94 octane gas (for n/a EJ25)
07-13-2004, 07:46 PM
#1
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Join Date: Oct 2003
Posts: 8
94 octane gas (for n/a EJ25)
i just start put in 94 octane to my 2.5rs. Some people say is good and some say is bad???? but for me i think it run smoother than before. and i heard not all the car could use 94oct???? could any of you guys, give me an answer. THanks
07-14-2004, 02:07 PM
#2
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all of soa's turbo charged cars require 91 octane. the n a cars only require 87 octane. you are wasting money by puting in a high octane gas. the higher the octane the harder it is to make it burn. high compression engines will lightoff the fuel/air mixture before the plug sparks (engine knock). personaly i find my cars run better after a wash and wax. seriously it's good that you want the best for your rs you might consider going up just 1 grade to ensure that the octane does not drop below what the pump states. save that extra money to help with some upgrades.
07-14-2004, 02:21 PM
#4
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Join Date: Feb 2004
Location: The Hunted Forest
Posts: 720
Car Info: Mazda Protege '02 (Wishing protege has AWD and a H6 twin turbo)
Originally Posted by nic3krnnamja83
nothing wrong in running 94 except the price
07-17-2004, 02:24 PM
#5
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Join Date: Nov 2002
Posts: 56
Originally Posted by 2.5RS
i just start put in 94 octane to my 2.5rs. Some people say is good and some say is bad???? but for me i think it run smoother than before. and i heard not all the car could use 94oct???? could any of you guys, give me an answer. THanks
It'll appear to run smoother, yes. I noticed this in my 1997 Outback Sport as well. You are probably actually losing power. How do I know? I tested it at the dragstrip in both my Subarus. Even went as far as putting in 100 octane from the track. Throttle response seemed to improve and it ran much smoother BUT my 1/4 mile times were slower in both cases (Subaru XT6 and OBS).
If you want to take advantage of higher octane, don't go so high. Since stock is 87, go with 89 octane. It'll enable your ECU to bump up timing slightly so you can take advantage of it. Our car's timing is pretty aggressive. How do I know? I checked it out with a Pocketlogger on my Palm Pilot. How much was timing bumped up before and after using higher octane. I can not remember. Maybe 4-5 degrees or so. However, my OBS seems to run best at 89 octane rather than 87. 89 octane again will enable your ECU to run more advanced timing. 87 octane will probably experience some pinging in some situations (Very hot day, high load from extra people, etc) so timing will be pulled back some.
I'd only run 91-92 octane if your stock compression ratio was more than 10 (Like some of the later Imprezas) for the same reason stated above.
Don't take my word for it. Test the 87 octane vs 89 octane at a dragstrip sometime if you get a chance. Try to make sure the testing is in similar weather conditions (no more than 15 degress difference in temp). You'll see what I mean. Good luck!
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