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Discussion Starter · #1 ·
On another Chevy forum it was said that for the folks worried about the price of 93 and 91 octane it was okay to use 87 octane. After a 100 miles or so the PCM would adjust and run properly ( with less performance, of course ) on the lesser octane.

So, will the SSR (2003/2004) PCM adjust 'up' after switching from 87 to 91 and 'increase' performance? (91 is premium here in the Seattle area.)

Sounds to easy, but I'd do it, if it will.

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Jim, correct me about this if I'm wrong.

But I think the adjustment that happens, is that the fuel mixture is leaned. When it starts knocking, the mix is set richer. When higher octane is used, you get a leaner mix. Lower the octane, it knocks for a while then adjusts richer till the knock stops.

Better performance has no part in the adjustment, except where fuel mileage is concerned.

If you want better performance, you'll need to have the computer reprogrammed and use the higher octane such tuning requires.
 

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Octane Ratings

When looking at Octane ratings, be aware of the 3 different methods used. GM (and other car makers) typically use the Research Octane Number (RON). There is also a Motor Octane rating method which is about 8 points lower for the same fuel. When the government got involved in the 1970's, they came up with a 3rd method which was averaging the other two numbers. That's why you see the (R+M)/2 on many gas pumps.

These are the octane numbers for different unleaded gasoline grades:

Method Regular Premium
--------- ---------- ------------
Motor 83 89
Average 87 93
Research 91 97

The 87 Octane regular SA13335 is talking about is the fuel GM recommends for the SSR. Using higher Octane fuel usually does nothing except draining your wallet faster. With my SSR, there is some indication that using Premium fuel slightly improves the fuel economy (+ 5% or so), although I continue to gather data.
 

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I don't care how much high octane costs. When I cruise up to the pumps in my awesome black ssr, with the top down, of course, there's no way I'm ordering anything but the most expensive gas when I flip my credit card to the attendent.

God would probably strike me dead if I ordered regular!

:lol
 

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HOTRODCHEVY is right. I burn nothing but regular and it runs great. I started out burning super until I read the owners manual. When I switched I saw only a slight change in MPG and noticed no power change. :cool :cool
 

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There will be less horsepower produced with the lower octane fuel. I am not sure how much less. Most people probably cannot tell the difference.
 

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Two different cases to consider:

When you use lower octane fuel in an engine designed to use high octane fuel:

The PCM retards the timing to compensate. That reduces both power and fuel mileage compared to stock.

When you use higher octane fuel in an engine designed for lower octane fuel:

You CAN almost always run more spark advance if you use premium versus regular, but the PCM won't by itself advance the timing beyond what was stock setting. You would have to do that via PCM reprogramming.

In EITHER case (low octane or high octane engine) what the microtuners do to get a bit more power is advanc ethe timig beyond what the factory set it at. But, the microtuner instructions correctly warn you that you must not pull trailers or otherwise put the engines under load at low rpm when running this extra timing setting, as the extra advance on the timing will at a minimum cause detonation which will prompt the PCM to retard timing a LOT, or at worst, will put a hole in a piston.

Finally, the premium grades of fuel often differ from the lower grades not only in octane level but also in additive formulation. The lower grades get the chepaer additive packages, while the premium grades get the better packages. My view is that if you spend $40+ k on a vehicle with a sophisticated engine package, it does't make much sense to run cheap additive packages in it to save a tiny bit on fuel.

Jim G
 

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Discussion Starter · #9 ·
Thanks Jim.

I agree about saving pennys.

The question here was "does upgrading fuel work in reverse of downgrading fuel".

I believe you answered that with your comment the PCM won't move timing up past stock setting. That is what I was asking.

Thanks
Skip
 

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Some Science Needed

When we run accurate performance on the turbine engines that we produce, we take a fuel sample and send it to our lab to get the precise physical properties identified. A number of very exacting tests are performed on the fuel to produce a set of variables put into the computer system to correct the data to "standard" fuel. These tweaks are very small, but actually can create an identifiable difference in the engine performance values.

Gasoline is no different. The amount of power (BTUs) available from a gallon of gasoline varies from one brand to another, as does the additive makeup. This is further complicated by the different "grades" of gasoline that could have different refinement processes and/or additives as well.

Take, for example, the difference between "normal" gasoline and the common blend that we run here in Phoenix......

