Alex GL-10 Posted March 23, 2006 Share Posted March 23, 2006 Why do some people say that using premium in a turbo suby is better, and others say regular is? What do people on here use? I konw it depends on how moded a engine is. My EA82T is complety stock and my owners manual says to use 87. I use the cheapest I can find. Never below 87. I've also heard 87 in the U.S. is like 91 in other countries. If that is true i'm all ready using almost premium. Quote Link to comment Share on other sites More sharing options...
calebz Posted March 23, 2006 Share Posted March 23, 2006 93 only for me. The loss of power and increased chance of detonation aren't worth the few bucks a week difference in price. Quote Link to comment Share on other sites More sharing options...
Tom63050 Posted March 23, 2006 Share Posted March 23, 2006 Why do some people say that using premium in a turbo suby is better, and others say regular is? What do people on here use? I konw it depends on how moded a engine is. My EA82T is complety stock and my owners manual says to use 87. I use the cheapest I can find. Never below 87. I've also heard 87 in the U.S. is like 91 in other countries. If that is true i'm all ready using almost premium. 87 is fine for normal use for non-turbo cars; I don't know about turbos. If ignition timing is advanced beyond stock, higher octane helps prevent detonation. That's all it really does; cars that require 93 octane just have more-advanced ignition timing. Higher octane does not actually directly give more horsepower. Quote Link to comment Share on other sites More sharing options...
Gl-boost Posted March 23, 2006 Share Posted March 23, 2006 I have run 87 in my turbo, it was ok but ideld alittle funny and is not as peppy when I run 93 oct. I have used 89 also and that seemed fine. Quote Link to comment Share on other sites More sharing options...
75subie Posted March 23, 2006 Share Posted March 23, 2006 i think that theory is a bunch of balogna but thats me. my uncle runs 87 in both his 2000 vett and 2000 benz kompressor super charged. he has never noticed a power decrease, and the milage stayed the same. with the amount he drives, it saves him alot by using regular grade gas. Quote Link to comment Share on other sites More sharing options...
Gl-boost Posted March 23, 2006 Share Posted March 23, 2006 yea, I don't think it really maters ither, I guess I just think it is faster because you think of this when you run high octane gas. Quote Link to comment Share on other sites More sharing options...
rllywgn Posted March 23, 2006 Share Posted March 23, 2006 most manufacturers recommend 92 or higher octane fuel for turbocharged vehicles. the increased octane combats detonation better in turbo cars. you increase the chance of knock under full boost. i dont wanna blow my motor, i know running premium is gonna help that little bit.. every little bit helps right also.. if your the type that keeps the weight on the go pedal and the boost at full steam you may want to run only 92 or higher rllywgn Quote Link to comment Share on other sites More sharing options...
mbrickell Posted March 23, 2006 Share Posted March 23, 2006 Well, in theory, since higher octane means the fuel does not burn as easily, if you had no or a poor intercooler, and the temperature of the intake charge was high, I would say that higher octane gas would be of benefit. The more risk of detonation, the greater the need for higher octane. My other initial impression is that modern cars from the last few years with very sophisticated engine management may be able to compensate much better for lower octane fuel than older more primitive systems. I would imagine that the older your car, the more benefit being conservative and running higher octane fuel would be. On a "primitive" turbo car, I would err on the side of running higher grade fuel. Less of an electronic safety net should you need it. On a recent car, you won't notice things going haywire due to low grade fuel as the electronics will compensate and back off timing advance, boost, or other factors to save expensive parts from damage. The driver would not notice or would only notice a little performance loss. This would explain why someone with a relatively new high performance car may have run lesser fuel and not noticed any difference, although much may be actually occurring to adjust. For a non-turbo car, I would say that 90% of the time at least, premium is a waste of your money unless you are running high compression or have some cylinder head temp issues of some sort... Quote Link to comment Share on other sites More sharing options...
jeffast Posted March 23, 2006 Share Posted March 23, 2006 have an n/a and i have to run 91(premium here) or it detonates but my timing is at like thirty degree's vrs the stock 22 Quote Link to comment Share on other sites More sharing options...
mbrickell Posted March 23, 2006 Share Posted March 23, 2006 have an n/a and i have to run 91(premium here) or it detonates but my timing is at like thirty degree's vrs the stock 22 would seem to make sense. hyper-advanced timing would mean octane more critical i would think. thinking more about it, considering that a car from the late 80's or early to mid 1990s probably has about 1000 times less computing power than a new car today, the sensitivity of an old turbo car to fuel octane is probably orders of magnitude greater than a new car. around here, you can get midgrade at 89 or 90, i would at least run that. the 96 volvo 850 turbo wagon my wife had said 90 or better now that i think about it... Quote Link to comment Share on other sites More sharing options...
