My teg normally gets 260-270 miles to each tank of gas. This last tank, I only got 200, and this tank I am down to half, and only at 100. Why is my mileage going down so bad? I drive the same way all the time. I shift at about 3500 rpm for every gear. My dad said the spark plugs are probably going bad. Is this true, or could it be something else? Thanks.

 

bad plugs wont cause that much of a drop in mileage, but you could check them anyway.
with that kind of drop, it sounds more like you have a leaking injector or something along those lines, check the fuel lines, do you smell any fuel while driving or after you have parked?
you could try a fuel system cleaner ( i recommend techron, made by chevron) just to see if it helps, if it doesnt then most likely you have a leak.
but before all this check the plugs and see how they are.

 

yea i'd inspect all your fuel and ignition parts like the plugs and the injectors and the fuel lines to check for any signs of problems... have you done any work to your car recently? and when was the last time u gave ur car a good tuneup?

 

As pdcdragon said, when's the last time you gave your car a tuneup?. Here are some parts to look at:
1)Fuel filter
2) Air filter
3)distributor Cap and rotor
4)Spark plugs and wires
5) Tire pressure

 

i would say tune up as well, but ive noticed something about my teg when i fill up on gas sometimes it doesnt fill all the way up leaving me around 200 miles per the tank too. But when it does fill all the way up i get around 270 per tank. Its like "what the tanks is full and i only put 8.5 gallons in on a empty tank" werid. but yeah thats something ive notice about my teg.

 

I haven't done any tune-ups since I bought it in Nov. My tire pressure is exact. The dealership said I don't need any tuneups till 42,500 miles, and I'm only at 41,100. So I don't know. Oh, and I don't smell any gas at all or anything bad.

 

you might need to let the gas cap off for a few minutes to let the fuel indicator recalibarate itself

 

I passed 50k on a road trip that was 1800 miles long. I still get 300 mpg. Havent had a tuneup since I bought it....not sure if the previous owner tuned it like he said or not since I havent requested the history printout yet.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IntegraBoy04 &raquo;</TD></TR><TR><TD CLASS="quote">I haven't done any tune-ups since I bought it in Nov. My tire pressure is exact. The dealership said I don't need any tuneups till 42,500 miles, and I'm only at 41,100. So I don't know. Oh, and I don't smell any gas at all or anything bad. </TD></TR></TABLE>

Tune up at 42,000 believe me if you take it in at the mark your probably just wasting your money...because dont wont do anything to your car. check fluids oil change blah blah blah. Your call tho..sinc eits your car.

With my car i notice somtimes they my gas millage sucks right after i change the oil....who knows.

Check your fuel filter, air filter,plugs and see how and were you have been driving. example freeway or city.

You might have just had a heavy foot this last fill up and driving more aggresivly than normal.

good luck

 

i get about 315 miles on a full tank and my car has 116,000 miles on it. tire pressure and a clean fuel filter helps in my opinion. o yah its always good to put fuel injector cleaner once in awhile(i do it when i do an oil change) I recommend the chevron fuel system cleaner, it works the best for me so far. hope that helps

 

Ive had a similar problem lately, suprisingly enough its right after I installed my fuel preasure regulator (doh I think it might not be tight enough)

it might also be because I have a head gasket failure cause im burning and leaking oil and burning coolant

Edit:
I drive the hell out of my GSR, and before all of this I got 20city and 40highway

now it looks like im headed down to either the 12-15 mpg from the truck or the 4-8mpg from my SS lol

 

Anything else?

 

I usually get about 250-265 miles out of a tank. I recently put back on my stock alloys and i'm getting slightly better milage. Skinnier rubber made the difference. As said above, tire pressure can make you use more gas.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VoltageBlue01 &raquo;</TD></TR><TR><TD CLASS="quote">you might need to let the gas cap off for a few minutes to let the fuel indicator recalibarate itself</TD></TR></TABLE>
Can you explain how this works?