I've read that before too.. I think its BS. I'd bet 90% of WRX and STI owners run synthetic with no issues..
NASIOC is full of idiots and unfortunatly there are a metric shit ton of dealer personnel that are complete idiots as illustrated in the thread you supplied a link to. The things you need to find out before spending massive $'s on oil is as follows: 1. Does your engine consume oil as it is right now? 1a. What kind of condition is your engine is regardless of consumption? 2. Do you drive under conditions that the engine would benefit from synthetic oil? (race track/drag strip/autox/hot-cold-desert/extreme cold/heavy stop and go traffic/etc) 3. Can you afford synthetic?* 4. Can you afford to not to afford synthetic?* *Note that synthetic oil makers will advertise ridiculous increases in oil change intervals. The reality is that you STILL need to change the oil every 3months/3k miles or as recommended by the engine manufacture. That being said, I DO NOT recommend the 7500 mile interval on newer N/A SUBARUs. I always recommend the 3mo/3k mile interval. ESPECIALLY on the 'average' synthetics. The 'average' synthetic is no better than Castrol GTX. I also DO NOT recommend Mobil 1, Penzoil Platinum and Royal Purple. All of those seem to degrade fast and are quite thin. I cant say good or bad of the following: Castrol Syntec Valvoline synpower AMSOIL Total oils (good luck getting some of that in the USA, but I have seen it) Shell Rotella 5w40 synthetic Kendal GT1 Synthetic I use Motul in the Wife's WRX with GREAT success. ZERO consumption across a 5,000 mile change interval. I run 5k in that because it runs clean, does not see track/autox/stop go traffic or extreme temps. It's always come out clean as well. Never black/excessively dark. I was using it in my Legacy, but it consumes 2qts per 1000 miles due to internal issues caused by operator neglect (myself, overheating a long time ago) and other seals leaking that'll all be fixed in another 4x,xxx miles, so across 5k miles I have to put 10qts extra in. So every 5k miles I pay for 15qts. That's expensive at $8 a qt. So now I'm using the dealer's bulk oil which happens to be Kendal GT1 synthetic blend. Its been quite good in other cars, so far its doing good in the Legacy. Same consumption. So if you can afford $8x5 every 3k/5k miles, go for it. If you track/autox/stop-go traffic/extreme temps the thing, you should get synthetic. On the otherhand, if you feel that you need it but you consume MORE than 1qt per 1000 miles, you should consider figuring out the consumption issues and FIXING it first. It could be as simple as replacing the PCV valve, or worst case splitting the block and doing piston rings. I know on mine it'll likely be rings, hone/bore, pistons and all the seals in the engine. I'm hoping the bores are fine and I just need rings and a complete reseal. Anyhow...
I have run Mobile and Penzoil without any issues. When I run them in the summer I do run the 10w30 though and then switch over to 5w for the winter months. I have been using synthetic since around 60k miles and go through less than a quart per oil change (cept when the turbo seals were starting to go). Lately I have been trying the 0w30 stuff (usually advertised as european car formula) out since it is winter. No real change in oil usage and the car seems to like it.
I have been using Mobil 1 since the 2nd oil change and never had a problem coming up to 60k miles. My care burns very little oil off. After 3000 miles my oil level is still damn close to full.
I used Mobil 1 for a couple oil changes. Now I'm using Royal Purple, after every oil change my emptied oil fills up the 4 empty quarts almost completely.