I wrote this to answer the basic questions people have about GC. The forums are intimidating and finding information can be tedious. I hope this helps anyone looking for basic info. If you see any errors or have suggestions, please PM me. GC FAQ Created: April 3, 2006 Last Edited: April 15, 2006 Disclaimer: This FAQ was written for the U.S. audience. Not everything here applies if you live in another country. Basic information:
GC is good enough to have its own forum! That's gotta mean something. Bottom Line
Click here for some photos of US and Green GC.
The Gold GC bottles look similar or identical to the Green GC bottles.
- What is GC? GC stands for German Castrol. It's officially named Castrol Syntec 0w-30. I'm not sure who coined this term.
- Why is it called GC? It is the ONLY Castrol Syntec made in Germany.
- What makes this stuff so good?
With any oil, it may not work well with your car. However, the majority of us love it.
- Produces great UOA results.
- Engines run quieter and smoother. (OK, that may be an opinion.)
- Comparable price with other synthetics. ~$5 qt
- GC is a TRUE synthetic. Made from PAO/Esters, not Group III. Click here for more reading.
- The other Castrol Syntecs are not true synthetics. Other examples of true synthetic oils are Mobil1, Amsoil, Redline, and Royal Purple to name a few!
- What's bad about this stuff?
- You might have a hard time finding it depending on where you live.
- Your car might not like it. You'll never know until you try. Keep trying oils until you find one you're happy with.
- Addicting. You'll see what I mean...
- Is it "thin"? Come on, 0w-30 has to be watery.
NO! Please don't completely buy into that myth.
- At cold temps, the 0w weight correlates to cold cranking viscosity. That means GC will still flow at cold temps. (Which is a good thing!)
- At operating temps, the 30 weight is actually close to a 40 weight. GC is one of the thickest 30 weight oils around.
- Can I use this oil even if my car manufacturer recommends a different weight? Great question. Your best bet would be to search or start a new topic if it hasn't been discussed. It should be fine if your car needs 0w-30 (Duh), 5w-30, or 10w-30. Personally, I wouldn't use GC if my car called for non-30 weight.
- Where can I buy this stuff? In the US, AutoZone is the only major store that carries GC. Most AutoZones carry it, but not all. In Canada, you can try your luck at AutoZone and Wally World.
- There are 3 types of GC.
- U.S. - So it's not really GC, but it's U.S. made Castrol Syntec 0w-30.
- Green - Yes, the oil is Green.
- Gold - The most recent stuff.
- What's the difference?
- There's not much research done on the U.S. stuff, so just don't buy it.
- Green vs Gold
- No one is 100% sure which is better.
- Green has proven itself to be great.
- So far, Gold has been great too!
- Gold is probably just as good as Green. (Maybe better?)
- Click here for more reading.
- The U.S. stuff probably isn't as good as the German stuff.
- Buy Green if you can find it. Otherwise go for the Gold!
- How can I tell the difference?
First, I'll teach you how to read the date codes.
- Look at the bottom of the bottle, it'll say something like M05216xxxx
- The 05 represents the year it was made. (2005 in this case)
- The 216 represents the day it was made. (001 - 365)
- No need to look at the date code, it'll say "Made in the U.S.A." on the back.
- It was last made in 2002, but many AutoZones still have some lying around.
- It'll say "Made in Germany" on the back.
- Anything until and including M05010xxxx is Green.
- This stuff came out in 2002.
- It'll say "Made in Germany" on the back.
- Anything after M05010xxxx is Gold.
- This is the current GC.
- Are you a chemical engineer or tribologist? Nope, just an enthusiast. I am an Electrical Engineer and I got A's in all my physics/chem classes. (I still don't know jack about those subjects.)
- Why do people hunt for Green GC so frivolously? I don't know. There's something novel about losing gas/time/money/relationships for the Green.
- What's the deal with the elves? Shhh, don't get involved. They'll pull you back in if you try to get out.
- sxg6 for the GC photos.
- AndyH for the cold viscosity table.
- 427Z06 for the viscosity comparisons.
- Everyone who gave me suggestions and caught my errors. If you think your name should be here, don't be shy and PM me!