Toyota FTS report engine issues with FR-S running 91 octane

[Calidrifter]

I'll try this out once my new ECU comes in as i literally live a few blocks from A 100 pump.

[Zadkiel]

I hope I don't jinx myself, but I haven't had any idling issues yet. I've only put Shell 93 in my car since I started to fill her up. It does cricket though, even with the V-Power.

[ahausheer]

OP please keep us updated as to any resolutions such as an ecu reflash. Thanks for the info

[Ben_G]

I know that the Subaru owner's manual says that "If unleaded gasoline with an octane rating of 93 AKI (98 RON) is not available, unleaded gasoline with an octane rating of 91 AKI (95 RON) may be used with no detriment to engine durability or driveability."

BUT...........
Subaru Canada website say that the recommended MINIMUM octane (AKI) (*required octane) is 93..... so perhaps the 91 Octane is pushing the limits a bit?

[ahausheer]

Originally Posted by Ben_G

I know that the Subaru owner's manual says that "If unleaded gasoline with an octane rating of 93 AKI (98 RON) is not available, unleaded gasoline with an octane rating of 91 AKI (95 RON) may be used with no detriment to engine durability or driveability."

BUT...........
Subaru Canada website say that the recommended MINIMUM octane (AKI) (*required octane) is 93..... so perhaps the 91 Octane is pushing the limits a bit?

Different ECU's?
Is 93 available universally in Canada?

[RandomHero]

Originally Posted by ahausheer

Different ECU's?
Is 93 available universally in Canada?

Yes but unless you are on the west coast all our 93 has ethanol which seems to bother these cars. Shell 91 is a popular option around here for ethanol free fuel.

[dyim]

So, is not using 93 the issue, or the presence of ethanol the issue?

[smbrm]

"...documented legitimate relations between rough engine idle and running conditions with using 91 octane fuel..."

I would be really curious for an explanation regarding the relationship of octane value to idle quality? Idling should in no way be challenging performance related to octane. I also wonder what rough running conditions actually means? I would suggest that this may be a hasty generalization?

[dyim]

Originally Posted by smbrm

"...documented legitimate relations between rough engine idle and running conditions with using 91 octane fuel..."

And I thought modern ECU can adjust ignition timing to compensate for lower octane so that there will be no knocking?

[smbrm]

Originally Posted by dyim

And I thought modern ECU can adjust ignition timing to compensate for lower octane so that there will be no knocking?

They do (up to a point), but they adjust based on the knock sensor, hearing(before the driver) knock. But I fail to understand the reason the sensors should be hearing knock at idle? So why should fuel "octane" to be affecting idle? Maybe another characteristic, other than "octane"? Petroleum fuels and lubricants are complex products with characteristics beyond those that we use to label differences(eg. octane), that are often not appreciated.

Also we have to remember that a vehicle is a system, so are vehicles designed to operate with available fuels, or are fuels designed to operate with available vehicles. The answer should be both!

The suggestion reported in the original note should be taken with a grain of salt until all the facts and evaluations are revealed.

[Reason]

All of my car life I have appreciated that on the west coast of Canada we can get 94 octane fuel with no ethanol at every Chevron location.

This just put it over the top.

It really sucks that some of you have no access to ethanol free 94 octane... and yes I am very surprised that Toyota did not consider this. Many automakers have had to deal with crappy east coast US/CAN fuel causing issues. Hell, the BMW M60 V8 had problems with Cylinder Liners pitting from the sulphur for years before they had to switch construction material and replace every longblock that had the problem...

I would not be surprised if there is a reflash to address this issue.