Key word RECOMMENDED not REQUIRED...big difference and that's where this little debate started from.

 

Premium. To fill the tank, usually about 15 or so gallons, at 20 cents more per gallon than reg. thats $3.00 per tank. Its really a lot less then at first though. I figure most V-8's just require premium. New V-8's like ours can run good on mid grade, but to hell with it, just feed it the best.

 

It's a waste of money, whether it's $3 or not, to run something that isn't required.

 

As the Majority here seems to agree. The LS4 requires premium gas as proven and stated in the owners manual and on chevy's website.

done and done...

 

fyi: LT1's NEED 91+. the combo with the compression/timing/steel heads the car WILL ping.


i have a buddy that had a LS1 and with the alum. heads you CAN get away with 89. fyi.

 

I was wondering about that because when I had mine I used just 87 and ran perfectly fine.

 

If you want the most out of your engine use 91 + oct. Lower grades won't hurt anything

 

Hey, everyone...don't forget we are all friends here!!

07MonteSSGirl, can you post a pic of your dash for everyone to see? I have a friend who had an '02 Camaro SS, and that also had a "Premium Fuel Only" notice on the gas gauge.

As far as use of regular or premium in the montes, I have been using regular in my car for months with no problems. I do notice the difference between regular and premium, but it is not so profound as to warrant exclusive use of premium fuel. I run a tank of premium through every other month to clean it out, then back to regular. We all know that as a "rule of thumb," high performance engines should use higher octane fuel for unhindered performance.

 

Holy Mother of ... I can't beleive that nobody except 07 Monte SS has even come close to bringing up the root concepts of why to run Premium vs. Regular.

AwesomeSS - I don't mean to target you as there are others, but the last post saying using lower grades won't hurt anything is misinformation and can cost people thousands of dollars in repairs. Please take the time to read this post completely to understand why.

The short answer:
You can run regular gas in a premium required/recommended car. You do run the risk of blowing your engine though.

You can also run premium in a car designed for regular. In this case you will actually loose performance.


The long answer:

To start, I don't mean anything in this post as a flame, degrading, or a personal attack. This is just blowing my mind. Bigg J summed it up pretty close saying High Performance engines should use higher octane fuel for unhindered performance. Hopefully by the end of this post you will understand why.

The key concept here is Octane and KR (Knock Retard). My 04 Monte with the M90 supercharger is REQUIRED to use 91+. I put an LS1M scanner on this and STOCK was getting 2* of KR when the boost kicked in. Anything above 5* IS causing engine damage. Now that it is modified, if I don't ever gun it, or say only use the first 15% of the throttle, then I can safely use regular. If I do 20% I will get 3* at the higher end of the RPM's before it shifts.

Since this hasn't been brought up I'm going to assume there is a knowledge gap here - once again I don't want to insult anyone, just educate.

Octane is a measurement of octane and heptane. EG Regular 87 is 87% Octane and 13% Heptane. Fuels with over 100 Octane rating are actually adding Kerosene, Methenol or Ethonol in.

What the Octane Rating actually is, is a number that describe when the fuel will actually spontaneously combust without adding spark. In laymans terms, how quickly/easily it takes the fuel to ignite. When the fuel detonates before spark is applied it is called knocking.

The Octane Rating you vehicle will use will involve a complex formula: What temperature the engine will run at, how hot will the air be going into the cylinder, how much is the cylinder going to compress the air/fuel mixture, and then some other factors such as spark timing and engine reliability (these are to be long life engines) among others.

Back to the lesson: the more you compress gasoline, the easier it is to spontaneously combust. My 3.8L supercharged engine has a compression ratio of 8.5:1. The standard 3.8L has a compression ratio of 9.4:1. Now here's the trick: running at no boost is safe with regular. Once I start to boost, it increases the compression and to make matters worse, the supercharger heats up the air because it compresses air in its housing. If I floor it with regular gas, I WILL cause engine damage and adventually blow the engine because the heat from the compressed air in the supercharged and the heat generated from the engine will cause the gas to burn too quickly - more or less try to force the piston to travel in the opposite direction.

I'm sure people are also wondering "Why would premium give me worse performance?". Well the answer is that an unmodified stock engine will not be able to burn all the fuel that is in the cylinder because it will not be hot enough to do so. Your catalytic converter "should" burn off the rest but that is just a waste.

So, Compression = Performance. More compression = easier/quicker to burn gas. Gas burnt to quickly = blown engine. Higher Octane saves us from it.



I'm doing this while at working and jumping between this post and taking calls on my job so I hope I didn't drop the ball somewhere.

If you have any questions, please ask.

 

Thanks for clearing this up with an educated response. Hopefully all the Nay Sayers will listen that with a high performance engine, as a general rule of thumb REQUIRE premium gas.

Jason