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I have a '92 Blazer with a re-built CPI 4.3. Can it run/idle well enough on regular grade gas without having to use premium?
 

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Trance is what I breathe
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I cant see why not... for an unmodified engine, gas is gas
 

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Gas is not gas.My owners manual states use 93 octane.If you don't think using cheap gas will affect your truck, think again.
 

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"Old School"
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try the lower octane ... if there is no knocking then it should be ok for everyday driving ... if it knocks I would switch back to a higher octane


*btw - I only use 91+ in my car and truck
 

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Trance is what I breathe
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for our S Dimes we dont have to run High Octane fuel... Now a Beamer I can understand and a Vette but now our Dimes
 

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Octane is a resistance to detonation. If your engine doesn’t knock…don’t knock the fuel. The often quoted theory that “it runs better, has more power and/or better fuel mileage” is a simply an old wives tale. I read in an in-depth article that said high octane fuel will not give you any more power…not even one little bit. The article simply stated that high octane will allow you to make more power thru a mechanical means. The article was written by a pretochemist that works for Unocal. High octane fuel is for high compression engines such as Vettes, Z28s, and other high performance cars. I believe the compression ratio of 4.3’s is 9.5 to 1. I would go by the owner’s manual. My 1994 LT-1 Z28 has a sticker on the inside of the fuel door that says “high octane fuel recommended” I have used 93 octane fuel in it since I bought it new. I unless you add nitrous, a blower or mechanically raise your compression or want to increase your timing, I would stick with the 87 octane gas. Be aware however, if your engine pings, it could be a sign that it is running too hot. High octane fuel used in this situation will cover up the true problem. Hope this helps…Shimaze
 

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Road Race/Auto X S10
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pyros46290 said:
oops sorry i H8 double postin. get my point across tho heh
lol

What does that paper say? There is a gas station around here that sells 112 octane but you can't put it in your car :wtf: It has to go into a container. To weird, all I can say is I luv the way race gas smells. :drunk:
 

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Muff Divin' Member
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premium will give you more combustion because the piston will travel down further until the spark causes the explosion and pushes the piston back up, thus the piston travels up and down for a longer distance giving more momentum and increased power.....at least thats what i thought
 

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96s10 said:
lol

What does that paper say? There is a gas station around here that sells 112 octane but you can't put it in your car :wtf: It has to go into a container. To weird, all I can say is I luv the way race gas smells. :drunk:
i dont remember what the paper said. i took that pic last sunday when i went to an american le mans race at sears point
 

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does all unocal stations sell that real high octane stuff? if so im headin that way soon to get some for my dirtbike. regardless of what people say, VP Race fuels did a test on a stock CR125 engine and it gained 1.5 HP using 112 octane C12 race gas compared to regular 93 octane. and the comp. ratio for that engine is like 8.5:1 or sumthing. so if you gain that much in a 125CC engine imagine the gain in a 262CI engine.
 

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on a dirtbike switching to a high compression head (only reason race gas is needed), will add alot more torque but only a little more power (1.5hp). i know on my 250R i noticed alot better torque when i installed a high compression head.

but back to trucks, i dont think we can use that gas anyway.... isnt is leaded? i know the vp12 i use is. i dont think there would be any gain anyway.
 

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2 strokes are alot more sensitive to changes in altitude, humidity, temperature and all that so you have to adjust the carb's on them alot more often than a 4 stroke, but if youre a guy like me who loves working on them then thats good...to a certain point. then it gets aggravating sometimes. i like 4 strokes too but i love the sound and smell of 2 strokes. and i think leaded fuel in our trucks will make some sensors like the o2 sensor go crazy but leaded fuel would help make a little better power.
 

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s10_xtreme said:
premium will give you more combustion because the piston will travel down further until the spark causes the explosion and pushes the piston back up, thus the piston travels up and down for a longer distance giving more momentum and increased power.....at least thats what i thought
Oooh, where to begin. Unless your engine is inverted (it's not) then the combustion pushes the piston down. The pistons travel is determined by the crankshaft and rod, the distance the piston travels does not change no matter what you do (unless of course you break something in a very spectacular manner). The momentum of the piston is not really a factor. And premium gives you less combustion.

The spark actually occurs before the piston reaches TDC (top dead center), and the flame propagates across the cylinder at a constant velocity. In knocking combustion (caused by too high compression, too much timing, too low of octane, etc.) the flame front begins to travel across the cylinder at a constant velocity, then almost instananeously, the rest of the mixture explodes. This sends a very high frequency shock wave through your engine, which is heard as a pinging noise, and can cause serious damage.

Octane is a measure of resistance to preignition. In other words, the higher the octane, the harder it is to burn the fuel, and the less power is contained in a given volume of fuel. Premium gas contains less energy per unit volume than regular gas. If you run premium fuel in a vehicle that does not need it, you will get less power and lower fuel economy.

Some cars (like my lincoln) have high enough compression and timing that is advanced far enough to take advantage of higher octane fuel. The engine would ping if you put regular in it. Actually, the knock sensors would notice the ping and retard the timing, so you'd just lose some power/economy.

I don't think S10's run enough timing to take advantage of premium fuel, but i could be mistaken. If you want a little more power, you can advance your timing a bit, and at some point, you will begin to need premium. Some older engines may have deposits in the combustion chamber that take up space and thus raise compression, which may create a need for premium fuel (or a good cleaning).

To determine which octane level is best for your needs, keep close track of your fuel mileage, and check all different grades. You will notice that one octane level will be best, too high and you're not running enough timing to take advantage of the extra octane, too low and you'll get pinging/retarded timing (depending on the engine control system) and less power/economy.
 
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