: Northstar using unleaded fuel?



Caddy Man
05-16-04, 05:08 PM
whats up people...ive heard the the generation of Northstar that came in the 2000 DTS and up caddys were engineered to run perfectly fine and with all 300 hp on regular (87 octane) gasoline. I've always been relutcant of this though and have always bought premium, but with the gas prices now, i am contemplating on using regular if i kno there is gonna be no damage and the car works fine. Can anyone tell me any details about this so i am more clear on it? thanks!

Chuck C
05-16-04, 05:13 PM
My understanding is that the latest gen Northstars have a lower compression ratio than Northstars of past generations thus reducing the recommended octane rating to 87. I assure you that there will be no damage if you use 87.

El Dobro
05-17-04, 12:54 AM
It should tell you right in the owners manual that regular is fine for 2000 and up. If the factory say it's ok then go ahead and use it.

Ralph
05-17-04, 02:16 AM
Yup, the 2003 manual says it's ok to run premium. I heard the same for 2000. Now if only my 1991 could. :rant2:

Caddy Man
05-17-04, 08:54 AM
coo thanks guys!

Smokey
05-17-04, 10:58 AM
It's my understanding that the 2000+ N* still have about a 10:1 compression ratio, but they have a system that will control the spark timing and will retard the timing to prevent detonation when using regular unleaded. My 1998 Lincoln Continental had the same setup. It ran fine on regular, just did not have as much "snap" to the performance when running the lower octane fuel.

BeelzeBob
05-17-04, 11:36 PM
It's my understanding that the 2000+ N* still have about a 10:1 compression ratio, but they have a system that will control the spark timing and will retard the timing to prevent detonation when using regular unleaded. My 1998 Lincoln Continental had the same setup. It ran fine on regular, just did not have as much "snap" to the performance when running the lower octane fuel.

Misunderstanding here.....

All Northstars have a very sophisticated knock control system that will protect the engine against detonation or spark knock. That is on all of them from the very beginning in 93.

What you say is actually more true of the 93-99 Northstars. They are designed and tuned for maximum output on premium fuel but will run fine on regular .... just with a slight loss of performance and fuel economy under certain conditions when the knock control system has to pull a lot of spark advance out of the system to protect the engine. The engine will not be damaged at all and it will run fine on regular.

The 2000 and later Northstars were completely redesigned and optimized for operation on regular fuel. The compression ratio of the 2000 and later engines is .3 lower (it went from 10.3:1 to 10:1) and the combustion chamber of the 2000 and later engines is redesigned to promote faster burn and more knock resistence. The 2000 and later engines will make the same power as the earlier Northstars but they do not require premium to do it. They will run fine on regular. That is the recommended fuel in the owners manual..... The 2000 and later engines have the same knock control system to protect the engine in the event of substandard fuel or certain conditions that might cause it to knock on the regular fuel and it will protect the engine in this case with little or no feedback to the driver.

Smokey
05-18-04, 11:09 AM
So running my 2000 Deville on regular unleaded is okay? No performance loss as with my 1998 Continental? Is there any advantage to running premium fuel in the 2000+ N*? Once again, thanks for your valuable info and patience.

kevinK
05-18-04, 12:33 PM
Misunderstanding here.....

All Northstars have a very sophisticated knock control system that will protect the engine against detonation or spark knock. That is on all of them from the very beginning in 93.

What you say is actually more true of the 93-99 Northstars. They are designed and tuned for maximum output on premium fuel but will run fine on regular .... just with a slight loss of performance and fuel economy under certain conditions when the knock control system has to pull a lot of spark advance out of the system to protect the engine. The engine will not be damaged at all and it will run fine on regular.

The 2000 and later Northstars were completely redesigned and optimized for operation on regular fuel. The compression ratio of the 2000 and later engines is .3 lower (it went from 10.3:1 to 10:1) and the combustion chamber of the 2000 and later engines is redesigned to promote faster burn and more knock resistence. The 2000 and later engines will make the same power as the earlier Northstars but they do not require premium to do it. They will run fine on regular. That is the recommended fuel in the owners manual..... The 2000 and later engines have the same knock control system to protect the engine in the event of substandard fuel or certain conditions that might cause it to knock on the regular fuel and it will protect the engine in this case with little or no feedback to the driver.

My 98 Deville will knock on accelaration when I use 87 octane feel. I am not sure that 1993 to 1999 Northstar vehicle can use regular gas.

BeelzeBob
05-18-04, 02:17 PM
Let me repeat....the 2000 and later Northstar are designed and tuned to run on regular.....that means that you can run them on regular will little or no concern for power loss or loss of fuel economy.


I am SURE that it is OK to run a 93-99 Northstar on regular. If you doubt this, check the owners manual for the 97 and later Northstar engines...the fuel requirement went from premium "required" to premium "recommended" and the "premium required" nomenclature was removed from the dash and the fuel filler cap (except for the Eldo....the nomenclature stayed on the dash to avoid retooling the dash cluster....regular is fine, though).


