I talked with someone today about my planned switch to Mobil 1. He said that the only downside to using 100% synthetic is if the engine is not run regularly, then the oil will not stay on the cylinder walls as it does with dino oil. Since my Z is a second car, and I hope for it to never see snow or rain, is this a bad idea? The car does sit for long periods of time without being driven thanks to the crappy weather here in Ohio. Should I stick with only part synthetic as my friend suggests?

 

part synthetic is like part pregnant- it's all or nothin' baby!!!!
Most synthetics contain additives which coat the cylinder walls and stay put.
Personally, I have decided to leave Mobil 1 and Castrol Syntec land and go with AMSOil 5W30 in my Z.
I use synthetics in all my vehicles and have for 15 years- would not have anything else in there after break-in!!!!!!

 

So when Mobil1 says that it is 100% synthetic, you think it still has additives?

 

Mobil 1 and Castrol both market "blends" and "full" synthetic. "Full" synthetic isn't what you would expect it to be though. There are several threads that discuss this, if you want to search.
AMSOil and Redline are different- their specs are much better. Royal Purple seems to run a close 3rd to them.

I am going to continue using Castrol Syntec in my other vehicles, but the Z is getting AMSOil.

 

My understanding is that synthetics leave a film on all metal surfaces which will protect them better than conventional oils. Synthetics also lubricate more quickly at start up thereby again reducing wear. I do believe that it is best to run conventional oils during break-in to help properly seat rings et al, and then switch to synthetics. Semi-synthetics, though superior to conventional oils don't in my opinion justify the cost difference. If your going synthetic go 100%.

 

So many people have so much disinformation about synthetic.

Why would a lot of expensive sports cars come from the factory with synthetic if it wasn't good stuff? Vettes, AMG Mercedes, Porsches, etc.

Have you seen the difference of a 100,000+ mile engine run on synthetic vs regular oil? Regular oil, if changed frequently can leave the engine in good shape. Synthetic can leave it looking nearly new.

I'm running Mobil 1 0w30 in my 91 turbo Syclone with only 18,000 miles on it. I have no lack of trust in the oil (and new, it was required for warranty reasons by GMC)

 

here is the definition of synthetic:

"synthetic oils

Oils produced by synthesis (chemical reaction) rather than by extraction or refinement.
Many (but not all) synthetic oils offer immense advantages in terms of high temperature stability and low temperature fluidity, but are more costly than mineral oils.
Major advantage of all synthetic oils their chemical unformity.

The "100% Synthetic" relates to the Base Oil or Base Stock, it and only it (the Base Stock) is synthetically made. In case of Mobil 1, it was originally PAO (Poly-alpha-olefin).

The "exclusive of carrier oil" means in English that the Carrier or the Process Oil that is used to "carry" the additives is not synthetic oil and therefore, the final product (Motor Oil)
is NOT 100% Synthetic, even though the Base Oil is 100% Synthetic."

Buy it for it's uniformity and ability to handle excesses of heat and cold.