When did Castrol GTX formulation change recently?

[fendertweed]

I'm trying to determine if I have the older formulation (OK) or the newer (not OK) in my '73 911 ... tried a search but couldn't pin this down: when did the newest formulation of Castrol GTX 20W50 hit the shelves in stores? Sometime in '07? Earlier?

Thanks for any info you can give,

Jon

 

[dave1251]

What is a problem with a newer formulation of GTX?

 

[MGregoir]

The newer 20W-50 is SM but it is not GF-4 Energy Conserving which is what limited the ZDDP concentration in it. I would not worry if that is the issue.

 

[cheetahdriver]

if this is the problem i am thinking of, it caused GTX to drop off of the GM approved list because of a problem with low temp pumpability. i have no idea when they rectified it, though.

 

[kballowe]

I don't know about your 911, but this oil returns excellent UOAs in my Harleys. Castrol 20w50 has always been decent motor oil. Not the same thing, I know - just sayin'.

 

[dave1251]

Does anyone have any proof SM oils are bad for flat tappets?

 

[Dyoel182]

Originally Posted By: MGregoir
The newer 20W-50 is SM but it is not GF-4 Energy Conserving which is what limited the ZDDP concentration in it. I would not worry if that is the issue.


Why would you expect a 20w50 be energy conserving?

 

[fendertweed]

my long time trusted friend & indep shop owner says he has seen some very bad issues w/ older 911s on new Castrol, wonder why if the ZDDP thing is not an issue... that seems to be the concern, not energy conserving ratings?

He is recommending going over to Penn Grade ... having spent $$$$$ on a rebuild at 60k several yrs. ago I'm not taking any chances.