What Octane Grade Fuel for 3800 SC?

Hmm, odd. I use 92 at my local Pilot which is only 1 octane greater and the Riv loves it. I tried Shell V-power and the car ran like crap (could've been that gas station but I haven't been willing to overpay/risk it again - V-power is expensive compared to other premium sometimes being .25-.30 higher than 87) and I think V-power is 93 or 94.

well shintsu my guess is 93. my shell around here has only 93, 89, 87 available. I usually get my gas from citgo who has pretty decent gas at 93. but i used KWIK TRIPS 91 octane. key word is KWIK TRIP they suck so bad.

lol, like getting some gas from "Bob's gas station". Heheh - this here 90 grade is our premium and it's reaaaal good.

does anybody around here cheat occasionally,and buy 87?

N E V E R .

never?

NEVER - Always 93 octane.

never. 93 no matter what is cost.(and i'm a broke college kid)
Take a look at a the data with a scanner and watch what happen when you introduce low octane gas...not worth it, even for a stock riv or s/c car.

Never. Don't do it unless you like chipped pistons or want to replace your head gaskets.

that bad/ shit.. gallon of gas approaching $3

robotennis61 wrote:

that bad/ shit.. gallon of gas approaching $3

How many miles do you drive? You are talking about the difference of $3000/year in gas vs $3100/year in gas? Vs saving and paying $2700/year in gas, but risking your motor...

technically the minimum octane requirement I believe is 91. If you are have mods, especially including a smaller pulley, you want as much octane as you can get. Supercharging creates hot air. Smaller pullies create hotter air! Heat will bring detonation. Octane is required to counter the detonation. So, devise a S1 intercooler, or run the octane!

premium gas is actually recommended by Buick for these cars. And when the cars are significantly modded like my brothers you need every bit of octane you can get. If you manage to run out of gas you can use unleaded to help you get home but I would not recommend unleaded for everyday use

E85 cough cough..

deekster_caddy wrote:

Never. Don't do it unless you like chipped pistons or want to replace your head gaskets.

Can you show my evidence of this? I've put a loooads of miles on my Riv running 87 and sometimes 89. Granted I don't always put my foot in it, but I do at times.

I put endless amounts of miles on an STS that called for the same and never had any issues (with the motor) I think this 93 only or you're car is going to go boom is overhyped.

Well maybe the Knock Retard is working overtime for you.
But at just $ .10 cents per gallon more I'd rather run the 91 or 93 octane.
Amounts to about $1.80 per fill up.

What year STS? Some of them required premium, but for some it was only recommended.

The topic of knock and using low octane fuel has been beaten to death in this thread. No one has to prove or demonstrate that knock is bad for pistons, and no one needs to run 87 to create knock. It's just common knowledge, like putting sugar in the gas tank. Here's what we know for sure:

• Sustained, heavy knock in supercharged applications will chip pistons. If you have doubts, please read this: http://www.misterfixit.com/deton.htm

• Using low octane fuel where premium is required will create the conditions for spark knock to occur. This is why octane is also known as "anti-knock" rating. By definition, an engine designed to run on 93 will knock on 87.

• Knock occurs at different magnitudes, depending on how much heat and compression exists in the combustion chamber. For this reason, brief or low-level instances of knock may not damage pistons much, but that all changes when you run the engine as it was intended. For this reason you can get away with using low octane if you drive around at the lowest RPMs, avoid hills, and don't run the car on really hot days, but try for the rated 240 HP and only bad things will happen.

If you want your Riviera to have "retarded" performance, use 87 or 89 octane. Just because the engine doesn't blow up or make noise, it doesn't mean everything is okay. The engine is taking steps to protect itself by retarding timing. You cannot see or hear this happening. Until you hook up a scan tool and witness the car pulling timing to avoid possible destruction, you don't have a clue what you're doing to a car by using 87 octane.

The PCM is even smart enough to switch to a "bad gas" spark table if someone uses low octane fuel and runs the engine to its potential. The result is much retarded timing (and lower performance) in order to run with less risk of chipping pistons.

If you don't want to buy 91+ oct gas, don't buy a supercharged car that explicitely says it needs premium. A lot of caddy's, northstar or not, require premium too. I was pretty surprised that my friends '94 deville 4.9L requires premium too. He testifies it runs noticably better on 91 than 87 anyway.

There are things you can actively do to get away with using lower octane gas but for anyone who actually likes to drive the car, it's counterproductive. The product is ultimately a less powerful car and unnecessary risk.

How you drive can possibly have a lot to do with your risk. If you drive the car like grandma 98% of the time and punch the gas every once in a blue moon, that's NOT ok. The last thing you want is to punch it when the PCM isn't even prepared for shit tons of knock - ie running a good fuel timing table, etc.

Just wondering if it is essential for the supercharged engine to have the premium gasoline. Would regular gas really mess up my engine?

DJ

Yes, the extra octane helps control knock and running lower octane makes your PCM do lots of extra work trying to pull back timing to keep your pistons from grenading. You could probably get away on 87 but there's no telling how long until that one time you put the pedal down to pass someone and BOOM

If you go WOT for 5 minutes on 87, you'll be shopping for new cylinders, rods, a lower end, valves, valve covers, a hood, crankshaft, cams, etc., because they will have shattered, cracked, or been otherwise demolished.

IBx1 wrote:

If you go WOT for 5 minutes on 87, you'll be shopping for new cylinders, rods, a lower end, valves, valve covers, a hood, crankshaft, cams, etc., because they will have shattered, cracked, or been otherwise demolished.

Well I wouldn't go that far, the 3800's a little stronger than that! The pistons will just look like this:

IBx1 wrote:

If you go WOT for 5 minutes on 87, you'll be shopping for new cylinders, rods, a lower end, valves, valve covers, a hood, crankshaft, cams, etc., because they will have shattered, cracked, or been otherwise demolished.

or if you're a boss like travis is, you can do the same thing on 93 and still be shopping for parts above. It's not worth the risk; use the gas the the manufacturer requires

I normally just run 87 with a Lucas booster to bring me up to around 90 same basic priciple. 1-2 octane points are not going to decide whether or not your engine blows, and if so you probably had a problem long before that happens anywayz. Just figure out which is cheaper premium or running reg with a booster, or even try both and see which you prefer.

Hometown Hero wrote:

I normally just run 87 with a Lucas booster to bring me up to around 90 same basic priciple. 1-2 octane points are not going to decide whether or not your engine blows, and if so you probably had a problem long before that happens anywayz. Just figure out which is cheaper premium or running reg with a booster, or even try both and see which you prefer.

Would you rather spend ~20 cents more per gallon at fill up, or drop some major cash on an engine rebuild, especially if you can't do the work yourself? If you cant spend the extra few bucks then buy a car that runs on 87. You're just killing power and most likely getting worse mileage since your running such low timing.

See heres my thing, I am swapping to a series III and I really could care less about the health of my Series I. So why should I spend an extra $ at the pumps when I can put it towards the series III?