TomQ

just wondering what's better for my car ?
Castrol GTX SAE 10W-30 or 5W-30 ?
i live in San Francisco and drive 2001 Trans am
<img src="graemlins/z06.gif" border="0" alt="[Z06 Corvette]" />

mmiller

iTrader: (1)

Any of the major oil manufacturers are fine. I don't think one is really better than another. I would go with 5w 30 since you live in somewhat of a cold environment. The thinner 5 weight oil at start up should be better for you.

Supertrapped

I like Mobil 1 10w-30 in my Formula. I put Castrol in my Firebird and GTO though <img src="gr_stretch.gif" border="0">

Red Dragon

i have used Mobil 1 5w 30 since my first oil change(3000 miles) not a problem since <img src="gr_images/icons/cool.gif" border="0">

TA_2001

castrol 10w30 here in north texas (HOT) I have never let the oil get dark, car has 16K
Here is an oil poll

http://ls1info.com/pollBooth.php?op=...&order=&thold=

DCPunkSteve

Well I do alot of my own testing since I don't take anybodys word for anything. Heres something that I found interesting. I took Valvoline, Castrol, Mobil 1, Royal Purple, and Penzoil, and I tried some of those tests you see in the comercial. I took them all and put them in a pan, and held it over an oxyfuel torch for a while
1. Mobil 1 got dark but flowed pretty good, and coated the pan pretty good, with a little smoke.
2. Penzoil also got really dark, still flowed, still coated but was smoking pretty good.
3. Royal Purple, flowed and coated great, smoked a little, but I think it held up better than the Mobil 1.
4. Valvoline, got a little thicker, smoked pretty good, but held up okay, I wouldn't use it for an LS1 though.
5. Castrol caught fire! <img src="gr_eek2.gif" border="0"> wouldn't want that in my engine. Not only did it catch fire, but it did so in a flash. It started to smoke, never got thick, but just caught fire.
Keep in mind that these are some pretty severe conditions, and that any engine reaching these temperatures would more than likely fail anyway, but it's something to keep in mind. On the other hand Castrol was the best flowing oil comming out of the hard freezer (wich is -40*F) fallowed buy Royal Purple, and Mobil 1, with Valvoline and Penzoil comming up last. All tests were done with 5w30 synthetic with the exception of Royal Purple.