ean611 Posted June 23, 2008 Share Posted June 23, 2008 Ok, don't see a thread on this for NA engines, so here it goes. For the 2.5L Legacy engine, has anyone noticed a difference with premium? The engine has a 10:1 compression ratio, meaning that by my understanding, the knock sensor is what is saving my engine from regular fuel. Anyone find better MPG/HP or other effects by running premium? Link to comment Share on other sites More sharing options...
RaGe Posted June 23, 2008 Share Posted June 23, 2008 i didnt notice a damn thing when i had my 06 2.5i i ran both kinds and it ran about the same. Seemed as though i got less MPG with running premium. OTM. Sorry I didn't mean to start a war which mainly forum people is all about . Link to comment Share on other sites More sharing options...
pansontw Posted June 23, 2008 Share Posted June 23, 2008 I Ran Both On My 05 2.5i Wagon. For Premium, I Noticed Less Knocking And Smoother Acceleration Compared To Regular. However, I Do Get Better Mpg On Regular Gas. Maybe I Pushed Harder While Runnig Premium Gas. Link to comment Share on other sites More sharing options...
hutru01 Posted June 23, 2008 Share Posted June 23, 2008 Considering the difference in power or MPG can't be all that much due to the fact its N/A, you are much better off with regular (Save your money!) Link to comment Share on other sites More sharing options...
JayMitch2.5i Posted June 23, 2008 Share Posted June 23, 2008 You are wasting money using premium gas thinking thats its going to improve your performance. Premium has more detergents but is not going to help unless you have a high compression or Turbo engine. Link to comment Share on other sites More sharing options...
ean611 Posted June 23, 2008 Author Share Posted June 23, 2008 JayMitch2.5i, I ask the question, because 10:1 (NA Legacy Engine's compression ratio) is high enough to be considered high compression. Link to comment Share on other sites More sharing options...
dragonman586 Posted June 23, 2008 Share Posted June 23, 2008 The manual said use regular so thats what i do. Link to comment Share on other sites More sharing options...
Scrad Posted June 24, 2008 Share Posted June 24, 2008 When I had my NA I noticed that is got better MPG's with 87 compared to 89 or 93. Save your money and get the cheap stuff. Link to comment Share on other sites More sharing options...
808subaru Posted June 25, 2008 Share Posted June 25, 2008 JayMitch2.5i, I ask the question, because 10:1 (NA Legacy Engine's compression ratio) is high enough to be considered high compression. In my 3.0R, the required is regular unleaded (87oct). But I have tested it several fillups, and have seen a loss in MPG and power when using the cheap stuff. I don't know if having 2 extra cylinders and 1/2 L more than you guys makes a difference, but it's 92 only from now on for me. Link to comment Share on other sites More sharing options...
lfdal Posted June 25, 2008 Share Posted June 25, 2008 I thought the 3.0R's recommended premium but allowed you to run 87 octane with degraded performance? I understand the new Tribeca motor (3.?) H6 runs on 87 full time. Link to comment Share on other sites More sharing options...
Infamous1 Posted June 25, 2008 Share Posted June 25, 2008 I guess folks like to waste money around here.... Link to comment Share on other sites More sharing options...
iyalla Posted June 25, 2008 Share Posted June 25, 2008 I guess folks like to waste money around here.... I guess And no Premium does not have MORE detergents like someone mentioned above:rolleyes: Octane ratings simply measure the fuel's resistance to autoignition and the reason Premium gas cost more is that the components (alkylates) used to raise the octane level are expensive NOT the detergents. The detergents are the same at all octane levels. Here is an interesting fact....the price of premium is coming down relative to the price of Regular because less people are buying premium. The gas companies actually sell Premium at a cut rate so that it encourages people to buy it instead of dumping regular into their cars that require premium. If they were to sell premium at the same margins they are selling regular, premium would actually cost about 50 cents more Here are some car&driver articles for you to read http://www.caranddriver.com/reviews/hot_lists/high_performance/features_classic_cars/regular_or_premium_feature http://www.caranddriver.com/features/columns/c_d_staff/larry_webster/your_car_is_a_temple_so_put_in_the_good_stuff_column/(page)/1 Enjoy. Link to comment Share on other sites More sharing options...
ShadowImg Posted June 25, 2008 Share Posted June 25, 2008 When I had my NA I noticed that is got better MPG's with 87 compared to 89 or 93. Save your money and get the cheap stuff. Same here, I did quite a bit of testing in my 2.5RS between 87 and 89. 87 always felt like it gave better power, and I definitely saw better mileage on 87 than 89. I only tried 93 once, and it felt like I was driving on a tank of bad gas (which I suppose is possible). Link to comment Share on other sites More sharing options...
vet Posted June 25, 2008 Share Posted June 25, 2008 Doesn't 87 actually contain more energy than premium Link to comment Share on other sites More sharing options...
erikvcl Posted June 25, 2008 Share Posted June 25, 2008 Doesn't 87 actually contain more energy than premium No, premium has more energy, but 87 burns easier. HO NA engines (like say an F430; a stock NA 2.5i doesn't qualify as HO) and forced-induction engines need premium. For cars that don't need it, it'll be a waste of money. Link to comment Share on other sites More sharing options...
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