yeshia Posted September 2, 2006 Author Share Posted September 2, 2006 I have been using 91 or above. I just was not sure if octane was very important, as I am a computer programmer, not a mechanic.... I kinda thought maybe that octance was just BS to get extra money out of me. I guess being as i does matter, I should use the 94. Thanks... didnt realize what a s*&t storm I was gonna create... Link to comment Share on other sites More sharing options...
cwmiller Posted September 2, 2006 Share Posted September 2, 2006 I can not even get 91 up here in Alaska. So no more whinning!! Dont want to hear it. The best we have is 90. I would be willing to pay good money for 93 or even 91 but no one has it. Link to comment Share on other sites More sharing options...
cwmiller Posted September 2, 2006 Share Posted September 2, 2006 If you run 89 oct your car will retard the timing and limit boost. Your gas mileage will suffer and so will a lot of power. The hotter the airtemp outside the more you will notice the effects. With the reduction in mileage and performance I don't think it is worth the $.10 per gallon savings. Will it kill your car?? No it wont the computer will compensate. Will you save money?? No, because you will loose mpg. The hotter the ambient air temp the more the you will notice the affect on your car. Link to comment Share on other sites More sharing options...
Moosedaddy Posted September 2, 2006 Share Posted September 2, 2006 My dealer told me I could put 89 in the car, but really for the difference of a couple hundred bucks a year, why bother risking any potential damage? Plus...it does run much better on the cleaner stuff. Link to comment Share on other sites More sharing options...
Vimy101 Posted September 2, 2006 Share Posted September 2, 2006 I can not even get 91 up here in Alaska. So no more whinning!! Dont want to hear it. The best we have is 90. I would be willing to pay good money for 93 or even 91 but no one has it. Cold air has the same effect as higher octane. It probably rarely gets hot enough for you to be concerned about knock. Link to comment Share on other sites More sharing options...
ShockerGT Posted September 2, 2006 Share Posted September 2, 2006 It's the $8000. tuneup that scares me. Otherwise if I had the $600k I'd be all over an Enzo. You'd only be buying half of an Enzo with 600k. They used to go for over 1.3mil new and used they are still going for 1mil. Anyhow, back on subject. If your car is FI, whether its blown, bottled or turbo'd, you should run 91+. Putting 87 in an LGT is like buying a $3000 HD DLP TV and just buying basic cable, sure you can watch the sports channels and perform basic function, but you're still not using the TV to its full potential. Link to comment Share on other sites More sharing options...
zmarko Posted September 3, 2006 Share Posted September 3, 2006 And besides, the price spread between regular and high grade has never been narrower thanks to the high price of gas now. Exactly! Now, back 8 or 9 years ago when gas was 99 cents a gallon, paying $1.19 was a 20% increase. Nowadays where gas is almost $3/gallon on a regular basis, an extra .20 a gallon doesn't seem that bad. Link to comment Share on other sites More sharing options...
G.T.Subie Posted September 3, 2006 Share Posted September 3, 2006 You can't even find 91 around here only 93. Spend the extra couple of $$$ Denial is your best friend Link to comment Share on other sites More sharing options...
Vimy101 Posted September 3, 2006 Share Posted September 3, 2006 You can't even find 91 around here only 93. Spend the extra couple of $$$ Please be aware that gasoline performance is standardized in N.A. The numbers on the pump are meaningless from region to region. What is important is the grade. Regions (soon to be all regions perhaps) that have up to 10% alcohol have higher "octane ratings" because alcohol does not want to ignite and contains less energy and therefore higher compression is necessary and this comes into play during hot weather. The pump R+M/2 is an anti knock index and doesn't refer to having any actual octane present at all. Link to comment Share on other sites More sharing options...
uroplatus Posted September 3, 2006 Share Posted September 3, 2006 ...mild pinging... is not a cumulative problem that kills an engine over time. Not quite true. It can indeed be cumulative, and it can damage an engine. Whether the effects will "kill" and engine could be debated, depending on one's definition of "kill an engine". Link to comment Share on other sites More sharing options...
uroplatus Posted September 3, 2006 Share Posted September 3, 2006 Don't forget about altitude. Up here at 6500', 87 octane performs just fine. There are lots of reasons why driving in higher altitude may require more octane (or higher anti-knock index gasoline). Link to comment Share on other sites More sharing options...