Gasoline has approximately 125,000 BTUs per gallon and "gasahol" (90% gasoline, 10% ethanol) has approximately 121,000 BTUs per gallon. This means that there is about a 3% reduction in the power available from the fuel I am putting in the SSR during certain times of the year here in the city. Hard to measure the difference from the driver's seat, but we know it is there.

I am dead certain that there is a difference in the Specific Gravity, Lower Heating Value, Higher Heating Value and a number of other measureable parameters that affect the true performance of combustion in our engines.

I would love to have a Materials Analysis Engineer from the petroleum industry provide some "standard" comparative data on the energy available from the three different fuels we can choose to put in our trucks.


Sorry for the long-winded spew of a post, but I feel that there is true technical data missing here and I know only enough to ask for expert help.

Later,

Mike
 

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Difference between 5.3 and 6.0 engine and gas used?

I have a Honda VTX 1800 which also uses regular (87 octane) gas. My friend and I both tried preminum (91 octane) gas in our VTX's, and found it did nothing for our power or mileage in our motorcycles. The manufacturer, Honda, said use regular gas and we found that it worked just fine, and we saved money over preminum gas.

Now with the Chevy SSR, I thought I read that the 5.3 liter engine in the 03's and 04's uses regular (87 octane) gas as it is stated in the manual and all the literature that I have read about the 03 and 04 SSR's. I haven't seen it written anywhere that preminum gas (91 octane) is needed or will give you any increased power or benefit with the stock 5.3 SSR engine.

Based on my experience with my motorcycle and from what Chevy says to use for the 03 and 04's 5.3 engines I use regular gas in my 04 SSR and found I haven't had any problems or pinging which you would expect if the octane wasn't enough with regular gas.

With the 05's and 06's that use the Corvette LS2 6.0 liter engine I though preminum gas is either recommended or stated in the literture to be used, by Chevy. On the CD that comes from Chevy with the 05 SSR (which has the 6.0 engine), it says on it that all GM engines can use regular gas, but for the 05 SSR it is recommended that you use premium (91 octane) gas for full performance.

I think the answer is that for the stock 03's and 04's SSR's, regular gas is fine and should work without problems. If you want to spend more money and use preminum gas in the 5.3 engine you can go ahead but you're not going to get anymore performance or increased gas mileage. You'll only be giving the oil companies more money and looking cool at the gas pump by spending more for preminum.

Now with the 05's and 06's I don't know what's the right answer. Will those SSR's run OK with regular gas? That is no pinging. If you get pinging then you know the octane isn't high enough and you do need preminum gas. Or will you just get lower performance but better mileage with regular in the 05's and 06's? You know based on the recommendation that you'll get better performance with preminum gas, so that's not a question. It's what would happen if you used reqular gas in those SSR's that's the question. Is the 05 and 06 SSR's going to run OK with reqular gas? and correspondingly will you get better gas mileage with regular gas in the 05's and 06's? Will the performance with regular gas be good enough or do you really need preminum gas?

My daughter has a 1999 Dodge Neon that she bought new. It says that it can run on regular gas but the engine is designed so that it will get more horsepower, i.e., more performance if you use preminum gas. We found that the increased performance wasn't worth the additional cost of using preminum gas as long it ran fine using regular, which it did. So she only uses regular gas and saves money over using preminum gas.

So unless you intend to always drive the SSR like you're doing a quarter mile drag race down every street I can't see the benefit of using preminum gas over regular gas if the car will run fine with regular gas. There just aren't any times when I would want to drag race someone with my SSR. The other jerks can challenge all they want, by reving their engines of their jackass Dodge Dakotas etc., but I'm not going to bite and abuse my SSR for a meaningless race.

It has more than enough power stock, to get out of any stituation where I may need some extra power.

Just my thoughts
Carl
 

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As I read my '05 SSR owner's manual, it seems pretty ambivalent about the choice of fuel grades. I don't have the manual handy, so this is not a quote, but it's something along the lines of: the SSR will run fine on regular, and will deliver increased performance on premium. No mention is made of increased gas mileage (IIRC) with premium (or regular), nor any detrimental effects to using regular.

I just completed a 2,250 mile road trip through Colorado; with the higher altitudes (10K-feet+) and many steep inclines, I wanted maximum power/performance, so I burned premium exclusively.

