I have a 04 w/ 115k on the clock. At 99k, I did all the maintenance that I could think of. I did the plugs and all the fluids. I have always run premium and nothing else. On average, I could've gotten 150-160 miles when the fuel gauge was at the half way point, now all the sudden its averaging 100-110 maybe on a good day. It doesnt have any CELs on or anything so I have no clue what it could be. One thing I did notice the other day is the hose on my stock intake box is cracked open right by the throttle body. I was thinking that it might due to that but wasnt sure. I was thinking that it was feeding in more air and maybe somehow it is running rich w/o throwing a code. Any thoughts or suggestions? TIA

 

basing your perceived MPG on the halfway mark of your fuel gauge is going to be incredibly inaccurate.

take the mileage you've driven since you've last filled up and divide by the number of gallons you put in when you refill

 

I have done that, and I usually averaged with 95% city driving about 22.6 mpg but now its right around 20.1 mpg. I was thinking maybe it has something to do with the "winter" fuel mixture although its only November.

 

you're probably spot on with the changes in gasoline quality there...

 

yep, my S and my GSR get shitty mileage on the "winter" blend

 

Are there any additives to help with this? I have heard good things about BG 44k but at $25 bucks/bottle, I'm not sure it would be worth it.

 

Spending that on the snake oil additive doesn't pencil, even if it did work. If mpg occurs to you at all while driving your S, it's time to trade it in for a prius aka give up on life. I'm actually hoping to get lower and lower mpg, since the lower it is, the more fun I had.

 

Okay, your post is idiotic. I'm not complaining about the mpg being so low. I do drive the car as if it was meant to be driven. It’s seen a few autox events. I just want to know what would cause it ie a part failure. If that is the case, I want to get to the root of the situation and replace it so the car can run more efficiently. Thanks for your opinion though.

 

fix the broken hose and go from there.

also, the additives DO help mpg - I can totally attest to it, just get a a good brand, not those cheapy ones - they might make it worse.

also, check tires for proper inflation, check spark plugs, and change oil. that should bring you right back to the same mpg.

if it doesnt, im gonig to bet that your catalytic convertor is on its way out.

 

you've been using that 75/140 diff oil, haven't ya.....j/k