Noob Q: Does my Legacy Turbo need premium fuel?

[MacNews]

I have some noob questions about the turbocharger on my Legacy:

1. The turbocharger requires premium fuel right?

2. What octane level is considered 'premium'? The very best 93? Or will 91 be sufficient?

3. Will using regular gasoline damage the turbo instantly or will it take time?

[Legacy777]

A minimum of 91 octane is recommended by the owner's manual.

87 octane can be used, but the manual recommends only using it temporarily as it may lead to engine knocking.

[MacNews]

Thanks Legacy777!

[Hardware89]

the best octane is 100 but that rare at most gas stations so just go with 91

[GeneralDisorder]

I have some noob questions about the turbocharger on my Legacy:

1. The turbocharger requires premium fuel right?

That's not correct - the ENGINE requires premium fuel because of the attainable cylinder pressures while under boost from the turbo. The turbo itself requires oil and coolant... and exhaust of course. But it cares not if you are running gasoline of poor quality and frankly wouldn't care if you ran deisel or hydrogen.

2. What octane level is considered 'premium'? The very best 93? Or will 91 be sufficient?

91 by the way we rate fuels in the US.... (RON+MON)/2

3. Will using regular gasoline damage the turbo instantly or will it take time?

It won't cause damage to anything "instantly", what it will cause is the ECU to retard the ignition timing and give you poor performance. It will eventually lead to engine deposits that will increase cylinder pressures further and cause it to ping even while using premium fuel.

You will actually get better fuel economy with premium and that largely offsets the added cost of the fuel. There's no win for buying cheap gas on performance minded engines that run forced induction. You are just slow and inneficient and unhappy.

GD