: What Octane gas is best?



uiwchris
03-09-07, 04:39 PM
I must have gotten a bad batch of gas. At stoplights the car chokes then recovers. I have had problems with his particular brand of gas before in a Pontiac Grand Prix.

I was wondering what octane is best to use? I have been putting in 89. Here in the midwest, most stations carry 87-89-91. I was wondering if I should start putting in 91 in the future (and a different brand obviously).

Anyone else have their car choke at stop lights?

Thanks

STS2002
03-09-07, 04:46 PM
Well, you have the V8. And it is recommended that you use premium (91 octane) with this engine.

Caroutisine
03-09-07, 07:48 PM
You have the V8.
I have always used premium in my STS V8 from several sources and never had a problem...between 91 and 93 octane.

malcolm
03-09-07, 08:13 PM
I started out at 91 and even fell for V-Power 93 from Shell for a time in my V8. One day I was low and the Exxon station I pulled into only had regular. I took a tank full and never looked back. The car runs exactly the way it did on high octane, same mileage, idles so smooth I sometimes can't tell it's running. I know nobody drives these cars to save money but with the price of gas these days but it adds up. Not to mention all my previous Northstars recommended regular.

Jesda
03-09-07, 10:02 PM
It only seems to run fine because the sensors detect detonation and retard the timing. This means DETONATION HAS ALREADY OCCURRED. THIS IS BAD. Use 91+ and nothing else on a RWD Northstar. 2000+ FWD Northstars specify regular due to a lower compression ratio. They are NOT the exact same engine.

Also, when you factor in tank and transport contamination, that 91 sometimes gets diluted down to 90. Going for 92-93 can't hurt.

Also, as gas prices rise, upgrading premium only gets CHEAPER! The difference of 20% back when regular was $1.00 is now only 5-15%.

caddi2005sts
03-10-07, 10:00 AM
I had a 2000 sts, got in 2002 and just got a 2005 (dec) and have only put in 87, call me cheap - but i have had no problems at all . I have put 91 and 93 in during the cold months and gas antifreeze. NO PROBLEMS AT ALL.....

malcolm
03-10-07, 08:01 PM
I don't want to get into a big thing here but what does front or rear wheel drive have to do with compression of the engine? My 02 Seville 300HP specified 87. My 05 STS 325HP wants 91. Sorry I am not drinking that cool aid for a 25HP difference.

Caroutisine
03-11-07, 07:40 PM
It's amazing that some folks don't want to spend an extra buck or 2 on a fillup, then others don't trust the oil life monitor and waste money on synthetic oil changes at 3K miles. I would just follow the instructions for fuel and maintenance that came with the car. :)

malcolm
03-11-07, 10:22 PM
It's amazing that some folks think the difference is a buck or two on a fillup and believe everything they read in the owners manual. Check the price of gas and assuming your father is not buying your gas, the difference can be somewhere between 50 and 100 dollars a month. That cash looks pretty good in my pocket every month.

Caroutisine
03-11-07, 11:58 PM
Yea...guess they should do the same thing they did back in the mid '70's when the switch was made from regular to unleaded gas. Make the nozzle at the pump a diffenent size to force people to put the right gas in their car. Even if it costs a few pennies more.:bigroll:

Amazing to me that people complain about a premium gas requirement in a $50K car. Even if you didn't pay that much, it's still an expensive car. Maintenance is expensive, insurance is expensive, repairs are expensive...it's an expensive car.

I gave my daughter a 2004 Monte Carlo Supercharged for her graduation (much less than $50K) and she complains about having to put the "expensive" gas in it...but I can kind of see the point from someone who is 19 years old and paying for their own gas.

If anyone is spending $50 - $100 a month just to put premium in a V8 STS, you're driving it a lot. Assuming this, you would have to fill up every day of the week. ($3 per tank x 7 days a week x 4 weeks per month = $84 per month) I'm jelous, wish I put this kind of windshield time on my STS. If looking for economy, the STS V8 is the wrong choice regardless of the fuel.

Back in 1975, if you busted out the filler tube on your gas tank you could fill up on the less expensive "leaded" regular...and the car would run just fine too. Today we don't have that problem, just push the 87 button and you're all set. Put whatever you want in it, it's your car. Personally, I'll spend less than $150 PER YEAR for the premium.

BTW the owners manual was written by the company that made the car. I doubt that GM is getting a kick back from anyone for recommending 91 octaine in the STS V8. More likely, the enginge was designed to use high octaine fuel. And they just may have more than a clue about its operation; outside of what it takes to just make it go down the road.

