89Cutlass Posted February 12, 2003 Report Share Posted February 12, 2003 I have an 89 olds cutlass supreme 2.8L someone told me i was supposed to run 93 in my car but it seems but car runs better with 89. What do you guys think ?? Quote Link to comment Share on other sites More sharing options...
NORBI Posted February 12, 2003 Report Share Posted February 12, 2003 Whoever told you that doesnt know anything about cars, those cars will run on 87 gas and even my 88 CS with 2.8 only runs on 87. When i put a better gas in it my gas milage suffers and i do about 20-30 miles less then i do on 87. Cars that need 93 gas are the ones with Turbo, Superchargers and those expensive luxury cars (Lexus, Mercedes). SO save money and put 87 in it. Quote Link to comment Share on other sites More sharing options...
MaD Posted February 12, 2003 Report Share Posted February 12, 2003 You're supposed to run the lowest octane that doesn't give you knock (which is usually 87). With your engine, it's built for 87, it's the turboed engines that require 92 or higher because it relies on the ehxaust gasses to work correctly. I put in 93 just because it seems to last longer than anything lower, and I really don't mind spending the extra $4 or so at the pump. Also, supposedly it burns cleaner than lower octane because it's full of detergents and shit...or whatever, but honestly, I think all grades are treated with the same detergents and the only difference is the actual octane rating. The only thing I've noticed is that my combustion chamber is a hair cleaner than when I used to run only regular or mid-grade. But yea, as long as your motor is in good condition, you can run regular with absolutely no problems. -MaD- Quote Link to comment Share on other sites More sharing options...
MaD Posted February 12, 2003 Report Share Posted February 12, 2003 whoops, sorry for reiterating, I guess you posted that as I was typing, NORBI. Damn, I haven't noticed a loss in mileage though from using 93. I should do a couple of tanks of regular to see if I'd gain any miles, what brand of gas do you use? I use Shell.. oh, and S/C'd engines need 92 also? I didn't know that...what's the reason why? -MaD- Quote Link to comment Share on other sites More sharing options...
luminator94 Posted February 12, 2003 Report Share Posted February 12, 2003 All my cars I run 87 except for the GTP. It requires 93, but I can sneak by sometimes with 89. I just run 87 in the other two because its a $1.68/gallon now for freakin' 87! Aaron Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 12, 2003 Report Share Posted February 12, 2003 my 3.1L doesnt like 87 at all. It idles a little rough and gets crappy MPG. I put in 89 and it idles a lot smoother and gets awesome MPG. The 87 makes my converterless exhaust pop a lot and lose low end torque. The 89 fixes all that. I dont know why, b/c these motors are made to run on 87. Any one have a clue?? Robby Quote Link to comment Share on other sites More sharing options...
TGPilot Posted February 12, 2003 Report Share Posted February 12, 2003 The higher the compression ratio...the higher the octane has to be. Normally aspirated cars normally run 8.5:1 compression or less and run best on 85-87 octane. Slightly higher compression motors 8.8:1 - 9.0:1 run on 89. Once you get up into the high performance and turbo/supercharged motors you will need 92 or better for the very high compression ratios. Some people think they are doing wonders for their cars by putting in higher octane and that it helps with performance in low compression motors. You are actually causing more polution in the air because un-burnt gas is running out your exhaust. Most likely if you don't have a "USE Premium Fuel Only" on your dash or in by your gas cap you can easily get away with 87 or lower octane. Most vehicles from the early 90's to today will trim the ignition timing to reduce the knock if lower octane gas is used. You will lose performance there for sure! Correct me if I am wrong anyone. Just the way it has been explained to me... 8) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 12, 2003 Report Share Posted February 12, 2003 Kenny, you said 92 is needed for turbo and s/c cars cause of the higher compression. I thought a turbo engine had lower compression? Correct me if I'm wrong. Quote Link to comment Share on other sites More sharing options...
MaD Posted February 12, 2003 Report Share Posted February 12, 2003 Worda, the compression on a n/a 3.1 is 8.9:1 and a turboed 3.1 is 8.8:1 I didn't know it had to do with compression, I just thought that the turbo used the unburnt gasses in the 92+ oct exhaust to spin the turbine better...or it makes it easier to produce boost...or something to that effect... -MaD- Quote Link to comment Share on other sites More sharing options...
90lumina3.1 Posted February 12, 2003 Report Share Posted February 12, 2003 they put lower compression then jam air in effectively raising the compression. Quote Link to comment Share on other sites More sharing options...
Whiskey River Posted February 12, 2003 Report Share Posted February 12, 2003 Here is a good website that explains the octane rating and what the most likely outcome will be. http://www.handymanusa.com/articles/octane.html Quote Link to comment Share on other sites More sharing options...
