87 89 91 Octane Levels

[jinxed45]

I know that they're different octange levels and the higher octane, the higher quality, but how does it affect my Caddy. And how do you know? Thanks.

[Flyer]

the higher the octane, the slower burning the fuel. The slower burn produces a more even combustion, preventing hot spots and making a little more power. I'll bet Guru will hit this post, and give you a much more in depth explanation...

[Bentham]

I've wondered the same thing.

and also..., why is it one gas station price for 89 is 1.82

while 1 RIGHT across the street (for 89) say... is 1.88

Isn't gas ---gas ?

[Ranger]

Octane is simply the fuels ability to resist knocking. It doesn't provide any more power. The Northstar however will detect spark knock with lower grade fuels and retard the spark to compensate therefore slightly reducing performance, though I personaly have not been able to tell the difference.

The difference in price is simply because people will pay it. Some people have an allegiance to a certain brand and will buy it at any price. Others will price shop. That said different brands will have some different additives. Other than that, gas is gas.

[Bentham]

I don't want to start a war but would it be true in saying the same about oil.. ie ) 'oil is oil' whether you use Quaker State or Mobil 1 ?

-Eric

[Ranger]

I don't want to start a war but would it be true in saying the same about oil.. ie ) 'oil is oil' whether you use Quaker State or Mobil 1 ?

-Eric

Ohhhh boy Heeeaaar we go

[jinxed45]

So since this is the case, then paying that extra 30 - 45 cents will make up for itself through fuel economy? Or maybe it won't? I get about 18.5 MPG now that I've slowed down a bit. (gas is getting expensive!!)

[Greg P.]

So since this is the case, then paying that extra 30 - 45 cents will make up for itself through fuel economy? Or maybe it won't? I get about 18.5 MPG now that I've slowed down a bit. (gas is getting expensive!!)

No, I can't see how using premium or regular will make any differnce in fuel economy.

I ran both in my 99 STS, never noticed any difference.

[Greg P.]

I don't want to start a war but would it be true in saying the same about oil..  ie ) 'oil is oil'  whether you use Quaker State or Mobil 1 ?

-Eric

Yeah oil should be its own other thread. Lots of stuff to talk about but...

In a nutshell, you can use any of the popular brands in the correct weight. Should be 10W30 for your car. I would check the label to see that the oil meets the GF3 standard or better. Other than that, there is no particular advantage to one brand over another.

Check this out: http://www.xs11.com/stories/croil96.shtml

As far as Mobil1 or any of the synthetics. While these are fine oils, they offer no real advantage for your Northstar engine.

Also, do not use any oil additives. All popular oil brands contain their own additive package. Additional additives offer no advantage and may in some cases cause harm.

[Flyer]

You said it yourself Guru,

The only difference in the fuel is it's resistence to that spontaneous combustion

That resistance is called slower burning in laymans terms. Resistance by definition "reduces" flow. I didn't say the difference was huge, but there is a difference on the scale of combustion. Higher octane fuel burns more evenly by burning slower and less chaoticly.

You know you don't always have to pick a fight when I put something into laymans terms for all of us laymen out here...

[Flyer]

Guru,

I'm afraid that you are contradicting yourself...

No difference in burn rate.

This is easy to prove as , if there WAS a difference in burn rate between fuels, an engine would make different power levels on different fuels and/or the spark timing would have to be adjusted to account for the change in burn rates. This doesn't happen

You just said:

The 93/99 Northstar engine is designed and optimized to operate on premium fuel. The compression ratio and the spark advance programmed into the PCM are optimized to make the most power and best economy on premium fuel

It sounds like the spark advance is tuned for "premium" fuel, not tuned for "regular", does "timing" ring a bell?

Engines DO make different power levels on different grades of fuel, 3.8L supercharged engine of my bosses made 362 HP at the wheels with 93 octane, and 392 HP with 110 octane.

Here you say it yourself:

What does it mean to you??? You can run most any grade or octane rating of fuel in a Northstar without worrying about engine damage or anything. You might notice some slight degradation in power/economy/driveablity on hot/dry days or very cold/dry days. If you do, then use a higher octane fuel

A slight degradation in power? That is called:

...different power levels on different fuels and/or the spark timing...

Who are you to designate what the "within practical reason" limits are for this discussion?

All gasoline burns at the same rate (within practical reason..at least close enough for this discussion).

