lammydi,
This will open a can of worms....
Mobil 1 has had slightly higher wear indicators than Amsoil (but I do mean slight) and about the same as Royal Purple and is well within statistical range of both of them on most of the UOA’s that I have seen or had done. Amsoil is WAY too high priced for me as is Royal Purple when I can buy 5 gallon jugs of Mobil 1 at Wally World for $23 to $24 dollars (when I bought them a few months ago). I like the higher temp ranges without viscosity shearing that I can get from synthetic oils and tend to prefer them but the other synthetics such as Pennzoil Platinum, German Castrol, and several others work just as well.
The main drawback (to me) with Royal Purple and Amsoil is the lack of API approval and that pesky little seal on the bottle. I know that the burden of proof on a warranty claim lies with Toyota but I don't feel like giving them a freebie by not using API certified oil. They might have them certified by now but I have not heard or seen anything to that effect. Edit: It appears that Royal Purple is API certified. Amsoil still has just one of it's lines certified with the remainder not certified. Make sure you know what you are buying....
There has been a lot of discussion on bitog about these oils, certifications, UOA's, oil change intervals, oil and air filter efficiency and their effect on engine wear. With a lot of current and retired lubrication chemists and technicians on that forum, they can talk for days about the differences but when you get down to it, given a 5,000 mile OCI, using any GOOD quality dino or synthetic oil and a good oil filter will work equally well.
Once you are out of the warranty period, synthetic oil can be used for extended oil change intervals to the tune of 10,000 to 20,000 miles. The guys running these long periods are mostly using Amsoil and Mobil 1 EP oils and do a UOA every 5,000 miles or so and change the oil when the TBN (which indicates how much of the additive package is left) drops down to a low number. I do not run extended intervals once the warranty is out (I guess I’m still old school) and run standard Mobil 1 instead of EP.
In case you are wondering, I currently have over 120 quarts of 5w-20 Mobil 1 and roughly 40 Mobil 1 oil filters. It sounds like a lot but it will not last long with the cars our family keeps on the road. When the oil filters are gone, I will be switching back to Wix filters for the price point difference. I am still up in the air about the oil and will probably stick with Mobil 1 but Pennzoil Platinum has some impressive numbers and a nice price in the store.
Hope this helps...
