Synthetic Oil

Oil viscosity and conventional vs synthetic are still some of the more hotly contested topics in many forums. Bottom line - there is no one size fits all answer. There will be some experimentation needed on your part to find the right oil for "your" car. Haven't even touched the additive package aspect - as that can be more involved. For more info - BITOG forums are a good place to start to get your lubricity and tribological fix.

Toyota originally recommended a 5w-30 for this model year - though it changed it in 2007, when they spec'd 5w-20 as a good, fuel saving alternative for all the 9th gen Corollas. All convention oil with the 5K mile change interval.

Completely up to you on what brand and oil viscosity to run - your car will let you know what it likes to run. Some prefer to run a little heavier oil, trading a little MPG for a thicker oil film and more oil pressure. Some rather maximize economy and run as thin as possible, trading a little of that oil cushion for an extra couple of MPG.

Also have to note that different oil manufacturers have a large variance in oil viscosity. Some 5w-30 tend to run on the lower range of this grade - like Mobil 1 and Valvoline. Some run higher in the scale - like Amsoil and Pennzoil Platinum. Some oils change viscosity when run in the engine - some shear down much thinner (Mobil 1 has a tendency to do this), some actually shear up (Amsoil) meaning they get thicker as they are run.

Each engine will run the oil a bit differently - some like high shear resistant oils, some don't. I know on my Corolla, on extended oil drains (7500-10K miles) - I can see a fill of Mobil 1 5w-30 shear down to almost a 20 weight oil. On the opposite end, I had run Amsoil 0w-30 which sheared up to nearly a 40 weight over the same drain interval.

Granted, the difference in "thickness" between a 20 weight and 40 weight is not that much - as viscosity is highly tied to temperature. A 40 weight is not twice as thick as a 20 weight - which makes it hard to really pick a good oil. Just to put it in perspective - a 20 weight oil at 190 degrees is about a thick as a 40 weight oil at 230 degrees (approximation). At normal temperatures - oil viscosity between the ones you listed is hardly that much different. But at very cold temperatures - you might see a thicker oil cause the engine to labor on initial start-up.

5w-30 and 0w-30 are spec'd to run as a 30 weight when "hot". 5w and 0w designation indicates how the oil will react at low temperatures - 5 weight in "w" - winter, vs a 0 weight. 5w-30 and 0w-30 runs pretty much the same at normal temperatures, but at sub zero temps - your engine will crank more easily with a 0w-30 vs a 5w-30.

Start with what you have in it now. Then try a grade up and down and see what it does. Synthetic is not a magic bullet - will not make the car last any longer than a well maintained car running conventional. Just that there are certain properties of synthetic oil that makes it well suited for specific purposes, extended oil drain intervals is one of them. If you don't plan on extending the drain interval on the car and pulling periodic UOAs to check on progress, then running synthetic will likely only hurt your wallet more than gain benefits anywhere else.

Depends on which forum you ask that question. No doubt - both are solid synthetic oils. There have been a number of UOA and VOA studies on the oils. Ancedotal evidence from personal experience on which one is better and why. Lots of standardized testing that show sometimes stunning results.

Myself - I didn't see the advantage of running Amsoil. Cost to performance, the math just didn't work out for my needs. The ability to grab Mobil 1, Valvoline Synpower, or other synthetics from almost any automotive outlet, Walmart, etc. - just made more sense to use sometime else. I will caveat that from a personal standpoint, I did have a catastrophic experience with Amsoil. Used to run it in a company dirt track car a couple of decades ago. These were Sprint cars - basically a go cart with a huge wing and a V8 engine to power them. Small block massaged by the legendary John Lingenfelter - had two engine that saw two races each - usually they are good for four before then they get torn down for inspection. Both were filled with Redline engine oil as the shop had great success with that oil. One of the drivers wanted to run Amsoil - as he was a big fan of it, figured that the company could get sponsored and we'd all be able to get a discount on oil.

Turned out, with this single crankcase full of oil - the car didn't even finish the race. Engine grenaded, bearings were wiped from lack of oil film, cases of metal galling. The other engine/car finished, no problems. Unfortunately, we couldn't prove it was oil related - so Amsoil wouldn't cover the cost of the $40K engine / powertrain replacement. The lead engine mechanic was convinced that it was oil related, as he never saw that sort of damage before this time. We never used Amsoil from that point on. Just to turn a screw a bit - that other engine, the shop still runs it to this day - Redline oil exclusively. There have been engines that let go since that time, but none ever spectacularly blew up like that one.