Famduke Posted May 28, 2021 Share Posted May 28, 2021 I have never been told that I need to run anything higher than 87 Octane in my Legacy Touring Turbo. However, I have read that most turbos require higher than regular unleaded. What is the situation with this one? Thanks! Link to comment Share on other sites More sharing options...
caddygti16v Posted May 28, 2021 Share Posted May 28, 2021 It's 87 only, no benefits with premium fuel, the ecu doesn't adjust for higher octane. Sent from my Pixel 2 using Tapatalk Link to comment Share on other sites More sharing options...
xt2005bonbon Posted May 28, 2021 Share Posted May 28, 2021 I found the official brochure and it does show the fuel mileage rating for 87 octane. I am really surprised. I mean, this is a turbocharged engine which should really benefit from higher octane gas. More timing = more power. So, they must have 'detuned' it from the factory and optimized it to run with an 87 octane gas. If one day you are able to tune the ECU and increase timing, then you should see a little increase in torque when using 93. Link to comment Share on other sites More sharing options...
whitetiger Posted May 28, 2021 Share Posted May 28, 2021 direct injection allows for lower octane fuel to be used without having to pull back timing for knock, and subaru used this to aid fuel economy for both range, and the ability to used 87oct. i'm sure more power can be made with a tune made for 93, but subaru didn't push that boundary, so 87 is all that is needed. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted May 28, 2021 Share Posted May 28, 2021 I think they probably will with the next Sti. We shall see. Link to comment Share on other sites More sharing options...
whitetiger Posted May 28, 2021 Share Posted May 28, 2021 yes, with a rumored 400hp, of course they will require 91+, but since the CVT in the legacy disintegrates past a stage 1 tune as evidenced on the FA20 VCT wrx, subaru has no need for anything beyond 87 on the legacy/outback XT. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted May 28, 2021 Share Posted May 28, 2021 Interesting that they do require premium for the FA20 DIT though. I guess if they did not, then the WRX power rating would be noticeably lower. So yeah, they must have definitely 'detuned' the outback/legacy XT a bit, as you said, probably to save the CVT. There are probably other reasons too. Here are the brochures I referred to btw. https://www.subaru.com/content/dam/subaru/downloads/pdf/brochures/2019/WRX/2019_Subaru_WRX.pdf https://www.subaru.com/content/dam/subaru/downloads/pdf/brochures/2021/legacy/2021_Subaru_Legacy_Brochure.pdf Link to comment Share on other sites More sharing options...
whitetiger Posted May 28, 2021 Share Posted May 28, 2021 the fa20 has less displacement, but essentially the same power output of the FA24 in the XT vehicles. its reasonable to assume the FA20 needs more timing advance to attain that power level, and therefore more knock resistance. Link to comment Share on other sites More sharing options...
xt2005bonbon Posted May 28, 2021 Share Posted May 28, 2021 That's right. I actually wonder if these FA24 would fit in our car with our manual trans. That would be sweet. Somebody will do this one day. Link to comment Share on other sites More sharing options...
whitetiger Posted May 28, 2021 Share Posted May 28, 2021 the sti FA24DIT coming out will undoubtedly be the target candidate for anyone's transplant dreams. Link to comment Share on other sites More sharing options...
laufu Posted May 28, 2021 Share Posted May 28, 2021 You guys should check out the Ascent forums. Cobb Tuning posted this nice summary regarding tuning the Ascent. https://www.ascentforums.com/threads/cobb-tuning-for-subaru-ascent.7937/post-148424 Link to comment Share on other sites More sharing options...
whitetiger Posted May 28, 2021 Share Posted May 28, 2021 ^yeah, anything past stage 1 and cvt goes "no thanks" Link to comment Share on other sites More sharing options...
caddygti16v Posted May 28, 2021 Share Posted May 28, 2021 Many peeps might be happy with just a "driveability" tune but not sure I would chance it. My nearest dealer already cried warranty when I mentioned of doing my own maintenance. [emoji849] Sent from my Pixel 2 using Tapatalk Link to comment Share on other sites More sharing options...
Bill G. Posted May 31, 2021 Share Posted May 31, 2021 The "regular gas with a turbo" thing is actually a XT selling point (per my Subaru salesman). Link to comment Share on other sites More sharing options...
xt2005bonbon Posted June 1, 2021 Share Posted June 1, 2021 I can definitely see that, especially with the price of gas going up now. Link to comment Share on other sites More sharing options...
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