rporter Posted September 3, 2006 Share Posted September 3, 2006 Please be aware that gasoline performance is standardized in N.A. The numbers on the pump are meaningless from region to region. What is important is the grade. Regions (soon to be all regions perhaps) that have up to 10% alcohol have higher "octane ratings" because alcohol does not want to ignite and contains less energy and therefore higher compression is necessary and this comes into play during hot weather. The pump R+M/2 is an anti knock index and doesn't refer to having any actual octane present at all. ???? Anti-knock index = octane, and vice versa. 91 octane with 10 alky% in CA has the same antiknock capability as 91 octane straight gas in MI or NJ. The sole purpose of octane measurement is for the antiknock ability. Octane per se doesn't exist, it is a measurement. And it adds no pwer. I would rather see a BTU measurement. Folks will be surprised to learn that higher octane gas and/or oxygenated fuel (with alky), and with more additives, can have a lower BTU measurement. And BTUs give you the power and mileage, all else equal. Ron Link to comment Share on other sites More sharing options...
kmoney56 Posted September 3, 2006 Share Posted September 3, 2006 With your 2.5i it does. The GT running 87 would pull timing BAD. I always ran 93 in my Legacy, and 93 in the WRX now. (luckilly I have a station near my house that sells 93) Obviously never had a problem. Not with a turbo it wouldn't. Trust me. It would. I had a 91 300ZX TT and an 87 300ZX Turbo. Combined, I drove them for 3 years and almost strictly ran 87 or 89 and never once noticed any performance issues. Now, when I drove to see my family in Nebraska and dropped about 3-4000 ft and I had the wrong gas in the tank, I could absolutely tell the car was compensating for knock. At altitude, the turbo does keep the same pressure as at sea level (which is why they are so nice to have up here) but, although it's at the same pressure, it contains less oxygen so it's not as easy for the fuel to combust by compression. Link to comment Share on other sites More sharing options...
Vimy101 Posted September 4, 2006 Share Posted September 4, 2006 "Anti-knock index = octane, and vice versa. 91 octane with 10 alky% in CA has the same antiknock capability as 91 octane straight gas in MI or NJ. The sole purpose of octane measurement is for the antiknock ability. Octane per se doesn't exist, it is a measurement. And it adds no pwer." Precisely what I have been describing. However, BTUs as measurement is inadequate when desrcibing ICE fuel. Internal combustion engine fuel must have certain charateristics. In the olden days, autaul octane was used to lower flash points. Hence the modern confusion about anti knock indexes. At altitude there is less O2 density which decreases knock propensity. Link to comment Share on other sites More sharing options...
Vimy101 Posted September 4, 2006 Share Posted September 4, 2006 From Wikipedia: Octane is an alkane with the chemical formula C8H18. It has 18 isomers. One of the isomers, 2,2,4-trimethylpentane or isooctane, is of major importance, as it has been selected as the 100 point on the octane rating scale, with n-heptane as the zero point. Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance. It is an important constituent of gasoline. Link to comment Share on other sites More sharing options...
uroplatus Posted September 4, 2006 Share Posted September 4, 2006 At altitude there is less O2 density which decreases knock propensity. Lets not forget that some people who are driving at higher altitudes are driving up hill, with luggage, with a full load of people, and with the air conditioning on, because they're on vacation. That means the engine is experiencing greater loads, and will be more prone to detonation if the gas they are using doesn't support the octane requirements of the engine. Octane requirements for any particular engine can change over the life of the engine, due to carbon build-up on valves and pistons. For those folks reading this who are unsure of whether to use the lesser octane number gas, you should use the rating that your car mfr recommends, OR a higher octane rating. Link to comment Share on other sites More sharing options...
uroplatus Posted September 4, 2006 Share Posted September 4, 2006 Interesting discussion on the affect of different octane rated gas, from one of the Nissan/Infiniti web forums: http://forums2.freshalloy.com/showthread.php?t=155517 Link to comment Share on other sites More sharing options...
Vimy101 Posted September 4, 2006 Share Posted September 4, 2006 Interesting discussion on the affect of different octane rated gas, from one of the Nissan/Infiniti web forums: http://forums2.freshalloy.com/showthread.php?t=155517 I aquainted with that forum being a former J30t owner. One of the admins is a pal of mine from another Nissan site NICO. Regular burns hotter and, as we all know, heat is the enemy. Link to comment Share on other sites More sharing options...
uroplatus Posted September 4, 2006 Share Posted September 4, 2006 I aquainted with that forum being a former J30t owner. One of the admins is a pal of mine from another Nissan site NICO. Besides being a Subaru owner, I'm also an Infiniti owner, so thank you for the tip on the NICO site. I haven't seen that one before (http://www.nicoclub.com/); I've only been at FreshAlloy.com Link to comment Share on other sites More sharing options...
