Posted: Apr 21 2005 at 1:22am | IP Logged

I was curious if anyone knows the differences in mileage using different grades of octane.  I have a 05 LE CC Titan and i currently average about 12.5 mpg on my first two fills with 87 octane (regular) gas, driving an even amount of hwy and city miles. 

Appreciate the inputs...thanx

Posted: Apr 21 2005 at 2:31pm | IP Logged

Thanks for the info...i was just wondering if the higher octane gas (92) would get better gas mileage.  

Posted: Apr 21 2005 at 7:29pm | IP Logged

Well if you use a higher octane gas then you must ensure that all the fuel is being burned. I understand that the higher the octane then the harder it is to burn, besides with todays gas prices being so high I dont think that the higher octane gas is cost effective. Even if it extends your mpgs by 2-4 mpg it still isnt worth the 2.25 per gallon of premium.

Posted: Apr 22 2005 at 4:54pm | IP Logged

Mavryck is absolutely CORRECT!  Adding octane to gasoline increases the compression level at which detonation occurs.  Predetonation is ignition of the air fuel mixture prior to the spark actually igniting it.  When compressed enough an air fuel mixture will explode on its own without the help of a spark.  Higher compression engines require higher octane ratings because they are compressing the air fuel mixture more.  Predetonation is horrible for an engine as the forces of the fuel ignition are hitting the piston before they are supposed to. 

That said, your Titan motor is more likely to generate LESS horsepower using high octane gas than regular.  Yea, that's right.  The fuel mixture in the lower octane gas will have a more complete combustion than the higher octane fuel and deliver more power.  Unless you're running a high compression engine, like I was with my supercharged Frontier, you're not doing your vehicle any favors by paying extra for high octane fuel.