calebz Posted March 23, 2006 Share Posted March 23, 2006 yea, I don't think it really maters ither, I guess I just think it is faster because you think of this when you run high octane gas. You would actually be wrong in thinking that. Even our old fuel systems make timing adjustments on the fly to compensate for various environmental variables. I'll make this as simple as possible. On the back of your block, you have a knock sensor. When your car detonates, or pings (most commonly due to crappy fuel), the knock sensor picks that up. What does it do with that info? It sends a voltage signal to the ECU. The ECU then retards timing to help compensate for the noise. What happens when the timing is in a constant state of retardation? You lose power. This is not a theory boys and girls. This is a basic fact of forced induction cars. It is tangible and measurable. This is where it can get a little tricky. Our old cars are not terribly intelligent.. They can only pull so much timing, and on top of that there are very few other ways that they have to compensate for less than ideal running conditions (read again: crappy fuel). Once it reaches its limit of how much timing can be pulled, you are basically stuck. *shrug* if its worth a few bucks a week savings, have at it. Over a decade of forced induction cars has shown me it is not worth it to run crappy fuel. Quote Link to comment Share on other sites More sharing options...
nkx Posted March 23, 2006 Share Posted March 23, 2006 87 will get you by in a pinch if you baby a turbo car. keep your foot in it, and expect knock and maybe some broken rods or pistons. Quote Link to comment Share on other sites More sharing options...
mikeshoup Posted March 23, 2006 Share Posted March 23, 2006 My XT Turbo is running SPFI pistons... Nothing but premium for her. I'd hate to imagine what anything lower would do to her. I would say, you'd be fine with regular. Just listen for nocking, and pay attention to any stumbling / hesitation from the car. Quote Link to comment Share on other sites More sharing options...
rallyruss Posted March 23, 2006 Share Posted March 23, 2006 I have been forced to run 87 before and have noticed a drop in performance and evin a bit of pinging under hard load(hill climbs) Caleb has laid our exactly how it works. thats all fact. not "my uncle joe bob says he can run 87 octain and still make 600 hp with his ford topaz" with a normaly aspirated car you can usually get away with 87 no problem. espically in cold weather. the real use of high octain fuel is for forced induction and high compression cars. now if you dared to put those two together you better be running higher octain. Quote Link to comment Share on other sites More sharing options...
Alex GL-10 Posted March 23, 2006 Author Share Posted March 23, 2006 87 will get you by in a pinch if you baby a turbo car. keep your foot in it, and expect knock and maybe some broken rods or pistons. I don't exactly baby my car. Its not like I have a 40 gallon tank like my moms van it wouldn't be much more. Quote Link to comment Share on other sites More sharing options...
Mr Fishums Posted March 23, 2006 Share Posted March 23, 2006 When I ran higher octane fuel in my old camaro, It got better mileage on the highway. It was a non turbo small block chevy. High octane fuel is better for power and preformance, if your motor can handle it. When I fill up my subaru, I go with premium 92 octane.... because if you do the math it's only about $1.50 more a tank. I've spent more on beef jerky. PEace, Fishums Quote Link to comment Share on other sites More sharing options...
soobscript Posted March 23, 2006 Share Posted March 23, 2006 My experience: 88 RX turbo With stock 200k-mile engine, unknown timing (it ran fine when I bought it), and blown headgasket(s) - regular 87 octane was fine. After complete longblock overhaul and Delta Cams - 93 octane. Noticeable power loss with regular gas. Just after getting it running, before I got the timing right I would get MAJOR knock (read: brick wall) at WOT aver 3500 rpms on 87 and 89. It never did "pinging" it was more like fuel cut, tach just stopped moving. After fixing the timing back to about 22*, the brick wall knock stopped, but it definitely felt sluggish compared to 93 octane. Interesting note from a dealer sales brochure for the 1987.5 models: all HP tests were done with 91 octane. That could be Japanese 91 though, which would be equivalent to US 87. Quote Link to comment Share on other sites More sharing options...
tizzle Posted March 23, 2006 Share Posted March 23, 2006 My RX seems to run better on plus grade Quote Link to comment Share on other sites More sharing options...
Durania Posted March 24, 2006 Share Posted March 24, 2006 I believe that it is STRONGLY recommended that you run high octane fuel in a vehicle that has anything that aids to aspiration (turbocharger/supercharger). My aunt has a super-charged Grand Prix and she accidentally but regular in it and it through the ECU all out of wack, they had to drain the gas tank cause it made it run like garbage. Quote Link to comment Share on other sites More sharing options...