TGPilot Posted February 12, 2003 Report Share Posted February 12, 2003 Kenny, you said 92 is needed for turbo and s/c cars cause of the higher compression. I thought a turbo engine had lower compression? Correct me if I'm wrong. Yes, normally you need to lower the compression initially to run a turbo (to allow higher boost levels), but then when the turbo or supercharger compresses the air and then rams it down the cylinders throat, the density of the air and internal compression of the cylinder is much higher. That is most of the reason why you always hear us talking about knock in a motor with increased boost levels. Much more air (compressed and more dense than ambient air) will ignite the fuel much too fast. The lower the octane the easier it is to burn off. Higher the octane the harder it is to burn and that allows you to run a much higher compression. Higher compression = higher torque and HP. That is part of the reason why the MAP sensor needs to see proper pressure in the manifold so it can tell the ECM it is making boost and increase the fuel tables real quick! If you run lean at high levels of boost you will torch the motor... 8) Quote Link to comment Share on other sites More sharing options...
90TGP Posted February 12, 2003 Report Share Posted February 12, 2003 We're lucky out here in Ohio. I run Sunoco 94 or Shell 93. I also run octane booster every now and then. Quote Link to comment Share on other sites More sharing options...
TGPilot Posted February 12, 2003 Report Share Posted February 12, 2003 my 3.1L doesnt like 87 at all. It idles a little rough and gets crappy MPG. I put in 89 and it idles a lot smoother and gets awesome MPG. The 87 makes my converterless exhaust pop a lot and lose low end torque. The 89 fixes all that. I dont know why, b/c these motors are made to run on 87. Any one have a clue?? Robby If your motor pops when you are out of the throttle and are decelerating, it is normally a "lean pop". You could also have an exhaust manifold leak, but you say it runs rough and has no low end torque with 87 octane. If your 3.1 is running 8.9:1 and it is knocking, then most likely you have a serious amount of carbon build-up on your piston tops. With the carbon buildup you are actually increasing the compression ratio of the cyclinder because the cylinder size is decreased with the carbon build-up. I would suggest running BG fuel cleaner...it is expensive, but it works awesome. It does not allow the spark plugs or O2 sensor to get deposits on them like most alcohol based fuel cleaner additives. It will clean your exhaust valves and combustion chamber real well. NAPA carries all BG products. Hope this helps... 8) Quote Link to comment Share on other sites More sharing options...
89Cutlass Posted February 12, 2003 Author Report Share Posted February 12, 2003 can anyone with an owners manual for any vehical with a 2.8l MPFI motor veryfy what it says to use for octane ? Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted February 12, 2003 Report Share Posted February 12, 2003 Regardless of what anyone says, I run 91 Octane in my 2.8 Supreme...I have for over a year now and it just runs a lot better...it's a lot cleaner too... I've searched this topic to death on many GM and automotive forums and you'll NEVER get a straight answer that isn't contradicted by the very next poster...so I now just go by what feels better to me... Quote Link to comment Share on other sites More sharing options...
ismellrealbad Posted February 12, 2003 Report Share Posted February 12, 2003 well i think the best answer then, would be: This engine is deisgned for 87...but if you notice a positive difference with something else, then go with it. They also say use 5w-30 oil....i use either 10-30 or 10-40 with no probs. whatever works best and floats ur boat Quote Link to comment Share on other sites More sharing options...
BlueCutSupreme Posted February 13, 2003 Report Share Posted February 13, 2003 from my understanding, running other fuel types from what your car is designed for can throw off your timing. Any thoughts? Quote Link to comment Share on other sites More sharing options...
GnatGoSplat Posted February 13, 2003 Report Share Posted February 13, 2003 Yes, running lower octane than recommended by the manual will retard the timing. These engines have knock sensors and will prevent harmful engine knocking by retarding timing. The only harm to running higher-than recommended octane is to your wallet. http://www.quiktrip.com/gasoline/myth.asp I would personally never run higher octane than recommended by the manual. I'm too frugal to throw away money for no reason. If your car pings under load on a lower octane, you might benefit by using a higher octane. Both my truck and the 94 Cutty 3.4 DOHC ping on 87-octane under hard acceleration, but I'm too cheap to go up to 89 or 91 octane on them. Quote Link to comment Share on other sites More sharing options...