A 93-99 Northstar is designed and tuned for premium fuel. Running mid-grade or regular fuel will likely result in some spark retard from the knock control sytem and under extreme conditions (hot/dry, very very cold) there may be some transient spark knock evident. That will not hurt anything but there is just too much spark retard required to prevent all the detonation under the extreme conditions.

The fuel recommendations always allow for producing maximum power under all (including worst case conditions). If the knock control has to retard the spark then it will not make maximum power... The worst case for detonation is hot/dry ambient or very very cold/dry ambients. In these cases the 93-99 engines need premium. If you are going to tow a trailer thru Death Valley in the summer with a 93-99 then use premium. For back and forth the work in the spring and fall in Michigan....regular will likely work fine with little or no spark retard and no detonation or driveability issues. I usually say that the 93-99 Northstar is "happy" 40-50 percent of the time on regular and the rest of teh time requires mid or premium to make the ultimate power.

The 2000 and later Northstars are "happy" 80-85 % of the time on regular. They will still like mid or premium under worst case conditions to make max power. If you are towing that trailer thru Death Valley with your 2000 or later I would still recommend premium for max power and the least amount of spark retard as the engine runs warmer. If you are going to the track for a day or racing your buddy put premium in to assure best power if the coolant temp comes up. Otherwise regular is fine.

Caddy Man
05-18-04, 06:25 PM
Misunderstanding here.....

All Northstars have a very sophisticated knock control system that will protect the engine against detonation or spark knock. That is on all of them from the very beginning in 93.

What you say is actually more true of the 93-99 Northstars. They are designed and tuned for maximum output on premium fuel but will run fine on regular .... just with a slight loss of performance and fuel economy under certain conditions when the knock control system has to pull a lot of spark advance out of the system to protect the engine. The engine will not be damaged at all and it will run fine on regular.

The 2000 and later Northstars were completely redesigned and optimized for operation on regular fuel. The compression ratio of the 2000 and later engines is .3 lower (it went from 10.3:1 to 10:1) and the combustion chamber of the 2000 and later engines is redesigned to promote faster burn and more knock resistence. The 2000 and later engines will make the same power as the earlier Northstars but they do not require premium to do it. They will run fine on regular. That is the recommended fuel in the owners manual..... The 2000 and later engines have the same knock control system to protect the engine in the event of substandard fuel or certain conditions that might cause it to knock on the regular fuel and it will protect the engine in this case with little or no feedback to the driver.
great this is exactly what i was lookin for. thanks!

Smokey
05-18-04, 07:06 PM
I apologize if I seemed dense, but with current gas prices, I was just trying to determine if I could save some money. The reason I asked was the following excerpt from my 2000 Deville owner's manual page #6-3:
"Use premium unleaded gasoline rated at 91 octane or higher for best performance. You may use middle grade or regular unleaded gasolines, but your vehicle's acceleration may be slightly reduced."

Stoneage_Caddy
05-18-04, 08:17 PM
"Now if only my 1991 could. "

hang in there ralph , we will all find out mondy when mine runs on 87 and 3 deg ret timing in 92f degree weather

Ralph
05-18-04, 08:26 PM
"Now if only my 1991 could. "

hang in there ralph , we will all find out mondy when mine runs on 87 and 3 deg ret timing in 92f degree weather

I might try mid-grade if this keeps up!

Just don't blow 'er up eh! :tisk:

David Schlichting
05-18-04, 09:53 PM
I've used Mobil gas in my 2000 SLS from the time it was new. There was always some knock using regular so have used the mid grade. Maybe it is something with the formulation here on Long Island, as I have had no problem with Mobil Regular in Connecticut (formulated with ethanol) I have not tried regular since New York eliminated the MTBE (?) from gas a while back

OlManRivah
05-18-04, 10:10 PM
I apologize if I seemed dense, but with current gas prices, I was just trying to determine if I could save some money. The reason I asked was the following excerpt from my 2000 Deville owner's manual page #6-3:
"Use premium unleaded gasoline rated at 91 octane or higher for best performance. You may use middle grade or regular unleaded gasolines, but your vehicle's acceleration may be slightly reduced."
Not true with my 1997. It states in the manual to be sure the posted octane for premium is at least 91. Only use lower octane in an emergency--as low as 87-- if heavy knocking does not occur.

I assume this is also for 93 thru 99. I'll stick with the high octane in mine, no matter what the price. I'm not going to gamble my Eldo to save $3.00 on a fill up.:tisk:

Smokey
05-18-04, 10:20 PM
At the local gas prices, it cost .10 a gallon to go with premium over regular. After doing some math, I would only save about $15.00 every 3000 miles. Nah, I'll just stick with the premium stuff to be sure. :) Call me old fashion I guess. I know the Caddy ran better than it did when I bought it after about the 2nd tank full of premium. I have never put anything but premium in it since. I know one thing, it DOES make a difference in a '98 Continental. :)

El Dobro
05-18-04, 11:09 PM
On the Allante, when you go into diagnostics, PCM Data #PD42 tells you the calculated octane level of the fuel. The next time I fill up, I'll give it a shot to see if it works. I guess it tells from the knock sensor function.