Cadillac Owners Forum banner

1 - 20 of 28 Posts

·
Registered
Cadillac
Joined
·
28 Posts
Discussion Starter #1
Can it be used? Won't the computer adjust the timimg to compensate? If I did use it, it would be for around town driving. For highway I would switch back to premium. Or would the mpg in town drop significantly using midgrade?
 

·
Registered
1992 eldorado. 2007 dodge magnum hemi r/t
Joined
·
3,013 Posts
Can it be used? Won't the computer adjust the timimg to compensate? If I did use it, it would be for around town driving. For highway I would switch back to premium. Or would the mpg in town drop significantly using midgrade?

All I can tell you is that I use regular in my 97 sts and it runs fine.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
71,024 Posts
71, Go to the user CP up in the blue bar and update your profile with your car/model, year, mileage. It makes a difference because there were running changes to the ignition system, heads/cams, and block during the FWD Northstar production runs, all of which determine gasoline grade.

If your Fuel gauge or gas fill cover (?) say "Premium Fuel", then premium it is.

My '02 uses 87 very happily, and has no fuel mileage changes whether it gets 87 or 93.......and I drive the snot out of it.
 

·
Registered
2005 White Diamond STS N* 1SF RWD ACC/HUD
Joined
·
2,052 Posts
Yes, the Northstar has a knock sensor that will retard the timing if the sensor detects knocking from lower octane fuel. Many members here use regular in early model Northstars that were labeled "premium fuel only".
 

·
Registered
Cadillac
Joined
·
28 Posts
Discussion Starter #6
71, Go to the user CP up in the blue bar and update your profile with your car/model, year, mileage. It makes a difference because there were running changes to the ignition system, heads/cams, and block during the FWD Northstar production runs, all of which determine gasoline grade.

If your Fuel gauge or gas fill cover (?) say "Premium Fuel", then premium it is.

My '02 uses 87 very happily, and has no fuel mileage changes whether it gets 87 or 93.......and I drive the snot out of it.
It is a 1997 Eldorado.
 

·
Registered
'99 Eldorado 77,000 miles
Joined
·
291 Posts
I was using 87 for a while, but it sounded like my car was pinging. Moved back up to 89 and it seemed fine.

Which is fine by me because Iowa government subsidizes the ethanol stuff, making it cheaper than regular. I was only using regular when I was down in MO for school.
 

·
Super Moderator
2010 DTS
Joined
·
87,549 Posts
Can it be used?
Yes
Won't the computer adjust the timimg to compensate?
Yes
If I did use it, it would be for around town driving.
You can use it on the highway as well. Use premium if you are going to race it.
Or would the mpg in town drop significantly using midgrade?
I ran 87 in my '97 Deville and noticed no mileage or performance loss at all.
 

·
Registered
2007 EXT Supercharged
Joined
·
1,510 Posts
When i first got my N* i always ran premium. Got great milage with it.....up to 28MPG

Now i only use E10 with 89 octane. I only see 25-26MPG max or so, but premium is now 40 cents more a gallon and isnt worth it.

I think thats pretty good for E10
 

·
Registered
'08 DTS Lux III Blk Cherry, '89 Brougham d'Elegance Dip Blue
Joined
·
4,847 Posts
My 99 ETC says "premium only" on the fuel gauge. When gas was at it's highest around here I started running regular. Got the same mileage around town but not on the interstate. Regular will get me about 23mpg on the interstate, premium gets me 26+.
 

·
Registered
1992 eldorado. 2007 dodge magnum hemi r/t
Joined
·
3,013 Posts
I don't understand that. My '97 gave me 26+ on the highway all day long with 87.
I dont understand how premium fuel would give you more m.p.g., isn't the fuel "squirted" through injectors in the same amount,how would the computer know if it's prem. or reg?,just curious.
 

·
Super Moderator
2010 DTS
Joined
·
87,549 Posts
All the "computer" (PCM) knows is that it detects a spark knock (premium is more resistant to detonation). When it does, it retards the spark accordingly. That should no be a factor at cruise (highway driving).
 