Now that I'm back home in flat, low-altitude Dallas, I question the value of burning premium. Since regular runs about $3/gallon now and premium is 20 cents more, that about a 7% price differential. Maximum performance isn't my objective, and even if premium affords a 5% improvement in mileage, it isn't cost effective. If gas prices go down, the value proposition for premium diminishes further, since the 20-cent differential between regular and premium has remained constant around here since gas was at least half the current prices.

I'm going to switch to regular for a few tanks, and see if I notice a difference. If regular's too lean, there's always mid-grade...
 

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Burnin Premium

freezer said:
There will be less horsepower produced with the lower octane fuel. I am not sure how much less. Most people probably cannot tell the difference.
I need all the ponies I can get to move this piece of lead :glol :glol :glol
 

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Everyone,

Here's something from MASTER Car Technician Mark Salem, when he was asked the question. Mr. Salem does several auto repair segments for NASCAR televison, has a weekly television show about auto repair, a weekly radio auto repair show, owns his own very successful auto repair business in Tempe, Az, and his articles can be seen at NASCAR.COM -
http://www.nascar.com/auto/cct/

*******************************************************

Q: Super or regular unleaded?

A: First, let me make this distinction. Pre 1981 cars do not have the ability to change the timing if the engine is pinging. Cars and trucks made after 1981 have a on board computer that will see the engine pinging and retard the timing to eliminate the ping. Then the computer will try and sneak the timing up, all the time watching to see when the ping comes back. When it does, the timing is moved back a couple of degrees to eliminate the ping.

AAA says only 5 % of the cars on the road today absolutely need super unleaded and I agree. If you in doubt, try this. Have your spouse fill up your car and NOT tell you what fuel they used. Do this 3-4 times. See if you can tell the difference and / or guess which fuel they used. If you can't tell the difference, there is no difference.

I use the cheapest gas I can find in my Corvette. In tests we ran, the zero to 60 time was 1/10 of a second slower with regular when compared to super. Not much reason to pay 35-50 cents more per gallon.

Here's the difference. Regular burns fast, one molecule ignite ten and ten ignite a thousand and they ignite a million. The explosion is similar to a balloon popping. We measure the explosion in milli-seconds. Super burns slower, more like a someone letting a balloon go and fly around the room. One molecule ignites 10, 10 ignite 20, and 20 ignite 30. Now don't start writing me and telling me I'm over simplifying this, I already know it!

So super, because it burns longer, should give you more power, better performance and better mpgs. However, the difference between the two different burn times may only be .8 to 1.2 milliseconds of time and I am quite sure no one I know can feel that. Yes, we can measure that on our dyno in 0-60 mph runs and other tests, but unless you can FEEL the difference, there is no difference.

Are there any other benefits to using super,
like cleaner injectors or a cleaner engine?

No. If you use the cheapest gas you can find, you will save lots of money and when you need to replace, repair, clean your injectors, you'll have plenty of $$ to do that. I can't tell you how many times I bid injector repairs (some as high as $1300 for 6 new injectors on a V-6 Nissan) and the customer says, "But I use super, doesn't that eliminate this repair?" and of course the answer is NO.


Want to read more about what Mark says about auto repair questions?
http://www.salemboysauto.com/salem-faqs/default.asp?Action=Cat&ID=5

**************************************************************

Now, with all that said, I have tuned my SSR with a Superchip microtuner and set the timing to run on 91 octane. So I use the 91 octane. Also if the owners manual says use 91 (05's) then I say use the 91 octane. Follow the manual.

I am curious about something though. With my cars that I have used 87 octane and my friends cars that use 87 octane I have always seen black soot on the tail pipe. With the cars I have that I use 91 octane on I do not have black soot in the tail pipe. However, the SSR is another matter. Even with the 91 octane I have the black soot. The tail pipes of the other cars I have that run on the 91 are relatively clean. When I prepare them for a show or special occasion there is very little soot in the pipe.

Does anyone know why the SSR has the black soot and the other vehicles don't even though the 91 octane is used? (Not to hijack the thread)


:seeya E :seeya

Orange SSR :ssr
 

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ECurtis: I can think of 3 POTENTIAL reasons for the soot in the tailpipe.

1. The higher performance vehicles are often set a little on the rich side to protect the engine under high load. Running rich can generate soot.

