timokon@yahoo.com Posted June 15, 2004 Report Share Posted June 15, 2004 I have been told by mechanics that it no longer matters what fuel Octane you use, as today's computer controlled engines make constant allownces and adjustments according to what's going into the combustion chamber. I have also been told that Higher Octanf fuel is cleaner, and WILL make a difference in the overall life of the engine. ANy thoughts? Tim Link to comment Share on other sites More sharing options...
KHE Posted June 15, 2004 Report Share Posted June 15, 2004 Your 4.9 engine does not have a knock sensor. If you use too low of octane, the engine will exhibit spark knock which is bad for the engine. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
JasonA Posted June 15, 2004 Report Share Posted June 15, 2004 In fact, higher octane fuel tends to burn "dirtier", meaning it tends to leave more deposits in the engine. I forget where I read that. Someone please correct me as necessary. 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...
Scotty Posted June 15, 2004 Report Share Posted June 15, 2004 Then I have a question, my 96 Deville has Premium gas only on the dash and I have been using premium (Ouch these days). Is that OK or will the middle grade suffice during the cooler months? Mike Link to comment Share on other sites More sharing options...
rek Posted June 15, 2004 Report Share Posted June 15, 2004 I use premium in all my cars. They all "call" for it. For some reason, my 20 HP, 6 speed, tanning bed (garden tractor) gets more MPMPT (Mowed Plant Material Per Tank) with premium fuel, than if I use low octane in it. Regular lasts about 150 minutes of cut time. Premium lasts about 14 minutes longer. Go figure, it calls for regular. One time I was out of Mowing gas and dumped some "Race Gas" (The good lacquer/glue smelling stuff) in it. Hey, it mowed longer and smelled better. Next I tried pump premium. Vola, longer run time. I think the Premium burns slower... rek Link to comment Share on other sites More sharing options...
KHE Posted June 15, 2004 Report Share Posted June 15, 2004 Then I have a question, my 96 Deville has Premium gas only on the dash and I have been using premium (Ouch these days). Is that OK or will the middle grade suffice during the cooler months? Mike You will be fine running premium. I run regular in my '96 SLS and have not noticed any performance or mileage loss....even so, it only saves $3.50 per fillup. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Scotty Posted June 15, 2004 Report Share Posted June 15, 2004 Then I have a question, my 96 Deville has Premium gas only on the dash and I have been using premium (Ouch these days). Is that OK or will the middle grade suffice during the cooler months? Mike You will be fine running premium. I run regular in my '96 SLS and have not noticed any performance or mileage loss....even so, it only saves $3.50 per fillup. Kevin can I run the middle grade successfully? Mike Link to comment Share on other sites More sharing options...
GOOB Posted June 15, 2004 Report Share Posted June 15, 2004 Kevin can I run the middle grade successfully? Mike i've been running 89 (middle grade) for the past month and have not noticed a difference (yet) Link to comment Share on other sites More sharing options...
KHE Posted June 15, 2004 Report Share Posted June 15, 2004 Then I have a question, my 96 Deville has Premium gas only on the dash and I have been using premium (Ouch these days). Is that OK or will the middle grade suffice during the cooler months? Mike You will be fine running premium. I run regular in my '96 SLS and have not noticed any performance or mileage loss....even so, it only saves $3.50 per fillup. Kevin can I run the middle grade successfully? Mike Sure - the Northstar will retard the timing if spark knock is detected. You may notice a slight performance and mileage loss - I didn't in my '96. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
dankhts Posted June 15, 2004 Report Share Posted June 15, 2004 On a Caddy STS, you'll see in the owners manual, that anything prior to 2000 model year, REQUIRES premium gas, 91 octane minimum. On the 2000 and newer, the owner's manual says premium fuel RECOMMENDED. There's a diferrence between recommended and required. Using 87 octane on a '99 or older, may result in damage to the spark plugs and/or wires. There would be little diferrence noticable in performance however. On the 2000 and newer, the manual even states that you will get bettere performance with premium gas than regular. Hence the "recommended" part vs he "required" part. My '96 ran about 2 months on regular gas before needing a spark plug change, compared to 100,000 plus miles on premium before needing plugs. Link to comment Share on other sites More sharing options...