Your statement is not absolute with regards to the differential burn rate of various octanes, therefore I see no reason for your argumentative reaction to my post:

sorry Flyer to pick on you here...but you get to be the "messenger" that gets shot...LOL

I'm by no means suggesting that I know more than you about the subject, but I am a little put off that you have to argue with a statement that is easily understood by the masses of people who might want to know the crux of the fuel ignition mechanism without reading through your lengthy discriptions.

Add to the thread, instead of deconstructing it please.

[ScottP]

Adding alcohol increases the octane rating.  MMTBE and other compounds increase the octane rating.  Alcohol burns slower than gasoline....so...a "premium" fuel spiked with 10% alcohol to get the octane rating (common) will burn a little slower.

Is there any effect, detrimental or beneficial, to using fuel which is marked at the pump "contains XX percent alcohol" in a Northstar engine? One gas station in my area has a sign on its pumps "MY gas contains NO alcohol." Is this better for my NS or does it matter?

[Ranger]

So since this is the case, then paying that extra 30 - 45 cents will make up for itself through fuel economy? Or maybe it won't? I get about 18.5 MPG now that I've slowed down a bit. (gas is getting expensive!!)

No. Burning 93 will not make up the difference in price in MPG. The difference will be minimal. When I switched from 93 to 87 I saw little to no difference. Infact I think it actualy increased by .05 -.08 MPG.

[Rickster]

Hey FLYER..... not getting any?

[Flyer]

Hey FLYER..... not getting any?

Rickster, read a post that I have made, attack it for no other reason than to be argumentative and a know it all, and see if you don't get the "not getting any" treatment also.

[Rickster]

Hey FLYER. I hear ya. I was just trying to add some humor. LOL

[Norton1]

All I can say is that I am now aware that I can burn lower grade fuel in my car without worrying about it knocking or harming the motor. I was burning premium but tried the mid-grad fuel and appear to be getting the same mileage. So next tank is the cheap stuff.

Thanks all for your input -

Steve

[Norton1]

Well after a tank of mid-grade and a tank of the cheapo - I'm impressed. I was getting 20.5-6 on the Premium - with the cheapo I'm getting 22.7-23.

What I noticed is the car does not accelerate as quickly on cruise, the resume piece of it, and runs on the freeway absolutely the same as it did on Premium.

So unless I take to drag racing I think the cheap stuff is a much better deal.

Thanks again

Steve

[jinxed45]

I also switched from 91 to 87.. not too big a difference either way.. just depends on how i'm driving. i don't even feel too much a power difference.. but saving on gas.. that's always good..

[Marika]

Unfortunately, the 4.9 doesn't have the knock sensor so I guess I'm sort of stuck with expensive premium.

[msilva954]

Chevron---Premium----nuff said.

[Marika]

Unfortunately, the 4.9 doesn't have the knock sensor so I guess I'm sort of stuck with expensive premium.

You can certainly try lower grades of fuel in a 4.9. Just listen for spark knock. If it knocks, use a higher octane grade or switch stations for the same octane.... It will not hurt the engine to let it ping or spark knock a little. The premium repuirement is there to guarantee no spark knock under any condition. If you are towing trailers thru Death Valley in the summer you might want to stick to premium fuel.... otherwise, under less stringent conditions lower grades of fuel wil probably work fine. If you do notice any spark knock I would check the EGR tubes for cleanliness as restricted EGR tubes will cause spark knock more frequently than lower octane grades of fuel in the 4.9. The other option with the 4.9 is a slight spark retard. Enter the set timing mode by grounding pins A and B together at the ALDL connector , use a timing light, and bump the reference setting of the distributor down to 8 or 6 degrees instead of the 10 degree factory spec. This will enable you to run regular fuel with no spark knock. A little bit of experimentation will tell you what fuel requires how much spark retard. This is all that the knock system does...it senses detonation and retards the spark until the detonation stops...it is automatic on the Northstar but you can accomplish the same thing manually on the 4.9...if you really want to run lower octane fuels.

I guess I could let the tank run to "LO" and then put about $5 of lower octane fuel in and see what happens. This way, if it starts knocking I can fill it up the rest of the way with 93.

I once went for a job interview at an aircraft maintenance company out at Teterboro Airport here in New Jersey. I ended up not wanting the job but during the interview I was told that airplane fuel is simply gasoline but the octane is raised to 100.

Gee, I wonder what my car would do with 100 octane fuel? Fly???? LOL!!!

I understand marine fuel is also 100 octane but it contains lead because of the corrosion problems that marine engines can face being exposed to salt water/air. Correct me if I'm wrong. BBobynski.

