Quote:
Originally Posted by arcosine
My Saturn get better mpg with premium because the timing retards with lower octane... though premium is peppier.
|
Quote:
Originally Posted by 19bonestock88
Maybe I should try some 91 in my Ion? I didn’t think that normal “low performance” cars would benefit much...
|
Most people wouldn't get much better fuel mileage from more octane because most people do most of their driving at low engine loads. At low engine loads you're restricting the air and causing less compression and therefore less heat. Also less fuel is used. It's basically the same reason you can use less octane at higher altitudes. When I had the digitally adjustable distributor on my air-cooled Beetle it was impossible to get the engine to ping at low cruising loads, regardless of timing. Basically advancing it up to a point caused power and efficiency to increase, and going over that it just caused that power and efficiency to decrease. Detonation protection is mainly needed at or near full throttle where you're compressing more air and burning more fuel, both of which cause more heat. And that heat can cause unburned fuel to want to detonate.
But if you're like me and have mostly steep mountain passes to climb or you pulse and glide (use high loads then let the car coast) then octane is going to make a bigger difference.
But in my opinion, whether you see a difference in fuel mileage or timing retarding at any load by changing the octane, you really should use the higher octane. What if the knock sensor malfunctions and your ECU doesn't detect that the fault and the engine starts pinging like crazy. Then next thing you know you could be out of an engine.
Quote:
Originally Posted by redpoint5
All water in the filter would do is restrict the airflow. Don't think it would cool the air because air wouldn't flow through the wet portion. If it did flow through the wet portion, it would quickly become dry.
|
A restriction would decrease the need for octane.