NoahDL88 Posted March 24, 2006 Share Posted March 24, 2006 High octane fuel is better for power and preformance, if your motor can handle it. It is only better if you detonate on regular, or if you are running a power adder, as it has been previously stated. On a stock Non-turbo, anything higher than 87 is a waste of money, unless the owners manual calls for more octane. The higher the octane the longer the hydrocarbon chain, and the harder it is for the spark plug to ignite the fuel air mixture. Octane's only function is to resist detonation, which high compression and turbo motors take advantage of. As per my "Automotive Engines, Theory and Servicing" by Halderman and Ellinger, as part of my Automotive Engineering Technology degree "Do not purchase fuel with a higher-octane rating than is necessary. Try using premium high octane fuel to check for operating differences. Most newer engines are equipped with a detonation (knock) sensor that signals the vehicle computer to retard the ignition timing when spark knock occurs. Therefore, an operationg difference may not be noticeable to the driver when using a low-octane fuel, except for a decrease in power and fuel economy. In other words, the engine with a knock sensor the engine will tend to operate knock free on regular fuel even if premium is specified. Using premium fuel may result in more power and fuel economy. The increase in fuel economy , however, whould have to be substantial to justify the increased cost of high-octane fuel. Some drivers find a good compromise by using midgrade fuel to benifit from engine power and fuel economy gains without the cost of using premium all the time." Cliff notes: If your manual says use 87, you'd better, or Mr T is gonna come to your house and pitty you, and then Chuck Norris will roundhouse kick you just to drive the point home. But if your manual says to use 92, you probably should, unless your car is 96 and newer, then it will be alright to use 87, but it will be down on power. Quote Link to comment Share on other sites More sharing options...
dxrflyboy Posted March 24, 2006 Share Posted March 24, 2006 I believe that it is STRONGLY recommended that you run high octane fuel in a vehicle that has anything that aids to aspiration (turbocharger/supercharger). My aunt has a super-charged Grand Prix and she accidentally but regular in it and it through the ECU all out of wack, they had to drain the gas tank cause it made it run like garbage. Why not dump some octane booster in it before you go through all that trouble? Or was it a case of being taken for a LONG ride through her wallet? Quote Link to comment Share on other sites More sharing options...
Durania Posted March 24, 2006 Share Posted March 24, 2006 Why not dump some octane booster in it before you go through all that trouble? Or was it a case of being taken for a LONG ride through her wallet? Well thats the thing, my aunt before taking time to think just simply drove it straight to the mechanic. I am convinced that she could've put that fellar through college by all the work she has had done on that GM garbage. Quote Link to comment Share on other sites More sharing options...
Dylan86GL10 Posted March 24, 2006 Share Posted March 24, 2006 i think that theory is a bunch of balogna but thats me. my uncle runs 87 in both his 2000 vett and 2000 benz kompressor super charged. he has never noticed a power decrease, and the milage stayed the same. with the amount he drives, it saves him alot by using regular grade gas. Both of those cars have a sophisticated knock feedback circuit. Doesn't really compare to a EA82 at all. On my 85 Shelby Charger (turbo) I gained more mpg by using 93 than I lost by the extra money. Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted March 24, 2006 Share Posted March 24, 2006 Some time Ago, I readed a Full Article about the Low and High Octane Fuels... It`s All About Detonation, since low Octane detonates more.... But it can be traduced in More Power, Let me Explain: The main coil of the Regular EA82 is of 27,000 Volts Output, but this isn`t enough power to combat the detonation due to misfires, so, if You put in a more powerfull Coil (I got the Accel SuperStock Solid Coil -Off Road Use- that delivers over 45,000 Volts) and do "Clean" from carbon deposits your engine (Those that make Dieseling in Weberized Subies) You`ll have More Power from the overtimed engine. But just a Little Overtiming. about 20º. How to Clean Carbon Deposits in your Engine? There are many chemical things that claim to do that, but the easier is this: when the engine gets it`s normal operating Temp. Just open the Air filter Box, and with the Engine revving about @ 2,500 RPM`s, let drop right on the Carb a Small Amount of Clean Water, ( one or two onces ) You`ll notice a "Blackened" exhaust smoke coming from behind the car... Repeat this untill the "Blackened" fumes gone... And that`s it! Good Luck! Quote Link to comment Share on other sites More sharing options...
Mr Fishums Posted March 27, 2006 Share Posted March 27, 2006 Are the octane ratings on AV and race gas different? Because I have a more than noticable power gain when I run these. Quote Link to comment Share on other sites More sharing options...
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