the Phoenix area just uses plain old green stuff and doesn't have any issues with it, I pulled green stuff out and haven't noticed any pitting inside the head where I've looked in it, so I think we all probably worry about this subject way too much anyway. That said, phosphate free definitely isn't a bad thing.

 

methinks as long as you have plenty of grounds you won't have a problem with electrolysis pitting.

i could be wrong...

-Mike-

 

My apologies, it comes in a green bottle I believe.

I dont remember the color of the fluid itself, orange/red seems familiar though.

 

When I got mine from Audi/vw there were two to choose from and neither said phosphate or silicate free. Called number on back which turned out to be valvoline IIRC. They told me one is phosphate and silicate free and the other isn't.

 

I'm pretty sure my 944 came with green antifreeze. I'll bet it wasn't phosphate-free. That was 20 years ago and I didn't hear anything about phosphate-free until about 10 years ago. I'm sure it's a good idea,and I have the orange stuff now, but maybe it doesn't make much difference. Has anyone personally seen an engine that was properly maintained that was damaged by the green stuff?

 

The Zerex G-05 is sota (state of the art) in anti freeze. Very aluminum friendly. And according to the MBZ crowd it is less stressfull on plastic radiator tanks.

Lynn Poole
'86 951,' 82 300CD MBZ

 

shhh.. i know the door man..

 

So what exactly do the phosphates and silicates do to the engine?

 

Phosphates cause the minerals in the water to plate out in the engine, blocking up coolant passages, gumming up water pumps, oil coolers, etc.

I have seen pictures of oil coolers from cars that didn't run phosphate free antifreeze, and it's really obvious when you see one.
I pulled mine out, it looked like it did the day it went in.

Silicates are harmless (supposedly) to our engines, it's just nice to know that an antifreeze is silicate free.
What I mean is, there are no warnings about not using silicate free antifreeze in our engines.

I checked my bottle of prestone, and all it says it's GM DEXCOOL approved, and is compatible with all DEXCOOL approved coolants.
Been running it for a few months now, with no issues what-so-ever, although I (at present) have a small coolant leak, I think it's the rad drain plug.