Aurora5000
03-12-07, 09:10 AM
Use regular gas at fillup and add "Seafoam" in gas every oil change.


http://www.seafoamsales.com/motorTuneUpTechGas.htm

Jesda
03-12-07, 10:51 AM
I don't want to get into a big thing here but what does front or rear wheel drive have to do with compression of the engine? My 02 Seville 300HP specified 87. My 05 STS 325HP wants 91. Sorry I am not drinking that cool aid for a 25HP difference.

The Northstar went through a few changes when it was revised for the new RWD Cadillacs. Its not the exact same engine as the lower-compression one that preceded it in the 2000+ Seville and Deville.

STS2002
03-12-07, 10:00 PM
Here's how I see it......

We can put whatever gas we want in our cars. It will still go! However, like Jesda says, these are high compression engines now and Cadillac recommends the use of premium gas to achieve maximum performance (unless you bought the V6, which use of regular is fine). We knew this when we bought this $55,000+ car. And then what happens a year down the road and you start to have mechanical issues with the engine and it ends up being a result of detenation/engine knocking and we all then start to complain because the car has to be in service for a bad engine (possible out of pocket expenses because it won't be covered under warrenty) and we blame GM/Cadillac. When they were the one's to print in the owners manual that premium is strongly recommended and the use of regular could cause damage to the engine. Again.....each of us can use whatever octane we want....just be prepared if damage occurs. And seriously, I don't mean to be a pain, but if we can afford payments ranging from 600-800, we should be able to afford the premium gas to put in it. Just my opinions here! :-)

corvette00
03-13-07, 08:18 AM
I am on my second v8 Sigma based STS. I have not put premium in the 05 or the 07 and the vehicles have performed just fine. I supposed if I owned the vehicle instead of leasing I may change my mind. However, if you go on the Cadillac web site and look under DTS specifications, then click Powertrain and look under "fuel recommended" it states "premium unleaded". Perform the same search on the STS and it does not recommend a fuel grade, perhaps this is due to the V6.

Cajonkev
03-13-07, 02:05 PM
With a modern, computer moderated engine that can/will easily mask any symptoms until damage is far along I personaly have decided to error on the side of caution and run nothing but 91 octane fuel from a "Top Tier" providor through mine.

That said, I certainly respect that folks will do whatever they feel most comfortable with and we all make decisions based on our knowledge, experience, environment and upbringing.

So in the spirit of good discussion and debate while dealing from a basis of fact, here is the actual paragraph(s) as listed in the 06 & 05 manuals (I do not have the 07). The recommendations are slightly different than some previous posts and so I list them for clarification towards a healthy debate/discussion...:rant2:

I'll just sit over here and watch...:alchi:

2006 STS/STS-V Manual:

Gasoline Octane
If your vehicle has the 3.6L V6 engine (VIN Code 7),
use regular unleaded gasoline with a posted octane
rating of 87 or higher. For best performance or trailer
towing, you may choose to use middle grade 89 octane
unleaded gasoline. If the octane rating is less than
87, you may notice an audible knocking noise when you
drive, commonly referred to as spark knock. If this
occurs, use a gasoline rated at 87 octane or higher as
soon as possible. If you are using gasoline rated at
87 octane or higher and you hear heavy knocking, your
engine needs service.
If your vehicle has the 4.6L V8 engine (VIN Code A),
use premium unleaded gasoline with a posted octane
rating of 91 or higher. You may also use regular
unleaded gasoline rated at 87 octane or higher, but
your vehicle’s acceleration may be slightly reduced, and
you may notice a slight audible knocking noise,
commonly referred to as spark knock. If the octane is
less than 87, you may notice a heavy knocking
noise when you drive. If this occurs, use a gasoline
rated at 87 octane or higher as soon as possible.
Otherwise, you might damage your engine. If you are
using gasoline rated at 87 octane or higher and you hear
heavy knocking, your engine needs service.
If your vehicle has the 4.4L V8 engine (VIN Code D),
use premium unleaded gasoline with a posted
octane rating of 91 or higher. For best performance, use
premium unleaded gasoline with a posted octane
rating of 93. In an emergency, you can use regular
unleaded gasoline with an octane rating of 87 or higher.
If 87 octane fuel is used, do not perform any aggressive
driving maneuvers such as wide open throttle
applications. You may also hear audible spark knock
during acceleration. Refill your tank with premium fuel as
soon as possible to avoid damaging your engine. If
you are using gasoline rated at 91 octane or higher and
you hear heavy knocking, your engine needs service.

