Now My Dad Thinks His STS Takes Regular Unleaded!!!

Chuck C · #1 (**permalink**) 03-08-03, 01:26 AM

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!

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!

Devil_concours · #2 (**permalink**) 03-08-03, 02:15 AM

in the new northstar engine, you are allowed to use regular gas unlike the older ones where it was required to use premium gas.

Chuck C · #3 (**permalink**) 03-08-03, 02:38 AM

!!! did not know that

rek · #4 (**permalink**) 03-08-03, 12:15 PM

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?

AKPsiMC03 · #5 (**permalink**) 03-08-03, 01:53 PM

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.

87CoupeDeVille · #6 (**permalink**) 03-08-03, 03:54 PM

The actual requirement for premium gas is now 92, gas stations can market it as premium as long as it meets that. I think 89 still needs to be 89.

Kurt

elwesso · #7 (**permalink**) 03-08-03, 04:59 PM

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.

rek · #8 (**permalink**) 03-08-03, 08:04 PM

http://www.mr2.com/TEXT/gasoline_faq.txt This place has one or two ideas about octane. http://www.gnttype.org/ this is where I got it. Explore the site, you'll find a good write up about home brew race gas mixture. Also, Rocket Fuel FAQ tells a tale about octane. Tech articles--- Misc.----Have fun!

Chuck C · #9 (**permalink**) 03-08-03, 11:14 PM

so is anything less than 89 octane bad for the new northstars?

BeelzeBob · #10 (**permalink**) 03-09-03, 01:42 AM

87 should even be fine.. The 2002 and newer Northstars run fine on 'regular' unleaded...

Chuck C · #11 (**permalink**) 03-09-03, 03:40 AM

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!

elwesso · #12 (**permalink**) 03-09-03, 10:04 AM

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

Devil_concours · #13 (**permalink**) 03-09-03, 10:54 AM

Quote:

Originally posted by Chuck C
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

elwesso · #14 (**permalink**) 03-09-03, 11:04 AM

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!

jadcock · #15 (**permalink**) 03-09-03, 11:04 AM

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.