I have a quick question about high octane fuel in a stock EVO. I have a 2006 EVO IX, currently bone stock, and was wondering if I'll cause any damage by filling up a gallon or two of 101 octane mixed with 91? Last night I decided to put 1.5 gallons of 101 with the rest of the tank filled with 91. Everything seems fine but I wanted to know if it's bad since I'm not tuned or anything for it.
Thanks in advance for any replys!

 

if the 101 is unleaded your fine

 

ok cool then I should be fine.

 

^^^ if you were running leaded all the time, it would build up some deposits in your engine but usually only on the cat will the lead do any damage. and that even takes several full tanks.

no tune needed. but to get gains from it would require tuning or upping the boost. it shouldn't make much of a difference for a stock evo, even on 91. evos run rich and out of the factory have no knock. when the ecu sees knock it pulls timing and slows down the car. higher octane gets rid of knock allowing to push more boost or leaner AFRs. although i our cars go into a safer mode with 91 and it pulls timing. so it does help, but not much.

 

unleaded 101 is fine for a stock car... but pretty much useless.

 

leaded 101 will eat up o2 sensors.
unleaded 101 will burn slower causing carbon deposits to build up due to not completly burning all the fuel in the combustion chambers.

 

Carbon deposits? should I stop using 101 then? I was planing on running 101 with every tank of gas.

 

with a mix of 1.5 gal of 101 and 12.5 gal of 91, your effective octane rating is only 92. The same pump gas that I run in my car every day. You won't run into any problems (as long as you stay away from leaded fuel), but you're also basically not gaining much either.

 

Good point, yah don't run it unless your going to turn up your boost.

 

You are fine running a mix of 91 and 101. The gas in California sucks big time. I would do the same thing if I lived there.

 

Even better point. Run it.

 

As a recommendation check up on the how to section on how to boost octane. Toulene i think is what it is called and am thinking of trying this to mix for cheaper.

 

normally i stay away from these questions, but talk about misinformation- jesus, guys...

i think anyone who's telling you you're wasting your time must live in places with real gas, or i they need to read your post bit more slowly.

mixing a few gallons of 101 into your west coast special-91 octane will work quite nicely. yes, even in a bone stock car. unless there's something very different about the IX, the stock ecu works at peak performance at around 93-94 octane. This has been dyno tested, verified, and published on this site.

the can will run on 91, but treats it like any other cheap, crappy gas you decide to dump in: it pulls timing in the upper ranges (above ~5500rpm in my car) to prevent detonation. the higly adaptable ECU's in modern cars are what allow oil comanies to sell us this 91 crap in the first place.

get the octane up into it's optimal range, and you won't feel the same hesitation at WOT over 5k. it's that simple. there are several calculators online:

http://www.ranney.com/~mjr/fuel_blend.html

anything over ~94 octane is probably a waste, since, at least as far i've seen documented, the ECU isn't optimized for it.

but to imply that it's "useless" or that you're going to get "carbon deposits" by simply mixing a few gallons of 101 into 91? spare me, guys. really.

a little information is a dangerous thing, clearly...

 

Quite.

geminix3 is completey accurate. Raising the effective octane to 93/94 will
definitely help.

d

 

prolly should have asked the question BEFORE you put 101 in your car, huh? LoL.