2005 STS Manual:

Gasoline Octane
If your vehicle has the 3.6L V6 engine, use regular
unleaded gasoline with a posted octane of 87 or higher.
However, for best performance and for trailer towing,
you may wish to use middle grade or premium unleaded
gasoline. If the octane is less than 87, you may get a
heavy knocking noise when you drive. If this occurs, use
a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.
If your vehicle has the 4.6L V8 engine, use premium
unleaded gasoline with a posted octane of 91 or higher
for best performance. You may also use middle
grade or regular unleaded gasoline rated at 87 octane
or higher, but your vehicle’s acceleration may be slightly
reduced. If the octane is less than 87, you may get a
heavy knocking noise when you drive. If this occurs, use
a gasoline rated at 87 octane or higher as soon as
possible. Otherwise, you might damage your engine.

Aurora5000
03-14-07, 08:48 AM
From '06 owners manual

If your vehicle has the 4.6L V8 engine (VIN Code A), use premium unleaded gasoline with a posted octane rating of 91 or higher.

You may also use regular unleaded gasoline rated at 87 octane or higher, but
your vehicle’s acceleration may be slightly reduced, and you may notice a slight audible knocking noise, commonly referred to as spark knock.

After a year of driving, I have not noticed any engine knocking noise due to pre-ignition. I have not noticed any loss of acceleration (I do WOT to 80 every day.) If I start hearing or feeling problems, I will adjust. The 87-88 octane works just fine in my V8. I try to fill up in the same place each week.

The experts say to follow the recommendations in your car's owners' manual. I am using one option which is suggested because these days, the only thing you want to burn in your car is gas, not money.

Jesda
03-14-07, 12:19 PM
If there was an interest in saving money, we'd all be driving Corollas, and this place would be called Toyotaowners.com. :)

cooncat
03-14-07, 01:16 PM
Hey Jesda, that is so try as I drive my premium needy gas hog. What do you drive? You may have told me at the meet and I don't remember. You would love the weather down here right now.

bob

malatu
03-14-07, 06:49 PM
I must have gotten a bad batch of gas. At stoplights the car chokes then recovers. I have had problems with his particular brand of gas before in a Pontiac Grand Prix.

I was wondering what octane is best to use? I have been putting in 89. Here in the midwest, most stations carry 87-89-91. I was wondering if I should start putting in 91 in the future (and a different brand obviously).

Anyone else have their car choke at stop lights?

Thanks

The following is a response I read a while back on another forum. The response is to a similar question but the engine is a supercharged 3800. This may or may not be applicable to the northstar. If the commonality is a "High Compression" engine, this may apply.... The question was, "Do I have to use high octaine in my bonneville ssei superchaged engine?

The following was a reply ..... take it for what it's worth....
Well... the short answer is not immediately, no. But the long drawn out answer is: Yes. The higher octane is needed for the supercharged engine because of increased temperatures and pressures in the combustion chamber. If you didn't already know, the higher the octance the slower is burns and the higher the temperature needs to be to ignite it. If you use low octane gas, which burns quickly and needs a lower temperature to ignite, it can cause detonation, which is the air/fuel mix ignition before the spark plug ignites it. This is very bad, and can cause piston and spark plug damage. Now, your car DOES have means of counter-acting detonation (or knock) by electronically adjusting timing until it senses that the knowck has been relieved. The downfall of this is that you lose power. No one wants that. So the best way to go is plunk down the extra .05 to .15 cents and get the good stuff.

Curious George
03-15-07, 02:40 PM
Like many Northstar STS owners, I started refueling with 91 octane premium. Whilst on extended road trips, cruising for hundreds of miles on straight and level highways, I noticed that I rarely dipped deeply into the throttle. Figuring that I had no need in those circumstances for the knock and detonation protection offered by premium fuel, I'd fill up with 89 octane mid-grade (with some trepidation at first). Noticing that my car didn't hack up hairballs or eject the odd piston, the trepidation faded and I came to enjoy the 10 cents per gallon discount.

Last Summer I drove across Canada on Hwy 1. Outside major cities, 89 octane fuel is generally unavailable. You choose between 87 octane regular or 91 octane premium. Across Manitoba and Saskatchewan, both flat as Kansas along the southern border, I chose regular. Guess what? The car ran just fine. Epiphany! My car has been thriving on a steady diet of 87 octane regular ever since. The odometer reads 27,983 miles just now.

The only place where 91 octane makes a measurable difference to me is at the drag strip, where it appears to shave 0.2 second off my quarter-mile time. (100 octane racing unleaded fuel is even better.) Premium fuel might make a difference to others who drive in more severe conditions than do I.

