A change in octane rating???

[Compaq888]

I have for the longest time refueled my car with 91. When the prices were $3+ I switched to 89. So far I'm refueling with 89. My car is designed to work on 87 octane but i'm scared my engine won't work as good in performance and the fuel economy will go bad. What do you think I should do?

87 is regular right??

Here are my car specs... http://www.nissannews.com/site_library/nissan/1999vehicles/altima/specs.shtml

Also I heard altitude has something to do with the octane too. I'm at 0 altitude.

And the cylender compression ratio is suppose to be 178 for all cylenders while mine are all 190. Having higher cylender compression builds up artificial compression requiring higher octane fuel.

[SVOboy]

Dude, 87 is what you want, putting in a higher octane than is necessary will hurt power and mpg. It takes the fuel longer to burn, but your car is not timed properly for it, so it ends up going through the 87 octane burn process and not finishing with all the 89 or 91 stuff.

[rh77]

Originally Posted by SVOboy

Dude, 87 is what you want, putting in a higher octane than is necessary will hurt power and mpg. It takes the fuel longer to burn, but your car is not timed properly for it, so it ends up going through the 87 octane burn process and not finishing with all the 89 or 91 stuff.

Yeah, I second that. If the car's designed for 87, that's all it needs. If you're worried about the quality of fuel, it's all the same gasoline at the oil company's mixing station until they add components to meet local requirements, octane components, and detergents. "Premium" fuel may have more detergents, which, IMHO, isn't worth the extra money at the pump. Just clean the fuel sytem, intake, and combusion chambers regularly (like before oil changes) with an additive (I've recently discovered "Seafoam"). You'll save a lot of $$$.

RH77

[Matt Timion]

I third that.

I would put some 87 octane in your car and if it starts pinging you can always put 89 in there.

As it is now you are wasting money and fuel by using too high of octane.

In my altitude (4000 feet) I can use 85 octane. Yay for me.

[Compaq888]

I will use the 87 from now on. What's ironic is using a hydrogen generator will make a better complete burn and give me the results as if I'm using 87 octane. 87 octane with hydrogen will give such a good boost in mileage.

We shall see in 400 miles.

[rh77]

Originally Posted by Compaq888

I will use the 87 from now on. What's ironic is using a hydrogen generator will make a better complete burn and give me the results as if I'm using 87 octane. 87 octane with hydrogen will give such a good boost in mileage.

We shall see in 400 miles.

I'm excited to see some real results from a hydrogen generator system (and its safety). Keep us posted...

RH77

[Compaq888]

Don't worry, even if there are no gains in the electrolysis method my unit can be converted for chemical method in less than a minute. I can use the chemical method on the freeway only and still bump up my overall mileage.

[CosmicMC]

I have to disagree on one point. There is no difference in the "speed" with which any particular gasoline burns based solely on the octane rating. It all burns at the same rate. Octane only refers to the ability of that gasoline to resist knock. Nothing else. Since there is no such thing as "pure gas" sold at an automotive gas station in the US, it is possible that manufacturers use different formulations between octane grades, and that might involve a change in the amount of alcohol, MTBE, or the like in the mix. You can't tell from the octane rating, though.

In a car that's engineered for 87 octane gas, you can use anything 87 or higher without a problem, but it's a complete waste of money. You will get almost no benefits, and what little you might get you will never be able to notice or quantify in any meaningful way.

[Matt Timion]

Originally Posted by CosmicMC

I have to disagree on one point. There is no difference in the "speed" with which any particular gasoline burns based solely on the octane rating. It all burns at the same rate. Octane only refers to the ability of that gasoline to resist knock. Nothing else. Since there is no such thing as "pure gas" sold at an automotive gas station in the US, it is possible that manufacturers use different formulations between octane grades, and that might involve a change in the amount of alcohol, MTBE, or the like in the mix. You can't tell from the octane rating, though.

In a car that's engineered for 87 octane gas, you can use anything 87 or higher without a problem, but it's a complete waste of money. You will get almost no benefits, and what little you might get you will never be able to notice or quantify in any meaningful way.

Looks like you're right. I was misinformed. I guess taking everything those guys at honda-tech say as gospel is not a good idea.


About Octane 1

About Octane 2

A very good read about high octane.

[Compaq888]

It won't hurt me to switch to 87 anyway.