Amsoil, Royal Purple, Mobil 1?

I'm planning to flush and change the transmission oil this wknd.
My VX has 50,000 miles. Took my VX to Kwik Kar Lube (they usually carry Royal Purple). The guy at the shop told me the following:

- Mobil 1 is a very good oil
- Royal Purple is excellent
- Amsoil is the best !!!

Between Royal Purple and Amsoil, which in your opinion is the best? Any experiences with Amsoil out there?

Is there any other oil I need to replace?

By the way, last time I used Royal Purple in my engine. The sticker said to replace it after 3,000 miles. This time they were out of R.P., so I used Mobil 1. Now the sticker says to change it after 6,000 miles. I thought both were synthetic...

1. Why the difference between changes? Is the information correct?
2.- Is it safe for the engine to use different brands? Someone told me that it is not good for the engine.

Thanks!

No personal experience with Royal Purple yet. Have had nothing but positive experiences with AMSoil... not just the products but also getting information from them. Last time I wrote them I got a response the next morning.

Before finding out about AMSoil I used Mobil 1 religiously... it's OK. Tried Redline too and that was about the same. Both are good.

You're making oil changes far too complicated for yourself. Check your VX's owner's manual for factory recommended service intervals and service items. If you don't have a manual I think the manual package can be purchased from any Isuzu dealer for around $30 to $35.

Different brands have different additives. Mixing brands may cause unwanted chemical recations (unlikely). But to be safe, it's best to stick to one brand... if you do have to mix temporarily, I don't think it would cause any long term harm.