Back in the days when we were experiencing the fuel embargo my brother once filled his motorcycle tank with marine fuel he syphoned from my father's boat and the motorcycle took off like a bat out of hell!!

[Jackson]

Since Eric got on the topic,

If "Oil is Oil", is switching back and forth between 5W-30 and 10W-30, depending on the season, make a difference?? I know two mechanics that disagree on what to put in the car and when. Any advice??

-Charisse

[JasonA]

For your '94, use 10W-30 all year 'round. For a 2000 or later engine, use 5W-30 all year 'round. Switching between different weights for the different seasons is simply making it more complicated than it needs to be, especially in most parts of this country. Check your owner's manual to be sure. There should be a small chart in there on the oil viscosity for the temperature. I think it recommends 10W-30 for all temperatures above 0*F (for 93-99 engines). Maybe if you live where it gets REALLY cold in the winter, much below zero, you would benefit from 5W-30 during the winter months.

[Marika]

I guess I could let the tank run to "LO" and then put about $5 of lower octane fuel in and see what happens.  This way, if it starts knocking I can fill it up the rest of the way with 93.

I once went for a job interview at an aircraft maintenance company out at Teterboro Airport here in New Jersey.  I ended up not wanting the job but during the interview I was told that airplane fuel is simply gasoline but the octane is raised to 100.

Gee, I wonder what my car would do with 100 octane fuel?  Fly????  LOL!!! 

I understand marine fuel is also 100 octane but it contains lead because of the corrosion problems that marine engines can face being exposed to salt water/air.  Correct me if I'm wrong. BBobynski.

Back in the days when we were experiencing the fuel embargo my brother once filled his motorcycle tank with marine fuel he syphoned from my father's boat and the motorcycle took off like a bat out of hell!!

Several misconceptions and misinformations here....

Lots of different kinds of "aviation fuel" some is kerosene (jets) some is gasoline (general aviation, piston engines) The gasoline type aviation fuel is just plain old leaded gasoline. The lead improves the octane rating of the fuel. That is why it was put in there in the first place...and then people got afraid take the lead out of gasoline due to the suspected valve seat wear...the lead also lubricated the valve seats so engines were designed with this in mind. Since the general aviation fleet dates back from the era of leaded fuel all the engines were designed for lead (non hardened valve seats) so leaded fuel is still supplied for aviation use only.

Lead was added to the fuel to improve the octane rating, only. It does not make the fuel more powerful nor will an engine make more power with aviation fuel or leaded fuel.... the idea of a motorcycle making more power because suddenly leaded fuel is put into it is....ah....groundless in engineering logic. A Northstar engine (or a 4.5/4.9) will make the same power running on unleaded premium or aviation gasoline. There is no more energy in the fuel due to the octane rating. The higher octane rating would allow the engine to be modified to make more power (compression ratio, timing,etc) but that would require exstensive engine mods. The fuel alone would do nothing.

Aviation fuel is generally very non-volitile. Since it is blended to work in an engine at high altitude it is very "dead" fuel with low vapor pressure. Likely your car would not even start on it in the winter as so little would vaporize....it would drive poorly even if it did start. Aviation fuel does NOT make good racing gas or high performance fuel. It is just designed for airplanes...that is all...nothing really special about it.

Add tetraethyl lead to ANY gasoline and it will improve the octane rating. This was a major scientific breakthru that the Ethyl corporation discovered in the 30's in search of a fuel that would allow higher performance aircraft (piston) engines...it worked well in WW2.

Very little if any marine fuel is leaded anymore. I think it is totally outlawed and/or not available. I don't know about your area, but around the Great Lakes usually regular unleaded is what is available "on the water" at gas docks. Some of the marinas that cater to the high perf boating crowd have unleaded premium but that is all. If you want leaded race gas you have to bring it to your boat in 5 gallon cans.... Many of the hot rod offshore boats in our area have 20 to 50 gallon tanks onboard for race gas....and then they run on the premium unleaded in the main tanks for cruising. Switch to the race gas is accomplished with valves if the need for max speed arises. Marine gas is just like aviation gas and car gas. Nothing magic in terms of power making. If that motorcycle took off like a bat out of hell on marine gas then it would have taken off like a bat out of hell on lawnmower gas from the can.....LOL

The lead in marine fuel was just for the octane rating...nothing to do with corrosion protetion due to the marine environment or anything.

Can always depend on BBobynski to explain things and clear up the un-understandable