[Hydrochloric]

in my old 300m, i used 93 and the extra mileage washed the cost. but the 93 bumped my long term timing maps up and anytime id put 87 in it, the car would run terrible the next 100 miles until it relearned. running higher octane gas will let your car advance timing further and pick up some performance and mileage to an extent. most people argue this because they think the results are instant, they arent, the ecu takes time to readjust its maps.

That depends entirely on the car, though. Our old ECUs have a max timing map, and a small amount of adjustment per cell. They won't gain any benefit from anything above 89 (and possibly not from that either). Newer cars are different and can dynamically adjust timing to account for fuel quality.

 

[TerryJr]

when i disabled my knock sensor, i was pulling 15 degrees of timing put at wot and was still in the mid 20s. the limits pretty high, on a 97 ecu anyway

 

[gf8Andy]

87 and sometimes 89. used 91 when gas prices were down

 

[Hydrochloric]

when i disabled my knock sensor, i was pulling 15 degrees of timing put at wot and was still in the mid 20s. the limits pretty high, on a 97 ecu anyway

Should be +/- 15*. At high RPM the piston speeds are very high and the timing has to be pretty advanced for the flame front to expand fast enough to do sufficient work, so that sounds reasonable to me. In my car, at 6000RPM and 4 PSI, it runs 39*. Take 15 off that and you're at 24.

 

[Padraig]

91

91. I know what the manual says, and I know the facts also. But, I just feel the car runs smoother, so it make me feel better.

 

[TerryJr]

today E30, yesterday e80. Had to pump some 93 this mornign to get me by til the Hulton Bridge reopens

 

[DN1911]

Ethonal free 91 octane premium here in western CO! Both my 95 Legacy and my 2016 3.5 Ecoboost F150 run better and getter fuel mileage with it

 

[drummerRS2505]

91-93 on my pump map when needed.

Most of the time E85 baby! : ) Not my everyday car, but i can drive it often with no problems just not the best mileage!

 

[jeff6666p]

Always 93 since I bought her.

 

[Jack_Stalk]

Ive always used 87 for NA, and tuned on 91 for my turbo cars

 

[steezin_and_wheezin]

93 for the yoshio ecu, Pure station(e-free)

Still on that 93 Pure (e-free), but now running through the ej205

 

[Gc8fanboi]

Mixing e85 and 87 octane. Car feels a little more powerful but engine mainly feels smoother than just using 87. My01 RS, stock tune

 

[GuardsRed25rs]

91 shell

 

[Tonyclinard]

What about e85 is it ok to run?

 

[Brock]

What about e85 is it ok to run?

If you have a way to get the right amount of fuel:air in, yes.

Here's a thread I wrote about it many years ago: https://www.rs25.com/forums/f5/t208728-na-e85-thread.html