I have had 2 GM trucks 6.2 liter engines, a 2015 GMC Sierra Denali and a 2019 GMC Sierra Denali Ulitimate and always ran 87 octane with no problems.
The truth about gasoline octane, a lot of the new car owners manuals will say that you have to have 94 octane which is a lie, if you believe this then you are just going into the game with half of the information, be realistic about your car.
The standard hip pocket rule of thumb for octane is if your motorcycle or car is not pre detonating then use the lowest octane available, octane to put it in gentleman's terms can be loosely called " The Resistance to Detonation of any fuel", and the best example I can give you is if you take a pie pan of gasoline that is 87 octane and a pie pan of gasoline that is 94 octane, you put them on the floor of your garage and you approach each one of them with a lit match, the 87 octane will detonate further away than the 94 octane, so gas is formulated to have a greater resistance to detonation the higher the number, and the number comes from an old thing that was called the "Anti Knock Index" because older cars over time would have the valves go out of adjustment, heads would leak, air would get into the motor.......and when the air would come in it would actually make your car run hotter, and to lower the temperatures in our cylinders we would put in higher octane gas, so if your car was knocking or running on after you turned the key off in the 50's, 60"s & 70's the solution for that was to put more expensive and higher octane gas in your tank.
Lead was always in gasoline back then as a lubricant, but they would use things like seetane and later on toluane and other octane modifiers, and these octane modifiers were put in to artificially pump the octane number up on what the regular chemical composition of gasoline would be.
Believe it or not one of the best octane boosters is water, and old trick used by old diesel mechanics, because of the hydrogen chain of water being H2O.....there is 2 hydrogens and 1 oxygen, if you have an old diesel engine that needs to have the heads cleaned, one of the Hail Maries was to spray some water through an atomizer bottle or spray bottle into the intake track of a diesel and what it would do is it would crank up the octane in the diesel fuel going in and it would burn out all of the carbon deposits inside the motor, but it is actually pretty dangerous and it can scatter a motor while your spraying it to explosive results.
Only use 87 octane fuel in your motor vehicles regardless of what the owners Manuel says, if you use any thing higher then the ethanol will chemically retard the timing of the engine which is actually alcohol poisoning.
Higher octane does not burn cleaner as the petroleum companies would have you believe.
It is not about the ethanol percentage because 94% octane does not contain more ethanol than 87% octane, it is about the ability to burn the gas versus the ethanol ratio in it.
Ethanol is hydroscopic meaning it brings in more moisture.
There are 2 methods of determining the octane number, one is the RON and the other is the MON, some countries use the RON exclusively and some countries use the MON exclusively. In the United States we use an average between the 2 numbers so the next time you are pumping gas for your car look at the pump and it will say 87 octane RM/2 and what that means is that there adding the research number R+M/2 to the mechanical number and they are dividing it by 2, so they are giving you an average between the RON number and the MON number, now when you are looking at your owners manual for your Japanese or European motor vehicle it is going to have a higher octane number and sometimes these manuals for cars specify a higher grade of gas because they have a higher cylinder compression and they are going to need 98 octane fuel, well 98 octane in the European system translates to our system in the United States to about 91 or 92 octane, so you are not buying the wrong gas and you are not going to damage your vehicle, the gas that is sold in Europe is the same gas that is sold here in the states they just have a different method of measuring the octane number.
Every company that makes their money selling additives have tested out fuel, so if you use 87 octane in your motor vehicle you will not get a single horsepower number higher on a dynamometer running 94 octane through your cars engine than you will running 87 octane it just does not work that way.
If you are going to over build your motor, if you are going to run a high compression motor, if you are going to alter the timing to fire that spark plug at a point where the piston is higher and therefore the fuel is under higher compression then you do have to start using a higher octane fuel or you will pre detonate, so simply put if you've got a tuned motor or if your motor is under a high heat high stress application then it is ok to run a higher octane fuel to help counter the effects of cylinder pressure and heat.
If you put a higher octane fuel in a motor that clearly does not need it you are doing your motor a disservice, and you are doing 2 things to it, 1 is you are making the oil companies really happy and we all know they need more money..... Right? But really what you are doing is chemically altering the timing of your engine, if you have points or fuel injection with a computer your spark is set to fire or go off at a certain time that is all based on the appropriate fuel for your vehicle and when you start changing the formulation of that and you start putting high octane fuel in then what you are doing is chemically retarding your timing because let's say now instead of that thing firing at 18 degrees before top dead center now in fact it is going to have to turn further, the crank will turn further, the pistons will go higher before it actually sets off the explosion because high octane gas has a greater resistance to detonation and compression, so now you have just messed with the timing of your vehicle.......spark will happen and ignition will happen but the time it takes because lower octane fuel burns hotter faster and higher octane burns slower and will take a longer amount of time before it lights up, spark and timing is the same but the flash over, the amount of time it takes to flash or fire up is changing and taking longer and is occurring later and that will give you the same effect as if you then further retarded your timing.
With the current junk fuels blends they are selling us there is 20% less gas in your gas today than there was 10 years ago, between oxygenation and ethanol MTBE and all these things that are in the fuel they are taking the place that gas used to be and as we did that a lot of these components and chemical recipes that are in your fuel are there to pump up the octane that we lost when we started putting ethanol and oxygen in the fuel, and now gas does not last anymore, it used to last a couple of years but now within 30, 60, 90 days it smells like varnish and the engines won't run right.
Modern fuels are literally just eating seals, the rubber is just falling apart, so if you are going to let's say rebuild your carbs make sure you are using rubber items and elements in your carbs that have not been sitting in a bag for 30 years because those things are not going to be safe for modern day fuels, use modern day "Viton" seals and rubber.