Jesda
03-16-07, 06:30 AM
Hey Jesda, that is so try as I drive my premium needy gas hog. What do you drive? You may have told me at the meet and I don't remember. You would love the weather down here right now.

bob

I've got an olllllld 1990 Infiniti Q45 with 167k now.

Aurora5000
03-16-07, 10:21 AM
Here is some good info. about Detonation/Pre-ignition.
I copied 2 paragraphs directly referring to Northstar engines.
Full article:
http://www.germanmotorcars.com/Detonation.htm

There are a lot of reasons for fast burn chambers but one nice thing about them is that they become more resistant to detonation. A real world example is the Northstar engine from 1999 to 2000. The 1999 engine was a 10.3:1 compression ratio and was designed to use premium fuel. For the 2000 model year, with a revised the combustion chamber and faster burn it is designed to operate on regular fuel and the compression ratio only had to be lowered .3 to only 10:1 to make it work. Normally, on a given engine (if you didn't change the combustion chamber design) to go from premium to regular fuel, it will typically drop one point in compression ratio: With our example, you would expect a Northstar engine at 10.3:1 compression ratio, dropped down to 9.3:1 in order to work on regular. Because of the faster burn chamber, it only had to drop to 10:1. The 10:1 compression ratio still has very high compression with attendant high mechanical efficiency and yet it can operate it at optimum spark advance on regular fuel. That is one example of spark advance in terms of technology. A lot of that was achieved through computational fluid dynamics analysis of the combustion chamber to improve the swirl and tumble and the mixture motion in the chamber to enhance the burn rate.

Consider the Northstar engine. If you do a full throttle 0-60 blast, the engine will likely run up to 6000 RPM at a 11.5:1 or 12:1 air fuel ratio. But under sustained load, at about 20 seconds, that air fuel ratio is richened up by the PCM to about 10:1. That is done to keep the spark plugs cool, as well as the piston crowns cool. That richness is necessary if you are running under continuous WOT load. A slight penalty in horsepower and fuel economy is the result. To get the maximum acceleration out of the engine, you can actually lean it out, but under full load, it has to go back to rich. Higher specific output engines are much more sensitive to pre-ignition damage because they are turning more RPM, they are generating a lot more heat and they are burning more fuel. Plugs have a tendency to get hot at that high specific output and reaction time to damage is minimal.

dkainsworth
04-18-10, 12:00 AM
Well, I am not downing anyone for the decision that they make about their own vehicle. But, I have a 2000 Cadillac STS and I recently let my brother drive my car for a sum of 4 to 5 day off and on and boy did I **** up. I have always put premium gas in my car and he put regular in it for the few days that he drove; and when I got in my car to go to the store I was hurt to hear my car sounding and running like that. I have got new spark plugs, boots, and fuel filter and I still have the same problem. I am pretty sure that my problems came from the wrong octane of fuel.

Pjazz
04-18-10, 12:55 AM
Hi I just recently purchased my 07 STS 8V RWD. I also think if you pay this kind of money for this type of car you should go by the manufacturers Recomendations. There is no big conspiracy. It's been known an proven for countless years that if an engine is designed for a certian Octane then it's optimal performance will be acheived by that Octane.

To me running a lower Octane in a hi performance engine is like thinking you can drive an extra 50 miles with your oil light on. You may make it but you don't know what you're doing to your engine. I love it how some of you are saying you can hear and feel no difference in performance. I don't really see how you could tell as quiet as these engines run.

My wife decided to start using 89 in our 2000 BMW in which the owners manual states 91. Months later she had a problem starting the car. I checked the plugs and they were black and fouled. Lastly those of you who don't put the recommended fuel in the car how about telling the person you sell the car to, so they can make the decision if they want to buy it or not.

CadillacSTS42005
04-18-10, 08:46 AM
Thread back from the dead!

That said, you gotta pay to play, you bought the car, maintain it right.
That said I use 93 (whats considered premium in PA) and when I stop to top off for a long trip I add 89, I figure the higher octane rating I already have in half the tank will balance out the lower octane I just added.

KRSTS
04-18-10, 10:16 AM
Well, I am not downing anyone for the decision that they make about their own vehicle. But, I have a 2000 Cadillac STS and I recently let my brother drive my car for a sum of 4 to 5 day off and on and boy did I **** up. I have always put premium gas in my car and he put regular in it for the few days that he drove; and when I got in my car to go to the store I was hurt to hear my car sounding and running like that. I have got new spark plugs, boots, and fuel filter and I still have the same problem. I am pretty sure that my problems came from the wrong octane of fuel.

