TDK Posted June 16, 2004 Report Share Posted June 16, 2004 I believe Premium has some additives that retard combustion - to allow it to explode a tad slower (which is still darn fast at any rpm). per Encarta: Explosives, chemical compounds or mixtures that undergo rapid burning or decomposition with the generation of large amounts of gas and heat and the consequent production of sudden pressure effects. This retarding "spreads the explosion out", (if you can envison spreading out those milli-seconds) instead of one quick bang - hence engine knock. I suppose the engine can be retarded or you buy the retarded fuel (that didn't read quite so well). <_< I could not say if these additives leave any residue in cylinder, intake (not much with FI anyway) or exhaust. I'm sure there is a more technical reason for the differance in octane and I'm also sure extra processing relates to higher prices. It might be interesting to know the differance in the various octane production costs and how that differance is "marketed" (read: jacked up prices). I run 87 in town where there isn't much "challange" and no priorty for mileage. On a trip I'll feed it some 91 or 93 "desert", but make it work for it. Heck, I've even shutdown the AC, if it needs everything its got... for a few moments. Ain't broke anything for maybe 4-years...yet. Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 Go ahead and run your Northstar with 87 octane and see how long it lasts... I don't know how long you have been on this site but do a few searches in the archives. Look for fuel, octane, knock, knock sensors etc. Pay particular attention to posts from Bbobynski (a GM powertrain engineer). I don't know what your credentials are but if you dispute what he has been saying I for one would really appreciate hearing it. I seriously doubt burning 87 octane will bring about an early demise to my Northstar. Link to comment Share on other sites More sharing options...
JasonA Posted June 16, 2004 Report Share Posted June 16, 2004 The Northstar shouldn't knock on 92 octane. There might be a problem with the knock sensor. I agree. There aren't any codes, and a while ago, it was suggested that I pull the intake and verify that the knock sensor is plugged in, tight in the block, etc, which I did, to no avail. I haven't replaced the sensor yet. But I think it's interesting that there are no knock sensor codes...if the sensor really is bad. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
pagesix1536 Posted June 16, 2004 Report Share Posted June 16, 2004 I seriously doubt burning 87 octane will bring about an early demise to my Northstar. It's your choice I suppose. If the manufacturer suggests premium fuel, and you choose not to use it because it "costs too much". That's up to you. 10.3:1 is not extremely high compression, but it's not low either. I'm not disputing that the Northstar can't run on 87, I'm sure it can and the engine/computers will attempt to adjust for this (probably at the cost of lower performance because of timing adjustments the engine has to make to compensate). But why chance it anyways. If you can afford to buy a Cadillac, you can probably afford the premium fuel too. Link to comment Share on other sites More sharing options...
Chris Posted June 16, 2004 Report Share Posted June 16, 2004 Chris, how are you seeing the timing retard in the OBD? I've never found that on my '97, but would be very interested to have that display, since mine knocks even on 92 octane under heavy throttle. With the car running, enter OBD as if you were checking for codes. After any codes have been displayed, it shows 'PCM?'. Press fan speed up for 'yes'. Press fan speed down for 'no' until you get to 'PCM Displays' or something like that. Use up and down to cycle through the displays. You will get to one 'PD40'. Just drive around. It displays knock sensor spark retard in degrees. See the entire list of displays at the bottom of this page: http://myweb.accessus.net/~090/dtcobd1.html -Chris Link to comment Share on other sites More sharing options...
Regis Posted June 16, 2004 Report Share Posted June 16, 2004 When we were kids, my brother had this cactus plant. One day he thought he would put the left-over bottom swill from dad's daily beer can/bottle to "good" use by feeding it to the cactus. His justification was that the beer was mostly water and it should work. Mom (green thumb) thought about it and said he was theoretically correct but knew better and so let him try his experiment. The cactus, after awhile, turned a funky shade of yellow but lived for a year and then went off to cactus heaven. Commom sense dictates to me that unless GM and fuel manufacturers are owned by the same company and there is a huge conspiracy to defraud the public on octane usage and that there is a general assumption that the public as well as the countless lawyers are mindless bafoons that don't take car manual recommendations seriously..... then I should probably use what's "recommended". But this is the land of the free and free choice and i think it's a good thing that we have test pilots for the "cactus experiment". "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
JasonA Posted June 16, 2004 Report Share Posted June 16, 2004 It's your choice I suppose. If the manufacturer suggests premium fuel, and you choose not to use it because it "costs too much". That's up to you. 10.3:1 is not extremely high compression, but it's not low either. I'm not disputing that the Northstar can't run on 87, I'm sure it can and the engine/computers will attempt to adjust for this (probably at the cost of lower performance because of timing adjustments the engine has to make to compensate). But why chance it anyways. The reasoning would be to not use premium because it's not necessary. That's the same reason I don't use synthetic oil. If it was required, I'd use it, but it's not, so I choose not to spend the extra money on it. Same deal with the gasoline. In reality, you might loose maybe 5hp running 87 octane. Usually, you'll loose less than that. The general recommendation was made "requiring" 92 octane to cover all cars, in all situations, in all cases, to get the most performance, whether you're in Florida in the dead of summer or Minnesota in the dead of winter. 