Scotty Posted June 15, 2004 Report Share Posted June 15, 2004 On a Caddy STS, you'll see in the owners manual, that anything prior to 2000 model year, REQUIRES premium gas, 91 octane minimum. On the 2000 and newer, the owner's manual says premium fuel RECOMMENDED. There's a diferrence between recommended and required. Using 87 octane on a '99 or older, may result in damage to the spark plugs and/or wires. There would be little diferrence noticable in performance however. On the 2000 and newer, the manual even states that you will get bettere performance with premium gas than regular. Hence the "recommended" part vs he "required" part. My '96 ran about 2 months on regular gas before needing a spark plug change, compared to 100,000 plus miles on premium before needing plugs. You raise a good point, i have been using 93 octane.. I am going to check my manual and see if I can do with 91 octane till this gas mess is over, Thanks, Mike Link to comment Share on other sites More sharing options...
PAUL T Posted June 15, 2004 Report Share Posted June 15, 2004 I use Premium in my 92 Deville(4.9) and the 94 Concours(4.6). When I used regular gas in them I did notice a slight differance in performance and about 2 to 3 MPG less. I stick with premium. Link to comment Share on other sites More sharing options...
KHE Posted June 15, 2004 Report Share Posted June 15, 2004 On a Caddy STS, you'll see in the owners manual, that anything prior to 2000 model year, REQUIRES premium gas, 91 octane minimum. On the 2000 and newer, the owner's manual says premium fuel RECOMMENDED. There's a diferrence between recommended and required. Using 87 octane on a '99 or older, may result in damage to the spark plugs and/or wires. There would be little diferrence noticable in performance however. On the 2000 and newer, the manual even states that you will get bettere performance with premium gas than regular. Hence the "recommended" part vs he "required" part. My '96 ran about 2 months on regular gas before needing a spark plug change, compared to 100,000 plus miles on premium before needing plugs. You won't damage the Northstar's plug wires or plugs by running 87 octane in a pre-2000 Northstar. If spark knock is detected, the ECM retards the timing. That's where a loss of performance/mileage will occur. I have been using 87 octane in my '96 for four years and cannot perceive any loss of performance or fuel economy. If you notice a substantial loss of fuel ecomomy, switch back to premium. The 4.9 engine does not have a knock sensor and will spark knock if too low of octane fuel is used. You must manually retard the timing a few degrees on a 4.9 in order to run regular. Then, the resulting lower fuel economy will probably offset the savings at the pump.... Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
CadiKing Posted June 15, 2004 Report Share Posted June 15, 2004 ....till this gas mess is over, Thanks, Mike Hey Mike, Sounds like you may think this gas mess will be ending soon? I've been waiting for it to end since it started in 1972(?). Floor it while you can still Afford to... my .02 Link to comment Share on other sites More sharing options...
Chris Posted June 15, 2004 Report Share Posted June 15, 2004 I run 87 in my '93 no problems. If you go into OBD and goto the timing retardation, I notice that the 87 octane only 'tries to knock' during WOT accels. In these cases, the spark is just retarded a tad. I havent noticed any worse gas mileage. -Chris Link to comment Share on other sites More sharing options...
Marika Posted June 15, 2004 Report Share Posted June 15, 2004 Premium will actually give you better gas mileage for the $$$. In my 92 Seville with the 4.9L, I tried to use the midrange "silver" and found that it knocked slightly under heavier loads, such as when I was going up hills. I also noticed a decrease in gas mileage and since I'm now paying $2.05 for a gallon of premium, I stick with the premium. (and yes, my fuel pump is still fine, Scotty et al). If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
Regis Posted June 16, 2004 Report Share Posted June 16, 2004 Mike, I think KHE said it correctly. You only end up saving around $3.50 per fill up (more or less). These gas discussions always seem to end the same. I look at it this way: You're driving around in a darn fine American made piece of machinary ....the boys in Detroit seem to think it's important to run at least 91 octane ....and someone tells you different ....hmmm who should i listen to ....if saving the extra latte' money is important enough to fabricate a justification for using cheaper gas then perhaps some of these caddys should be traded in for a hybrid, geo metro,or a Yugo. But Mike you drive a caddy! Be proud and suck it up, deny your wife that latte and put that money to better use. -kg 206,000 premium gas miles "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...