·
Registered
not anymore 2007 Lexus ES350
Joined
·
7,705 Posts
When i first got my 2000 seville i thout that it was bad gas making it run the way it was when i twas the plenum that was bad
but i called the dealer and talked to one of the mechanics and service guys there they said the northstar i have is desined to run on 87 if i do ever hear a knock just switch up to 93 for a little whyll and it will be fine
i have only used 93 one time and that was after the first 6000 miles i had the car and only used it becosue i thout it might help to keep it clean if i ran one tank of 93 v power threw it
 

·
Registered
1997 ETC (GAVE TO STEPSON 2011), 2000 DTS (RIP)
Joined
·
1,702 Posts
I have a '97 ETC - bought it new off the showroom floor. I had always used Premium as per the gas cap, fuel gauge, and owners manual. Then I noticed that anytime I took it in for warranty work, I would get loaner and of course, fill it with regular (it's not my car, right?) and it would run just fine. In recent years, I think for pooping along around town, regular is fine. For highway trips, regular is fine. We drove cross country Boston to Phoenix 7 1/2 years ago on regular. I just drove round trip Phoenix to Las Vegas - about 600 miles total - 87 octane regular all the way - took it easy on speed - averaged 65-70 MPH - AC off - got 28.2 MPH - shocked myself. If you are driving around town, several people in the car, with the AC on, driving it hard with lots of stop and go, then Premium will yield a better result. When I did my HG project year and a half ago, I removed all of the combustion deposits from the combustion chamber, valve heads, and pistons - after that it seems it would run fine on just about anything
 

·
Registered
2007 EXT Supercharged
Joined
·
1,510 Posts
just remember that premium is not cleaner, does not clean better, or any other myths about better gas.

Premium is just a higher octane that allows more power if your vehicle is designed to burn it. If you have and old carbed 350 in stock form, premium will have no effect on milage or power.

Premium is usually said to get better in town milage in the N* motor. Its because the computer doesnt retard the timing as it does on lower grades.

Highway milage between premium and regular should be no difference, unless your climbing steep grades or the trans is downshifting alot.

If you want to clean your fuel system, start running E10, but at the same time change your fuel filter right after that tank as it will pickup all the crap and lodge it in your fitler.

If you going to shell or wherever, its not the premium that has additives or whatnot....its ALL of their grades.....premium has nothing to do with the cleaners or other additives that the gas station advertises.

Be careful though as some cars dont have knock sensors and can be damaged by running regular when they require premium. The 4.9 caddilac motor is one of them that require premium gas.

The premium is most beneficial in 100+ degree weaher and hard or WOT. If its -20F you probrably dont need premium in any motor.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
71,024 Posts
This is exactly the same thing we used to talk about on the dial telephone back in the 50's. Nothing's changed. We could get 103 at any pump in any station at any time for 32.9 cents. Sunoco used to sell 108 - as a matter of fact, you could blend just about anything you wanted, at the pump, from Sunoco.

If the engine is tuned for 93, run 93. If the engine is tuned for 87, run 87. If you're going to the strip in your 87 tuned car, run 93. If you're trailer towing in your 87, run 89. No brainer. Don't make it all more difficult than it really is.
 

·
Super Moderator
2010 DTS
Joined
·
87,549 Posts
When i first got my 2000 seville i thout that it was bad gas making it run the way it was when i twas the plenum that was bad
but i called the dealer and talked to one of the mechanics and service guys there they said the northstar i have is desined to run on 87 if i do ever hear a knock just switch up to 93 for a little whyll and it will be fine
i have only used 93 one time and that was after the first 6000 miles i had the car and only used it becosue i thout it might help to keep it clean if i ran one tank of 93 v power threw it
If the Shell marketing guys could read this they'd be patting themselves on the back and high 5ing. :highfive:
 
1 - 20 of 28 Posts
Top