Vimy101 Posted September 4, 2006 Share Posted September 4, 2006 Besides being a Subaru owner, I'm also an Infiniti owner, so thank you for the tip on the NICO site. I haven't seen that one before (http://www.nicoclub.com/); I've only been at FreshAlloy.com I loved my J30t. Excellent car. What Infiniti do you have? NICO was an outgrowth of a Yahoo forum that went independent 4 or 5 years ago and was subsequently bought by another member. I learned a lot there. Check out a posts from member "Q45tech". I don't know if he's still active but what an amazingly complete understanding of automibiles he poccesses. Link to comment Share on other sites More sharing options...
rporter Posted September 4, 2006 Share Posted September 4, 2006 Interesting discussion on the affect of different octane rated gas, from one of the Nissan/Infiniti web forums: http://forums2.freshalloy.com/showthread.php?t=155517 As was mentioned there, a test sample of "one" is not very valid. And with a factory recommendation of 87 octane, to feel the engine needs 93 is not reasonable. 87 does not run "hotter". This is another thread, just like the one that appears here and on every other car forum, that attributes far too much importance to octane levels and what they think it does. Besides, strictly speaking, the higher the heat in the CC the better. Heat and expanded air is what pushes down the piston and makes the car move. Ron Link to comment Share on other sites More sharing options...
Vimy101 Posted September 4, 2006 Share Posted September 4, 2006 As was mentioned there, a test sample of "one" is not very valid. And with a factory recommendation of 87 octane, to feel the engine needs 93 is not reasonable. 87 does not run "hotter". This is another thread, just like the one that appears here and on every other car forum, that attributes far too much importance to octane levels and what they think it does. Besides, strictly speaking, the higher the heat in the CC the better. Heat and expanded air is what pushes down the piston and makes the car move. 87 does pre-ignite more easily which, as I understand it, would trigger the knock sensor retarding spark creating a lean condition that would increase temperature and that would be compensated by enriching the fuel mixture to create a cooler combustion temperature. There are many ways to skin a cat but I do know that Nissan engine design philosphy has been to build engines that run relatively rich in order to reduce cooling system requirements which reduces weight and parasitic power loss. However, I'm not an expert though I do play one on TV. Link to comment Share on other sites More sharing options...
uroplatus Posted September 4, 2006 Share Posted September 4, 2006 ...87 does not run "hotter".... ...strictly speaking, the higher the heat in the CC the better. Heat and expanded air is what pushes down the piston and makes the car move. Water injection is used to help prevent detonation. Isn't the purpose of the water injection to lower the temperture? Link to comment Share on other sites More sharing options...
uroplatus Posted September 4, 2006 Share Posted September 4, 2006 What Infiniti do you have? I have a 2004 FX35 and a 2006 M35x. Back in early '04, I went to look at a G35x, and drove home with an FX35. There were things I didn't like about the G, and the salesman let me take out an FX35 that had Nav and rear camera, etc, etc. I didn't know I needed those things until trying them out. The FX isn't light, but it does feel tossable and very composed and stable at near double the speed limit, even on curvy highways. Its been a good reliable vehicle so far. The M35x is a good mix of luxury and sport, with AWD. I was leaning toward a short wheelbase Audi A8, and then I heard about the new S8, and the fact that there would be a bunch of improvements for the A8 for model year '07 (such as rear camera, etc), so the '06 M35x was the next best thing (not to mention that it'll probably be a lot more reliable than the Audi product). To keep some Subaru content here, I have to comment that I wish Subaru had 1) a much more loaded (sport and luxury) Legacy GT/STi/Spec.B (or whatever else they want to call it), OR 2) the rumored "executive sedan", that is a little larger than the Legacy (such as Audi A8 short wheelbase size or Infiniti M35/45 size), with all the goodies of an A8/S8 or loaded Infiniti M. Years ago, I used to search for coins under my seats, just to afford gas to go out for an evening. Eventually I got older, and had some success, and now I can afford to buy more expensive cars, and the price of gas is not a worry for me anymore; but Subaru hasn't grown with me. I'd really rather buy a Subaru product, but Subaru doesn't have what I'm looking for. I have not seen the '07 Spec.B Legacy yet. Who knows, maybe I'll like it, but based on the features list, its missing some things. I'll compare it to the new '07 Infiniti G35 when thats available in Nov'06. I want to replace my old Subaru Legacy GT, so it could be a Spec.B, or maybe the new G35. Or maybe a Corvette... Link to comment Share on other sites More sharing options...
rporter Posted September 4, 2006 Share Posted September 4, 2006 Water injection is used to help prevent detonation. Isn't the purpose of the water injection to lower the temperture? It's used to prevent heat at the wrong time.....as in too early or too late in the combustion process. Ron Link to comment Share on other sites More sharing options...
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