Originally Posted by ghostrider25

I know there are alot of people debating 5w-30 or 10w-30 on startup 10w-30 will be slower to reach the head of the engine but in hindsight it will also leak down from the head slower and bind to engine internals longer before draining into the oil pan. From what I understand our engines are pretty high compression and on startup need oil to the head fast so the lighter factory weight will reach the head faster. It will also circulate through the engine faster because it is lighter causing less stress on the oil pump. I'm not saying that the pump cannot handle 10w-30 by any means though. I would like to add in colder areas like colorado or new york new jersey vermont and so on in the winter 10w-30 will be alot thicker and you could possibly damage engine components. You should also see a loss in fuel economy by switching to the heavier oil of course most people in the forums have done enough mods to their cars that fuel economy isn't exactly a priority. I would say stay with what the factory recomends just switch to a synthetic. The engine desighners at toyota seem to be very intelligent and I'm sure they chose the oil weight for a good reason. the only time I could see swithcing to 10w-30 would be in a scion with over 100 thousand miles on it. In this situation there would be engine wear and wear on the cylinder walls and in the head that may actually benifit from a little bit heavier oil but even that may be dissproven I might also consider a heavier oil in a turbo or supercharger application during warm months. I would do research on high compression engines and heavier weight oil to make my final decision. Ultimatly it's your car and your choice let us know how it goes.

Originally Posted by CrimiNole03

whenever i switch to synthetic... I'm going to do an oil analysis every so often to see if the oil is performing as it should (AMSOIL 5w-30 25k drain interval) ...

Originally Posted by vintage42

I was an Amsoil dealer for several years. Used it in my cars and bikes and sold it at bike rallies:
http://www.flickr.com/photos/roundel/21925669/

I would not do what you propose. The 25K interval will require a couple of messy filter changes using the special expensive Amsoil regular full-flow filters. The oil will still become very black, as filtering does not remove the finest particles that cause color.

If I remember correctly, the 25K drain interval may actually be for vehicles with a second Amsoil bypass oil filter, that filters the oil a drop at a time. There is no room for that item under the xB hood. Also, doing the oil analysis of the dregs in the regular filter is not cheap. That whole protocol of the two filters and analysis is good for crude commercial vehicles with large oil sumps where you have a dozen quarts invested, but I don't think it is appropriate for the xB with it's motorcycle-like jewel of an engine.

Originally Posted by ghostrider25

here is a silly question how long can you run synthetic say mobil on a factory oil filter safely will it go five thousand miles without a problem driving hard.

Originally Posted by gade202

I'd like to throw my 2 cents into the pot here...

I was given a 94 Buick Regal 3.8L V6 back in 2003 with 112k miles. It had ran dino oil all it's life. I switched to Mobil 1 Extended w/ Mobil 1 filter and changed every 10k miles. The engine is now at 183k miles and getting about 24MPG, as opposed to 19-20MPG when I started drivning it.

I have a 06 Scion xA on the way that I plan on switching to synthetic at 1k and changing every 7.5k. Why? Synthetic oil has an extended wear period. That is a fact. It has other benefits but in my eyes, that's the main reason to use it. The arguement about particles in the oil is a vaild one, but it's been misguided to the oil. If you are worried about particles in the oil, change the filter every 5k miles. Anything small enough to pass though the filter won't do much besides make the oil a little darker. That's a cheap, fool proof solution to allow you to use synthetic oil for it's intended purpose.