Hey Y'all,
I am new to the forum and I got my '05 GMC Sierra D/A CC SB 4x4 on Friday. I traded an '02 Silverado D/A EC SB 4x4 in on it. I really enjoyed my '02. Good truck.:D I hope that I do not experience some of the problems with the lly that I have read in this forum. I have learned a lot by reading the forum over the past few months. I plan to keep my truck pretty much stock. I have already installed a K&N filter and I think I would like to get a bigger exhaust system and ditch the catylatic converter in the future, but for now I plan to enjoy my new truck! Now that I have said all of that, I have a couple of questions. How many of you recommend synthetic fluids for diesels and which, if any, factory fluids are synthetic?
Thanks in advance!!

Congrats on the new truck. I wouldn't worry too much about the trouble you read about. It represents a very small amount of trucks. I see more people post about troubles than good days of operation. Its human nature.

I have used AmsOil in my last 2 trucks both diesel, and will be putting it in this one once I hit 3k or whenever the rings seat, which ever comes first. I have been very impressed with how it stands up. I have used the bypass filter system with oil analysis at regular intervals. The testing was able to tell me of a fuel leak in my engine before I knew I had a problem. They say the oil can go 100K with regular bypass filter changes and oil analysis. I am not a dealer of AmsOil but I am sure you can find one around. I lucked out my buddy is a dealer so he gets me my stuff. I have heard good things of Mobil 1 but I like the full service of AmsOil, grease, oil, tranny fluid and gear oil all done in AmsOil. Even the air filter. Not to be an AmsOil commercial, but I like the stuff. Well I suppose this is more than $.02, but I was on a roll!! ):h

I put synthetics everywhere including grease. Note, that you should check ALL your fluids in the front end / rear end etc. as all of the trucks have come from the factory short on fluids. Take it back and make the dealer fill Er up with fluids and grease it thoroughly.

Use a oil that meets the certifications set forth in your owners manual (the diesel supplement that you should have received when you took delivery) I run Shell Rotella T, 15-40 and change it out ever 5K miles. Do all you can to prevent having your warranty voided should a few parts bind up on themselves.

Do a search on the forum, lots of intel on oils. Also, bobstheoilguy.com's website has good intel as well. I've gone to synthetics in the differentials, engine when over 10k miles, most like Mobil Delvac 1. JJ

Cowdoc,

In answer to the last part of your question, which factory fuilds are synthetic, the rear end has the synthetic grape juice. Some think, including me, that the front end has had synthetic grape juice since mid 2004. Others say it is conventional. Remove the plug from the front and take a small sample, then smell it. If it smells like grape juice, then is most likely synthetic. I don't think any conventional oil has that smell.

(I wonder if GM made it with that smell so it is easy to tell the synthetic from conventional??)