[SirKeats]

here's what the RP guy said (i'll omit his personal info):

first my email to them:

I have been shopping around for an alternative to the GM Synchromesh transmission fluid for my 1989 Geo Metro and was pleased when I found Synchromax at my local auto parts store. However, despite the claims on the Royal Purple website that the Synchromax product is appropriate for vehicles requireing the GM Synchromesh fluid (PN12345349), I've just been told that the GM fluid (as well as the Pennzoil alternative) has a cSt @ 100°C of 9.0-9.5 while the RP Synchromax is only 7.7. I was further told that this could result in damage to my transmission.

This is a major concern as I've already put your Synchromax oil in my 5spd manual transmission. I'm worried now that I could be causing my vehicle harm.

Can you please explain?

Thanks,

Nick

their response

Nick,

Thanks for the email and for choosing to use Synchromax in your Metro.

First. How is it working? Excellent right. Improved easier shifting - less niose, lower temps.

Your concerns are not well founded and are probably being fueled by those on the internet that like to think of themselves as lube experts but hold day jobs in another field of work! I do this for a living and have traveled the world improving lubrication.

Although marginally lighter in fluid thickness, or viscosity at 100 C, the Synchromax has 300 percent greater oil film strength which prevents metal to metal from happening due to our advanced additive technology. By stopping friction and metal contact better, operating temps drop and the slight viscosity difference becomes negligible in the bearings.

I'm using the same Synchromax in my personal vehicle which is putting 650 lb-ft of torque through the manual transmission.

RP stands behind the recommendation to use the Synchromax in your 89 Metro manual transaxle as the fully synthetic base oils and additives offers superior wear and high and low temp performance above that of the mineral based OEM fluid.

Email me direct if you have additional ?

Thanks,

David
Tech. Services
[omitted]
Sent from my Verizon Wireless BlackBerry

not trying to argue here... just wanted to share his opinion on the subject. i may end up switching out anyway. i don't wanna risk damaging my tranny.