2. The Gen III engines, for all their strengths, do have a bit of a problem with oil getting past the piston rings if they are revved higher. SSRs owners tend to rev their engines higher for two reasons: (a) we view them as performanc vehicles despite their weight and truck chassis, and so push the gas a bit harder or rev them higher if we have a 6-speed, and (b) the weight of the SSR requires higher rpm to be used more often even in normal traffic than a lighter weight vehicle would. If this is causing the soot, there will be detectable oil consumption. My own SSR exhibits the soot, but NOT the oil consumption, so I tend to rule this reason no. 2 as "unlikely" in my case, but I know that the 2002 Z06 I had DID cinsume some oil, and that it was a complaint from many owners, and we have the same core engine basically.

3. Vehicle usage primarily for short trips, where the engine spends a disproportionate amount of its time in "warmup" mode. That can generate soot, as the PCM keeps the mixture richer until the engine is warmed up.

Jim G
 

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Thanks Jim

JimGnitecki said:
ECurtis: I can think of 3 POTENTIAL reasons for the soot in the tailpipe.

1. The higher performance vehicles are often set a little on the rich side to protect the engine under high load. Running rich can generate soot.

2. The Gen III engines, for all their strengths, do have a bit of a problem with oil getting past the piston rings if they are revved higher. SSRs owners tend to rev their engines higher for two reasons: (a) we view them as performanc vehicles despite their weight and truck chassis, and so push the gas a bit harder or rev them higher if we have a 6-speed, and (b) the weight of the SSR requires higher rpm to be used more often even in normal traffic than a lighter weight vehicle would. If this is causing the soot, there will be detectable oil consumption. My own SSR exhibits the soot, but NOT the oil consumption, so I tend to rule this reason no. 2 as "unlikely" in my case, but I know that the 2002 Z06 I had DID cinsume some oil, and that it was a complaint from many owners, and we have the same core engine basically.

3. Vehicle usage primarily for short trips, where the engine spends a disproportionate amount of its time in "warmup" mode. That can generate soot, as the PCM keeps the mixture richer until the engine is warmed up.

Jim G

Thanks Jim,

I do tend to take short trips in the SSR but I also have a remote start and I start it about (5) minutes before I get in. During this "warm-up" period I will see if this is when most of the soot is generated.

I will let you know.

:seeya E :seeya

Orange SSR :ssr
 

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I have always believed in using the lowest octane fuel that a car can run on. On older cars you could actually adjust the base timing to compensate for lower octane fuels on many engines. You could also easily find 98-100 octane pump gas so you could use lots of advance with your 12:1 C/R hot rod, for performance. That was then and this is now.

The newer engines with all the emissions controls, knocksensors, and programing, right down to individual timing tables for each cylinder, makes our fuel choices a little less important on a stock modern engine. The new engines will compensate with reduced timing when running fuels lower than the design
octane rating to certain limits.

As I read the design ratings by GM for the 03/04's, it states the 87 octane will work fine in the SSR. The '05/06 however is a different story with an engine that was designed for 91 octane. Most of the reason I believe is due to the 10% increase in compression ratio, different head design and camshaft profiles. To get an additional 90 HP or so out of the '05/06 models with just 40 or so more cubic inches of motor requires some pretty agressive tuning and thus the higher octane requirement. Although the '05/06 may run on 87 I wouldn't make a habit out of using it, IMHO..Of course you could retune an '05/06 to run on 87, but most folks want more performance, not less..I am sure the folks that have installed forced induction on there SSR's wish they could find some of the good old pump 98 octane and tune to it, to get even a few more ponies, as I bet a few pounds of boost must be equivelent to compression ratio's up in the 14:1 or so range.

Sorry if I am rattling on with this post, I usually try to be a little less wordy.

Doug
 

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Do You Remember?

OK, here are questions that will place most of us in a particular age group......

1) What was the Octane rating of White Pump Chevron?

2) What was the price at the pump?

3) When was it discontinued?


Carpe Diem - -

Mike
 

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Back when they had the good stuff at the pump

Hey Mike,

I'm not sure what age group my answers may fall into, but here goes with my recollection:

1. 102 Octane (leaded gas)

2. About 50 cents a gallon

3. Im thinking about 1970, as I was overseas most of the time from 1968 to 1972 in the Navy and not driving.

Maybe someone with a better memory can have more accurate input as I was a real youngster back then..Ha!

Doug
 
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