Gas mileage drop halfway through a tank?

[bash1979]

Hey folks,Just wondering if anyone has experienced a big drop in gas mileage for the 2nd half of a tank?My Vibe has consistenly gotten ~300Km from fill-up until the halfway point. So you would think that projects to ~600Km for a full tank, right? Nope! I'm averaging maybe 150-180 Km from the halfway point until the light goes on!! I'm now thinking of resorting to filling up the Vibe at the halfway point to maximize gas mileage!! Just wondering if anyone else has seen this...Thanks!

[Baltovibe]

Probably because the fuel gauge's action is non-linear. Mine tends to stay above the Full mark for a while, then starts dropping more rapidly towards empty.

[BOZACK]

My gage drops faster after the half mark also. It then slows again toward the quarter mark. In the more thanhalf dozen cars i have owned all have had gas gages that were not accurate.

[djpositivek]

My Vibe doesn't seem to be too bad but other cars I've had were like that. Would seem as if you were going to get crazy mileage but then the needle drops down quick on the second half. What model Vibe do you have ? I'm getting around 600 kms to a tank but mine is base FWD and under 2 weeks old.

[bash1979]

Thanks for the responses.I have a base FWD, automatic....approx. 2 months old. I expected the gas mileage to get better, but unfortunately, it's gotten worse. I got over 615km on my first tank, but haven't come close since. I just hit 5000Km, so I'm due for an oil change. I'm hoping that helps!

[Mavrik]

hey fellow canadian.My Vibe I can usually get more km on the top half of the fuel tank then I can at half and under. Plus the bottom half of the fuel tank is a little smaller then the top half so I was told. On average I get 600 km per tank. 400km of that is usually to the half way mark.I'd say yours is acting normal.Now what you will notice... or at least I have... every gas pump shuts off at the "full" mark at a different amount in the tank. Personally for me I like to use self serve and fill it right up to the point of almost spilling out. On city driving I average 550-600km per tank but I know I have gotten 700+ roughly on a full tank highway driving. Colder weather... not sure what its like in ottawa right now... that will make your mileage drop slightly as well.

[bash1979]

Wow, 400km to the halfway mark...I'd love to see that on my car!! Nice job! Good point about filling up the tank....I always stop pumping after the auto-shutoff. I just figure if the pump says it's time to stop, it's time to stop! But maybe i'll try to squeeze in a few more litres next time and see what happens.Thanks!

[Mavrik]

Its not a tried tested and true method because every pump is a little different, but I've managed to squeeze in 4-6 more litres into the tank after the pump clicked off at auto full.When I drove across canada, I filled that right to the fuel cap lol... was easy to get 400 before half a tank... but then 300 at most for the lower half lol.

[AKLGT]

yes in the vibe, you can squeeze out quite a bit more into the tank. i found out that does not work in my LGT however and made quite a mess.

[Mavrik]

also with the LGT... it must never be overfilled as the vent valves in the evap system will fill with fuel, set an engine light for emissions code, leak detected or along that line... and no warranty on repairs if found completely logged up with fuel from over-fillinf.

[tangerine]

bottom half of the tank is always smaller.