Re: [ST] Motul products

[Blake Sobiloff <sobiloff@xxxxxxxxx>]

On Mar 14, 2006, at 5:49 AM, <sprint_st@xxxxxxxxxxx>  
<sprint_st@xxxxxxxxxxx> wrote:
> On coolants, they are usually color coded but I'm not sure if that  
> is an international standard.

Unfortunately, at least here in the US, there is no standard for  
colors anymore and manufacturers are using color as a marketing tool  
instead of a reliable indicator as to the kind of coolant. Buyer beware!

> That usually kills two birds with one stone because the ones that  
> mix with all colors don't have silicates or other aluminum and/or  
> water pump damaging additives.

Silicates are only a problem if you use tap water to dilute your  
coolant (instead of distilled) or if you don't change your coolant  
every couple of years. In either situation they can precipitate out  
of solution and act like sand, damaging your water pump. When the  
silicates remain in solution they provide excellent cooling system  
protection from wear and corrosion.

DexCool, a popular type of coolant from GM that uses organic acid  
technology (OAT), works great until you get some air trapped in the  
system, then it turns into a gelatinous sludge. This is a problem  
with all OAT-based coolants. OAT is great because it protects much  
longer (5-10 years) than silicates (1-2 years), but the OAT takes a  
few months to bond with metal in the system, leaving the system  
vulnerable for a while at first application.

The Japanese coolants, which are (mostly) silicate free, work well  
without drawback except that they're typically expensive and there  
aren't good non-OEM sources. There are also subtle differences  
between the levels of silicates and phosphates in the Honda, Toyota,  
and Nissan flavors.

My new favorite is Zerex's G-05. It is very similar to what Mercedes  
has been using for 20 years with good success. It is low silicate and  
phosphate free, and uses a hybrid organic acid technology (H-OAT).  
The silicates provide immediate cooling system protection until the  
OAT can take over, but they aren't in high enough concentrations to  
cause problems. The coolant also tolerates air in the system, unlike  
DexCool. And, it'll last up to five years and is safe for aluminum.  
(Being slightly O/C I still change it at about half that interval,  
but that's just me and it's better than changing every year like I  
did with traditional coolants.)

> Mixing 5.1 with 3 or 4 is OK in a pinch, but never mix Dot 5 with  
> them.  Did I repeat myself??

Can't emphasize the point enough: DOT "5" is silicone-based and not  
compatible with any other kind of brake fluid, while DOT "5.1" is  
compatible with DOT 3 and DOT 4 and has performance characteristics  
similar to DOT 5. Stay away from DOT 5!

> It's very important that you try to get the highest dry and wet  
> boiling point brake fluid specified for your brakes.

The last time I researched the issue (about a year ago), Motul's  
RBF600 brake fluid had the best dry (594 dF) and wet (421 dF) boiling  
points of any product on the market. I've used it for about five  
years, flushing my brakes yearly, and have had excellent performance  
from it.
--
Blake Sobiloff <sobiloff@xxxxxxxxx>
<http://sobiloff.typepad.com/>
San Jose, CA  (USA)


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