Marika Posted June 16, 2004 Report Share Posted June 16, 2004 ...traded in for a hybrid, geo metro,or a Yugo. You know, this reminds me of the time I managed to actually fit inside a Yugo. The problems started when I tried to then bring my radar detector into it as well.......LOLOLOLOL!!!!!!!! If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans. Link to comment Share on other sites More sharing options...
JasonA Posted June 16, 2004 Report Share Posted June 16, 2004 I run 87 in my '93 no problems. If you go into OBD and goto the timing retardation, I notice that the 87 octane only 'tries to knock' during WOT accels. In these cases, the spark is just retarded a tad. 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. 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...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 I used to burn 92 and switched to 87 on the advice of Guru (the boys in detroit). I have noticed NO difference in performance, even under WOT. Maybe at the track being timed I might. If your gonna race it burn 92. The great Northstar will detect spark knock and retard the timing appropriately. As far as MPG, I think I noticed the slightest increase, maybe .5-.8 MPG but could not swear to it. Save your money an burn 87. Johnny G is in the petroleum buisness and I think it was he who once posted about 87 burning cleaner and giving better MPG. I'm sure he & Guru will jump in here. Link to comment Share on other sites More sharing options...
KHE Posted June 16, 2004 Report Share Posted June 16, 2004 ...since mine knocks even on 92 octane under heavy throttle. Jason, The Northstar shouldn't knock on 92 octane. There might be a problem with the knock sensor. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Ranger Posted June 16, 2004 Report Share Posted June 16, 2004 ...since mine knocks even on 92 octane under heavy throttle. Jason, The Northstar shouldn't knock on 92 octane. There might be a problem with the knock sensor. The Northstar shouldn't knock on 87 much less 92. There is a definate problem. How many knock sensors does the Northstar have? Link to comment Share on other sites More sharing options...
KHE Posted June 16, 2004 Report Share Posted June 16, 2004 I think only one and it is mounted under the intake manifold. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
pagesix1536 Posted June 16, 2004 Report Share Posted June 16, 2004 amusing....knock sensor or not, on a high compression engine, without higher octane fuel.....the fuel ignites before it's supposed to (before the spark) on the upstroke of a cylinder (the compression stroke). The sheer amount of compression is enough to combust low octane fuel spontaneously. The Northstar 4.6 is a high compression engine. The minor tweaks in later years of these engines to allow lower octane come at the price of lower performance because of highly adjusted timing on the engine (all computer controlled of course). I have a Neon with 12.5:1 compression pistons, and you better believe pump gas is a no-no in this sort of setup. Go ahead and run your Northstar with 87 octane and see how long it lasts... Link to comment Share on other sites More sharing options...
Scotty Posted June 16, 2004 Report Share Posted June 16, 2004 Well its not necessarily the idea of saving money for me at all. As a matter of fact I probably use the most expensive gas in the area and never use off brand gas. It is more about, if I can get away with 91, why should I continue to use 93? I do tend to overkill when I don't have to. And yes I do spend a fortune at Starbucks, but hey thats high octane also. What really made me begin to think were the statements about the higher octanes not burning as clean and here I am using 93 all the time. I must say one thing however, since I have eliminated my AC Compressor she is really peppy. It really surprises me how much power I have since eliminated the compressor.. Then again maybe is just in my mind as the whinning is gone, and the engine just pulls now with negligible noise, maybe I had gotten so used to the noise that it masked how the car actually felt, who knows. I find it hard to believe that the AC compressor was dragging me down that much, unless the bearing was so bad that it put a strain on the engine. Thanks for the discussion, nite all, Mike Link to comment Share on other sites More sharing options...
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