Anybody ever run this stuff? It's a HOAT fluid that's ethylene glycol based just like the common yellow stuff, but has added silicates for aluminum protection (G11) I just don't want any problems down the road.

Never heard of it... where do you buy it?

My personal feeling is you should change the coolant every 2 yrs
some of the old cars that have the fill cold line and leave air space dont like coolants like the dextron 5 year stuff ...air in the system has caused a white milky foam when you pull off the cap ... you would need to run a closed system with a recurlation tank like the new cars to keep a full system with such coolants .

Auto coolants used to be simple. Every two years you flushed your out your old coolant and replaced it with new you got from your auto supply store.
Recently (1994-96 for GM, 1997-98 for VW, 2002-03 for Ford, 2001 for Chrysler, ...) manufacturers started using extend life coolants with different anti-corrosives for longer life (because people neglected to change it every two years). Some were hybrids with combinations of the new organic acid technology (OAT) and old ingredients like phosphates. The europeans (VW, BMW) didn't like phosphates because of the reaction of their hard water with phosphates; The Japanese (Honda, Toyota) on the other hand liked phosphates because they worked better than borates. So manufacturers started selling proprietary formulas in a variety of colors other than the traditional green and specifying that you use their brand, which was, of course, more expensive.
Many of the owner's manuals will say something like Subaru's:

"The SUBARU Genuine Coolant containing antifreeze and anti-rust agents is especially made for SUBARU engine, which has an aluminum crankcase. Always use SUBARU Genuine Coolant, since other coolant may cause corrosion."
Most experts agree you don't have to use the manufacturers coolant. The new extended life coolants from Zerex, Prestone, ... will be just as good.

The new antifreezes or Extended Life Antifreeze Coolant (XLC or ELC) use Organic Acid Technology (OAT) containing neutralized organic acids (organic acid salts) that protect engine parts from corrosion instead of the inorganic inhibitors such as silicates, phosphates and / or borates in the old (green and yellow) antifreezes.

OAT is recommended in engines with aluminum components (heads or radiators) such as Subarus and VWs because Borates can be bad for them. OAT coolants also have extended lives, up to 150,000 mi.

Hybrid OAT (HOAT) coolants, such as "Zerex G-05¨." Use organic acids, but not 2-EHA (2-ethylhexanoic acid) (different organic acids are used). Hybrid OAT coolants add some silicate to provide quick-acting protection for aluminum surfaces.

Several web sites said you should avoid mixing traditional coolants (blue, yellow or green) with Organic Acid Technology (OAT) (orange, red, pink) or HOAT (yellow) coolants. The OAT will cause precipitation of silicates in the green type and corrosion protection is greatly reduced.
However, many of the aftermarket coolants (e.g. Prestone, Zerex, Peak) now have a universal coolant they claim is OK to mix with anything.

According to Car Talk SAE (the Society of Automotive Engineers) said that you can mix up to about 15 percent traditional coolant in your OAT coolant before you have any real effect on the corrosion inhibitors.

Read more at
http://www.geocities.com/dtmcbride/home_garden/auto/antifreeze.html

Yikes!! Great info, but also confusing. HOAT still sounds compatible with the old Prestone yellow stuff if you don't quite get all of it flushed.