More than likely cheap inferior fuel.:banghead:

next2pool
04-18-10, 12:12 PM
These cars have knock sensors and will adjust timing to prevent detonation. Using a lower octane fuel isn't going to hurt them a bit--you may get reduced performance if premium was recommended. If regular is recommended, using premium will not only be a waste of money, but will reduce fuel economy. Premium gas slows down the flame front in order to reduce detonation--that effectively has the same effect as retarding timing. Remember that premium has no bearing on the quality of the fuel. Many complaints mentioned here are due to poor fuel quality--not octane level.

malatu
04-18-10, 12:28 PM
Once you understand the characteristics of fuels and their octane rating, you'll begin to realize higher octane fuels aren't better than lower octane fuels ... they're just different. The title of this thread, "What Octane is Best?" can't be answered. The title should read, "What Octane is Best for my Car?" I sort of chuckle at some of the rational some folks use to put in fuel different than what the manufacture recommends. I would suggest the more expensive dog food is better for your dog but the more expensive (higher octane) fuel isn't better for an expensive car.

I suggest "better" fuels are the "top tier" fuels that have appropriate additives. And to be honest with you .... I"m not 100% sold on the additional qualities these top tier fuels offer. Then again, that could be my ignorance.

turnne
04-18-10, 12:51 PM
I had a 2000 sts, got in 2002 and just got a 2005 (dec) and have only put in 87, call me cheap - but i have had no problems at all . I have put 91 and 93 in during the cold months and gas antifreeze. NO PROBLEMS AT ALL.....

+1

I had a 2002 STS and now the 05 STS....both always run on 87 octane ...
Just like the owners manual says..it will run fine

That was part of my reason for buying the car....its the only luxury V8( besides the Hyundai Genesis) that the manufacturer states will run fine on 87 octane


Warren

turnne
04-18-10, 01:09 PM
Here's how I see it......

When they were the one's to print in the owners manual that premium is strongly recommended and the use of regular could cause damage to the engine. Again.....each of us can use whatever octane we want....just be prepared if damage occurs. And seriously, I don't mean to be a pain, but if we can afford payments ranging from 600-800, we should be able to afford the premium gas to put in it. Just my opinions here! :-)

Where does it say that in the owners manual?

on page 5-5 of my owners manual is states

"if your vehicle has the 4.6LV8 engine, use premium unleaded gasoline with a posted octane of 91 or higher for best performance. You may also use middle grade or regular unleaded gasoline of 87 octane or higher, but your vehicle's performance may be slightly reduced"

I don't think I want to touch the financial standpoint of these cars...if you were the first owner..I guess I can understand some of that
But anyone that bought the car 3 plus years old paid SO VERY MUCH less that I think that is a moot point

Case in point..I traded in a 2002 STS with 123K miles..in excellent shape..I got $3500
One of my reasons was that I felt that there could easily be a repair looming...like the electronic suspension...that would cost more to fix than the car was worth

So I ask you the question...would you put $4000 in a car that was worth $3500( fixed)?


Warren

KRSTS
04-18-10, 01:26 PM
Y'all put in whatever lights your fire. As P.T. Barnum said............:yup:

malatu
04-18-10, 01:41 PM
Y'all put in whatever lights your fire. As P.T. Barnum said............:yup:


.... and I chuckle again ...:histeric:

turnne
04-18-10, 06:23 PM
If there was an interest in saving money, we'd all be driving Corollas, and this place would be called Toyotaowners.com. :)

or alternatively..if you didn't care about money there would probably be a lot of members that could call Mercedesowners.com home :)


I would think that most everyone here cares about money...these are not nearly expensive enough to put someone in that category


Warren

EChas3
04-18-10, 06:29 PM
"You may also use middle grade or regular unleaded gasoline of 87 octane or higher, but your vehicle's performance may be slightly reduced"

... Seems clear to me...



So I ask you the question...would you put $4000 in a car that was worth $3500( fixed)?

Value can be tricky. Is an object's value what a buyer will pay or what it costs to replace?

turnne
04-18-10, 06:40 PM
Value can be tricky. Is an object's value what a buyer will pay or what it costs to replace?

What the market will be bear for a sale...in theory they should be the same
Or put another way...use the same valuation that an insurance company uses.
One that either is A. responsible for paint and body work on a collision claim or B. A warranty company...non GM certified....every one I have seen in recent years has a clause about the covered repair not exceeding the book value of the car

Or put in the perspective of an owner......I have seen many pre 2000 northstar equipped cars over the years with HG issues. Many of which where the owner junked the car...and frankly some of them were very clean except for that issue
But again...the repair was much more than the car was worth...seems that many just decided it made sense to sell the car for salvage and buy another car


Warren