road trip- a few mpg questions

[transistor]

Im planing on taking a little road trip in a couple days.. I'm taking my grand am. I know this isn't a grand am board but I figure people here will know. ok, first off, is there any increase in mpg with premium fuel over, say, 87 octane? and does the air conditioning decrease the mpg? thanks

 

[leenjen]

no, your grand am is meant to run on 87 octane. some owners manuals even say that using premium unleaded will damage the engine. the higher the octane, the hotter it burns since the rating shows it's abliity to resist heat. this makes the combustion more controlable in high power/high compression engines. if you had a supercharged grand prix GTP, then premium would be fine.

 

[Big Poppa]

All engines are different. Mine gets much better acceleration and mileage w/ 89, but worse w/ 92 or 93. Your A/C will definately put a load on your engine, causing worse mileage. But down here I would give up a little MPG for some cool air.
Good Luck

 

[espnfreak]

isnt it like on american cars it runs directly off the engine the A/C? and that bogs it down, and on foreign cars it runs off a separate compressor? which doesnt take as much energy away from the engine? thats what i heard, and i believe it because our 95 camry has no difference in acceleration when i turn on/off the air, and my big boat explorer drags when i crank max a/c

 

[FitzMatt]

After 55 mph, your mpg being to decrease as your car is fighting more and more against wind resistance. The closer you drive to 55, the better mileage you are gonna get.

 

[Peter Weber]

Studies have shown that using A/C at highway speeds or driving with the windows down to get air into the cabin has about the same effect on mpg. Rolling down the windows causes more drag while running the A/C put more load on the engine.