99% can run 87 all the time with no problems, and no real decrease in performance. But there are some situations where there will be some spark retard if you're running anything less than premium, so the recommendation was made to always use it to extract the most performance out of the engine under all circumstances. Here's a snippet from our "resident engineer": The 93/99 Northstar engine is designed and optimized to operate on premium fuel. The compression ratio and the spark advance programmed into the PCM are optimized to make the most power and best economy on premium fuel. Lesser grades of fuel will result in detonation in some conditions. If this happens, the knock control system will detect the detonation with the knock sensor and retard the spark advance to prevent the detonation. This results in slightly less power and slightly less fuel economy. Generally speaking, though, it is fairly transparent to the operator that the knock control is having to do anything. What does it mean to you??? You can run most any grade or octane rating of fuel in a Northstar without worrying about engine damage or anything. You might notice some slight degradation in power/economy/driveablity on hot/dry days or very cold/dry days. If you do, then use a higher octane fuel. If you absolutely want to gurantee the best power/economy under all conditions then run premium. If you try regular and can't tell the difference then feel free to use it. The Northstar engine was redesigned for the 2000 model year and will run happily on regular fuel most all the time. Same as the above applies as it has a knock control system to protect the engine. If you have a 4.9 engine, the situation is about the same...but...there is no knock control system to protect the engine. The engine is optimized for premium fuel and if a lower grade of fuel is used some spark knock may be encountered/heard. If so, use better fuel. If no knock is heard, then continue using the lower grade of fuel. The "official" fuel requirements for the engines ..i.e...premium fuel...are stated that way so that under ALL conditions the engine will provide the best power and fuel economy. If I can fix mine (maybe it's a knock sensor), I'd probably run 87 as well. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
Norton1 Posted June 16, 2004 Report Share Posted June 16, 2004 Let's see - I started using the el-cheapo fuel in my 94 STS a while back. Almost 10,000 miles later my mileage has improved and my fuel costs are significantly reduced. I was getting 22-23 mpg and now have recorded, coming through Colorado a week or so a go, 30 mpg. Average mpg for the 2000+ mile trip was above 27 mpg. I had my wife and her mother with me as well as all of our baggage for the trip of 5 days. We did 1000 miles the first day and I'm a lead foot for the most part. I'll take a GM engineer's word for how the motor works over about anyone elses. As a former drag racer I understand the concept and the execution of how the 4.6 Northstar works. You are not going to hurt it with cheaper fuel. If I was going to race it I'd put the premium in it for the extra couple of horses - but I have noticed no performance decrease. And I drive this car a lot. And fuel around here is $2.05 for the cheap regulat 87 octane stuff - try $2.25 for premium at the el-cheapo stations! And octane is about combustability. Do a search on it and you'll find the reality of how it effects performance. Just my experience - Steve Link to comment Share on other sites More sharing options...
JasonA Posted June 17, 2004 Report Share Posted June 17, 2004 Please stand corrected. Premium fuel is not "dirtier"..... In fact, especially in the past, the best cleaners and detergents were in the premium fuel additive packages so it would be more correct to say that it burns cleaner due to the detergent package. Thanks for the correction. Maybe I shouldn't have used the word "dirtier". I've heard somewhere that premium fuel, strictly compared to regular, will leave more deposits when burned than regular, due to the extra additives that are added to it. Kind of like sludge from VI in historical 10W-40 oil but obviously a different issue. Again, I forgot where I read that, and maybe it's all horse-puckey. Can you comment on more or fewer deposits left by premium fuel? Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
ByStorm Posted June 17, 2004 Report Share Posted June 17, 2004 So am I wasting my money by using premium gas in my '01 STS? My car seems to be running excellent since the day I purchased it. ByStorm Link to comment Share on other sites More sharing options...
ByStorm Posted June 17, 2004 Report Share Posted June 17, 2004 Thanks B.... ByStorm Link to comment Share on other sites More sharing options...
WarrenJ1 Posted June 17, 2004 Report Share Posted June 17, 2004 Once again, Guru, thanks for the wealth of information. Gosh, I hope you touch type . . . . I'd hate to think we take so much of your time. Regards, Warren P.S. I remarked once before that I enjoyed your avatar. Is there some special significance regarding the numeral "6"? EDIT: Edited for spelling . . . . probably missed something anyway . . . Link to comment Share on other sites More sharing options...
JasonA Posted June 17, 2004 Report Share Posted June 17, 2004 At another point in the late 80's the detergents changed and intake valve deposits became a real issue as the intake deposit formation caused drivablitliy problems on many port fuel injected engines due to the deposits acting like a "sponge" on the intake and causing hesitations when accelerating. A lot has been learned on this and the learning continues.... I'm sure what I heard or read was an old shadetree mechanic's wives tale, maybe based on the situation you described above. Again, many thanks for your knowledge and time! Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
ByStorm Posted June 17, 2004 Report Share Posted June 17, 2004 BBobynski, (or anyone else) You said something about staying with a better brand of gas, what would be considered a better brand I currently use Hess gasoline. And how does the consumer determine this besides price? ByStorm Link to comment Share on other sites More sharing options...
JasonA Posted June 19, 2004 Report Share Posted June 19, 2004 I just got back from a business trip down to Savannah, GA. On the way, along a rural South Carolina highway, I passed a service station named...and I kid you not...El Cheapo. I didn't gas up there...not even the rented Taurus I was driving. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.