Can I mix different synthetic oils? For example, Amsoil TSO and Mobil 1.

 

You can do anything you want, but why bother mixing synthetic oils? A more common practice is to mix synthetic oil with dino oil to get your own syn-blend. Syn-blends being marketed today are only in the order of 10% synthetic oil and are a waste of money.

I don't know what advantage you are trying to achieve by mixing synthetic oils, unless its only because you don't have enough of each type for a full oil change and even then I wouldn't do it.

 

you can, but i would just run em straight, they may have certain additives that get angry with each other....

 

I mixed bunch of times. When I ran out of Amsoil during an oil change, I went to the store and bought some Mobil1 to use.

 

yes you can mix synthetic/synthetic or synthetic/dino...no matter what brand...

and there is no harm in going back to dino oil after using synthetic...it also applies to the other way around

 

As a general rule, you will be better off by using the same oil from the same manufacturer. But rules are to be broken. I got some cheap Mobil 1 synthetic 0W30 that I mix in with Mobil 1 synthetic 5W30 oil when I change oil for going into the winter (I don't use the lighter weight in the summer).

I also had some, but not enough of, an earlier synthetic oil that I mixed (one time) with Mobil 1 of the same weight when I decided to start using Mobil 1. Was not going to just leave the old oil (no longer available) sitting on the shelf, so I used it.

Most of the time, you should probably follow the rule above, but the call is yours. If you don't you probably won't hurt anything. Why is this a good rule to follow: different motor oil manufacturers use different addative packages for their oils. The difference in these packages could (but not likely) cause some problem, more likely if you continue to make these blends with every oil change.

If you don't have enough Amsoil for a change, you are better off making up the difference with Mobil 1 than not filling the crankcase so you are less than a quart below the full line.