I've got an '04 Hemi QC with 8,000 miles. For the first 5,000 miles to do the breakin well I ran it on mid-grade 89 octane. More recently, to save money on gas, I've been running it on regular 87 octane grade California gas (only $2.70 a gallon yesterday!). In most instances it runs fine with a minor change in performance, but, generally going uphill or under some acceleration at times I hear minor engine pinging. Has anyone tried using a bottle of octane boost at fill-up with 87 octane to get rid of this? I know some folks think octane boost is B.S. but if it works, on a fill up I'll still save a couple bucks a tank after buying the boost.

Given how minor the pinging is and that it doesn't occur that often I'm inclined to think it won't hurt the engine, but I'd rather not take chances.

 

DC has stated 87 is acceptible but 89 is preferred in the 5.7. I don't think you'll be hurting anything by trying the 87 with a bottle of octane boost -- just make sure your tank is full and you use a good-quality octane booster.

I honestly don't think you'll be saving any money though.

 

Octane Gasoline changes the charachteristics of the fuel. Heptane is what "regular" fuel is made of. It is more explosive than Octane. The higher the Octane number (up to 100) the higher the percentage of Octane Gasoline mixer to the Heptane Gasoline. The higher the number, the less explosive the fuel is. That's why you get the pinging with lower octane (the fuel is literally exploding sometimes before the spark).

If your truck is detonating (pinging) or has pre-ignition (fuel exploding before the spark) then use the higher octane fuel. If it costs $.10 per gallon and you have a 26 or 34 gallon tank, it will cost you $2.60 to $3.40 to use the higher octane fuel. Where can you buy Octane Booster for less than that?

I have been using 87 octane fuel in my 2003 Hemi in Phoenix including towing with no pingin whatsoever.

 

I use 87 without pinging as well, but if your's in pinging you need to run the higher octane.

It's my understanding pinging WILL hurt the engine.

Effects of Detonation
Other than running an engine without oil, there is probably nothing that you can do that is more detrimental to an engine than detonating it. In an ideal combustion cycle there is a controlled burning of the compressed fuel and air, but during detonation there is an exploding of the mixture with a instantaneous release of all its energy, regardless of where the piston is in its stroke. The timing of the auto-ignition will have a direct effect on where the damage takes place.

Detonation very early in the compression stroke is usually the silent killer that goes unheard by the driver. This form of combustion usually results in rotating assembly failure by attacking the connecting rods and bearings. Detonation that comes nearer to TDC or slightly after is usually heard as pinging and will likely result in the burning of the piston or the lifting of the ring land from the piston. The force from the colliding of the multiple flame fronts can be likened to the wake of two boats travelling in opposite directions on a lake. When the two wakes meet, they usually peak and absorb the energy of each other. The more dominant wake will still have some leftover energy and will proceed weakly in its original direction. The same holds true for colliding flame fronts in a cylinder. If you have one flame initiated at the spark plug and another started independently of the plug, usually the spark-initiated front is the dominant one. As the two flame fronts collide, the pressure in the cylinder rises from the compacting of the molecules. Historically, the normal flame front has enough energy to run over the abnormal one but uses a lot of its energy to do this. Add to this that the abnormal combustion has consumed a portion of the combustible mixture that filled the cylinder, and the least result is a loss of power, if not a damaged engine.

http://zhome.com/ZCMnL/PICS/detonation/detonation.html

 

I agree with DonG - pinging (if it's detonation) slowly destroys your engine.

I was at Walmart and checked the price for STP Octane boost. The price was $2.37+tax. It is supposed to be added to 15 gallons. 89 Octane for 15 gallons is $1.50 more than 87 usually. Use 89 if your truck pings at 87 octane, otherwise 87 works as well as higher Octane.

This raises one additional point. If your truck pings at 89, get it checked out. It shouldn't. Until you get it checked use premium octane till you get the detonation taken care of. I might consider trying a different gas station as well.

Unless it's a diesel, it shouldn't be rattling.

 

I remember reading about some fuel additives are harmful to the HEMI. I cant remember for sure what it was (MTB) or something. I don't have my truck with me here at work today or I'd go read the owner's manual and find it. Look at the owners manual and find out. I remember the dealer pointing this out to me when I bought it.

 

You're better off with just getting the midgrade gas like everyone is saying. Stay away from the boosters. Some are even simple industrial solvents that could harm parts of the fuel system.

 

This is for Jeff 17,Jeff ,I don't know where you get your information about using heptane ,but you couldn't get any worst of an answer then to use heptane. First try to find it. Heptane is Made By Phillips Petro.They make certified test fuel for Knock test engines. Heptane by it self has a zero octane rating. That means that it will knock in almost all fuels. It is used to lower test fuels in Octane research. You can use as low as 85 octance if you live in Denver Colorado ,if you live in the mountain areas. On the sea levels you need at least 87. I ran an Octane testing Facility for a Major oil producer on the east coast for over ten years. I was known as Mr. Octane in the industry. And you can not use Heptane in an automobile engine and expect it not to knock. As for MTBE, That's the main octane booster in Gasoline. Some states don't like it because it gets into the drinking water and causes cancer. This is true but it's the cheapest answer to boost the octane since they remover lead. And lead is worse then MTBE.. If anyone has a problem with 87 octance tell your dealer and insist that they go over your engine carefully. Not two engine run the same most are close. I use 87 Sunoco in my 04 hemi with no problems. I know what's in there gas so I know that I will get the proformance that I need. Crown Fuels also makes a great gasoline. For some reason Chrysler engines have always run a little higher then 87 oct. Some times in my PT cruiser I will mix my gas. I'll put in three gallsons of 89 then the rest in 87. It doesn't bring it up much but it curses the problem. One other thing that you can do is by a six pack of stp fuel injector cleaner and if it pings add a bottle to your tank. Your engine is telling you that it needs help. As your engine gets older the need for a higher octane will increase. Then it's time to trade it off.