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My dad has been putting regular gas in his car per advice of the salesperson! My bro is borrowing it at the moment, so I couldn't show him the "premium unleaded only" decals and owner's manual. I have a feeling that even if he sees that it says premium, he'll still put in regular (esp. since it's leased and gas $$ is sky high). I also tried to tell him that it says Premium Unleaded Only right in front of my face in my car! :banghead:


Help me to convince my dad that the salesperson was wrong and that his 2003 STS needs premium unleaded only. Also tell him why high Octane is so important in order for the Northstar to sustain a long life!
 

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Chuck, I think the higher output NS in the STS still requires Premium fuel....A Caddy sales rep told me that, but I haven't checked for sure. The price difference between 93 octane and the next lower grade is a dime a gallon here. SO, 20 gallons, is two bucks difference. No big deal. It's a CADILLAC . It will run on lower octane, but the spark timing will be changed, and less power will be made. Why buy a race horse, then feed him less then he needs? Premium has a slower burn rate. Some would argue that you will get better milage with premium, in a vehicle designed for it. Bottom line, use what the Factory says to use, they know a bit about their product. I have read that some gas, sold as 93 octane, is actually lower than 93. If they do that, how low would gas sold as 89 octane actually be?
 

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they lowered the compression on the the 02+ northstar which alows you to run regular. it used ot be 10.3:1 (i think) now its down to 10.0:1... so regular is good... all they did was reshap the combustion chamber on the heads.
 

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What i do with my Q, i alternate every other tank. If i can remember, i put half of premium in it, and when it gets to half i top it off with mid grade. The octane requirement is 91.

Personally, i would put in premium. It will run so much smoother, and will get better gas mileage.
 

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They will run fine, but they will run better on premium.
 

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Chuck C said:
okay, good, that's what we filled it with today. BTW, I drove it for the first time today, and mannnn, what a great ride. Lincoln Continental (previous car)...a joke compared the STS!
all around performance(handling, accleration, braking, cornering) should be at another level than lincoln. Have fun and drive safely
 

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I do like the air suspension on the continentals. It keeps the rear level, and it feels like your riding on air, because you are! The only thing those are good for is highway cruising, and its not so good if your in the back seat!
 

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You can run regular gas in any Northstar. L37 vs. LD8 makes no difference. Up to 1995 (I think it was 1995), they all said premium REQUIRED. After 1995, they changed it to RECOMMENDED because of increased gasoline prices. The engines still run fine on regular gasoline. The engine is equipped with a spark retardation system in the event of spark knock. Since the engine was designed from the beginning to run premium gasoline, you'll get the best performance out of premium gasoline. If you run less than premium, you may get some spark knock; the spark timing would then be retarded and the knock will go away, at the expense of a few horsepower.

Starting in 2000, the engines were redesigned. The combusion chambers are completely different. The compression ratio is now down to 10:1 (versus 10.3:1 for the earlier heads). Cadillac recommends regular gas in 2000+ cars. Since the engine and computer system are now designed with regular gas in mind, there is no reason to run any higher octane, since there should be no spark knock with regular gas, and thus, no performance compromises with that gas.
 

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Fuel Grade Shell Game. Take a look at www.fueleconomy.gov for listing of the manufacturer's reported fuel grades for each model. Site is run by Department of Energy. You should also be able to view a hardcopy pamphlet at the dealership but it does not list all models. For example, the 2003 pamphlet shows Deville as using regular gas. So, GM is telling the Feds that regular gas is the design fuel, even when many can't get by on anything but premium or regular plus booster plus carbon cleaner. That's even if we use best source regular and travel hours at 70+ every week.

So, how can our reality differ so much from what the manufacturer certifies to the government?
 

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Hi Chuck,
Does your father's STS have the Variable Valve Timing? There are a lot of advantages to the VVT. One of them is lower octane gas, another is more power, and a third is greater efficiciency.
Jon
 

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rapid rabbit said:
My 2000 Esc uses regular. The fuel gauge decal calls for premium, but I was told to ignore it. It runs great.
My dad was stupid and did that too, and then I noticed the engine knocking around 40 mph! Before I took delivery of the car I MADE him put in the PREMIUM that is REQUIRED for that engine! I was concerned there would be engine damage, as well as deformed sparkplug electrodes, there wasn't, thank God! He is hard of hearing and could not hear the knocking. Cadillacs are so well insulated for noise control, that you may very well NOT BE ABLE TO HEAR THE ENGINE DAMAGE OCCURING, so please, do yourself a favor and put in PREMIUM. I may as well just saved you thousands in repairs. Learn from other people's stupid mistakes.
 
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