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I have a 96 XLT and I use premium in all my cars. My friend told me that in american V8's they love Regular b/c premium leaves carbon deposits on american V8's.
yo Alpine,
We have a 96 Bronco 5.0 and use 87 octane with good results (15 mpg overall). Once used prem. when fav station was out of reg 87 and CEL lit off (gas cap was tight btw). Ford tech said this sometime happens when using Prem. Does your CEL ever light off?
If you're not experiencing preignition (spark knock, pinging) with 87 octane gas, for example, then you don't need to run a higher octane gas.
I know that you'll hear people say that their car runs better, or it's more responsive, or what have you, with a higher octane fuel. From an engineering point of view, octane is an ignition retardant, and nothing more.
They need octane in gas because unlike diesel fuel, gasoline is more volatile, and octane is decent way to control the volatility as the pressure and temperature rise in the combustion chamber. When your car is pinging, the air/fuel mixture is igniting before the spark plug fires. Then the spark plug fires, and as the two flame fronts advance across the top of the piston, they collide. The noise you hear is from the piston slapping against one side of the cylinder from this force. Usually, engines with bad spark knock are on their way out.
Hope this helps.
Dan
Carbon deposits due to premium, thats a new one. Anyway, even the oil companies will admit, when pushed, that a higher octane than required in the owners manual is just a waste of money. Chevron used to put more detergent in the premium grade, but not any more.
Some engine designs will accumulate more carbon than others. The 2.9 in my old ranger needed a shot of Techron annually to stop pinging.
I use to run high octane fuel in my cars as well (mostly imports). But with my 93 Bronco 5.8L I found no advantage. In fact I found that running the higher octane I got 10-11 miles to the gallon in the city. Running 87 octane I got 13-14 in the city. Consumer reports did an article on this a while back and confirmed that using a higher octane than recommended in your owners manual has no long term advantage.