Originally Posted By: markhait
Whats a used oil analysis? They didn't show me anything, but they said that they tore the engine apart and removed all the sludge. Thats kind of why I think I have that dreaded piston slap. For the dealer to take 2 days and take the engine apart and keep finding things to be replaced, I suspect that there are bigger issues that GM doesn't want to pay for and so they replace enough to get you running again. I've read on several forums that the engine should be replaced if you have piston slap.
What baffles me is the sudden oil consumption I was experiencing. I never had to add as much as 1/2 quart in a year before and now I'm adding 1 quart/month. I'm confused.
markhait,
So it appears that you've now figured out what a used oil analysis is and you've also requested your oil sample kit. However, I wouldn't recommend that you take a sample of oil from your truck just yet...
As others have said, since GM has just repaired your engine, the used oil analysis will not find anything surprising that may have been there before. Also, the used oil analysis will find dirt, silicone sealant, antifreeze, etc from the teardown that still exist in the oil that GM filled your truck with. These findings will give you the false assertion that something is still wrong with your truck, whereas there may be nothing wrong in reality.
What I would recommend you do is this:
1. Drive your truck for a 1-2k miles, then change out the oil and filter with some more conventional oil of the correct grade (5W30 or 10W30)
2. Do this again 1-3k miles later.
3. Fill with the oil of your choice (Amsoil if you want to give them a shot again). Reset the oil change indicator to 100%.
4. Drive until your oil change light appears. At this time, change the oil. However, be sure to take a sample of hot oil as it is falling out of your oil drain hole. Do not take the sample out of your catch basin as there may be contamination or dirt present in there.
5. Fill the truck with new oil and reset the indicator again. In the meantime, wait for your oil sample results to come back.
Once the used oil analysis comes back, post it up here and people can help you decipher the comments and findings to determine if your engine can or cannot go farther on it's fill of synthetic oil. There may be issues with your new truck that were not present on your old truck that will not allow it to go the full 25k that Amsoil states.
Remember, Amsoil is a great product, as are many other high end synthetics on the market. I believe their products are top notch, and have used them for years (as well as other high end synthetics). They have always performed to my satisfaction. Amsoil can and does go 25k in ideal cases, and has proven to work well under extended drains. HOWEVER... You need to make sure that it will work in your scenario with a used oil analysis to rest assured that you are making the right decision. I know that in my engine, Amsoil or any other synthetic for that matter will not last more than 10k. Period. No questions there. So I limit myself to 10k change intervals (or less if desired). I am happy with this, and you may have to do the same if your engine cannot support 25k drain intervals.
Remember, always use used oil analysis to determine a SAFE extended interval for your truck in your particular scenario. Hopefully this helps. Good luck!