hambone Posted February 13, 2003 Report Share Posted February 13, 2003 i bought my '89 cutty new in '89. at that time they said the car would run on 87 but recommended at least 89. they did say that once selected to stick with it... as mentioned earlier use the octance rating that prvents knock/pings/run-on... i find that when i use 91 or higher i get better gas mileage. on the highway i usually get around 650 km per tank using 87-89 ( city is anywhere from high 400's to mid-500's ). if i use petrocan high test with the addtives that are in it i am getting 700-710. these are trips between upper canada and the east coast so roads are good ( double-highway to nb ) and flat. running through the hills of nb i will get high 600's i had a 2.8 but swapped out for a 3.1 when the timing chain broke... the bigger engine actually gives me better mileage! i figure it's 'cause the bigger engine isn't working as hard.... Quote Link to comment Share on other sites More sharing options...
godofthunder Posted February 13, 2003 Report Share Posted February 13, 2003 Ok, When my mom bought her 91 Lumina new, Chevrolet TOLD her to use premium name brand in the 3.1 I personaly use mid-grade. I have used premiuim at times, and notice I get about 30 more miles. So anyone know a deffianate answer? Debs truck it says rigth in the manual, Using anything OVER 87 Octane actually does NOTHING to the motor, and can actually harm perofmance Jon Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted February 13, 2003 Report Share Posted February 13, 2003 my 3.1L doesnt like 87 at all. It idles a little rough and gets crappy MPG. I put in 89 and it idles a lot smoother and gets awesome MPG. The 87 makes my converterless exhaust pop a lot and lose low end torque. The 89 fixes all that. I dont know why, b/c these motors are made to run on 87. Any one have a clue?? Robby If your motor pops when you are out of the throttle and are decelerating, it is normally a "lean pop". You could also have an exhaust manifold leak, but you say it runs rough and has no low end torque with 87 octane. If your 3.1 is running 8.9:1 and it is knocking, then most likely you have a serious amount of carbon build-up on your piston tops. With the carbon buildup you are actually increasing the compression ratio of the cyclinder because the cylinder size is decreased with the carbon build-up. I would suggest running BG fuel cleaner...it is expensive, but it works awesome. It does not allow the spark plugs or O2 sensor to get deposits on them like most alcohol based fuel cleaner additives. It will clean your exhaust valves and combustion chamber real well. NAPA carries all BG products. Hope this helps... 8) Its not a pop when I let off, its more of a rattle WHILE I am accelerating. I assume its b/c I got my exhaust done. Cuz before I had a straight pipe and it popped loud, b/c I had no backpressure. I put a turbo tube in and it cleaned the pop completely and gave me the low end torque I lost with no backpressure. I put the 87 in, and it doesnt idle real rough, but its smoother with 89. And, plus with 89 I get better MPG. I guess like Ismellrealbad said, whatever works best is best. Robby Quote Link to comment Share on other sites More sharing options...
no1kicker Posted February 13, 2003 Report Share Posted February 13, 2003 I usually run 89 in my STE, no one around here sells 91, just 93. I used to have a 91 Firebird with the 3.1 V6 and that ran on 87. However when I put 93 in it it had lots more power from the line. Quote Link to comment Share on other sites More sharing options...
CPSMonteZ34 Posted February 13, 2003 Report Share Posted February 13, 2003 Heat. If you didn't read the links above, the short version is basically that the higher the octane number, the slower-burning is the fuel. An engine designed for 91+ octane would pre-detonate with a lesser grade fuel...hurting the engine internals due to the fuel firing before the cylinder has reached it's moment when the timing would effectively fire the sparkplug when needed. Turbos, higher compression modifications, etc., all run hotter and can lead to pre-ignition of lower-grade fuels. Using a higher-grade octane fuel only means you are using a slower-burning fuel, effectively preventing pre-ignition until the timing of your electrical system distates when it's supposed to fire the charge in your cylinders. A good example would be a diesel engine. To get a big fire going in our field on Halloween, we tossed a near empty pail of diesel on it and it took a few minutes before the fuel would actually ignite. Diesel engines burn extremely hot, and it is a very slow burning fuel as a result. Put 87 octane in a diesel engine and you might as well be putting a grenade in there. This is why it has been said that putting a higher octane fuel in your engine can sometimes be bad due to the fact that you are not effectively burning all of the fuel when it sparks...meaning, some is heading straight out the exhaust pipe, and sometimes effecting power. Even worse, if your cat. converter is running hot, and you have fuel running through your exhaust pipes, you can wave that cat. goodbye. Quote Link to comment Share on other sites More sharing options...
NeonHomer Posted February 14, 2003 Report Share Posted February 14, 2003 My 88 w/ the 2.8 has 87 in it... My 85 Chrysler 5th Ave (318 v8, 2bbl) runs 87. My 87 Diplomat (318 4bbl), HAS to have 93, anything less and it rattles like hell! (Maybe it's also because I have 330,000 miles on the 87!!) Quote Link to comment Share on other sites More sharing options...
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