what are some major reasons for bad gas mileage? my car says

you need a tuneup/repair
you cant drive as good as whoever tested it
car companies like lying and it really isnt that good

all 3 can be true

specs on paper are based on 100% perfect environment. so expect 3-4 less

>>15135595
City driving? Driving like an ass? Check engine light?

check tires
airfilter
etc

bad plugs, bad coils, bad oil, not using the right rated gasoline, carbon buildup out of control, dirty air filter. something could also be wrong with the fuel pump.

Do a tune up. Get Plugs and Coils changed. Run fuel injector through, check to see if you're using the right rating for fuel (most use 87, but your car could be rated for 89), get an oil change and change the filter, and change the air filter.

If none of that does it, well there could be something else internally wrong with your vehicle.

>>15135620
>>15135608
false. i get over epa all the time. it's not common to get less than epa with good regular driving.

low tire pressure, heavy oil, poor compression, poor afr, poor timing, stuck or clogged pcv, dragging brakes, could be literally anything.

you could also be a shitty driver who treats the gas pedal like an on off switch.

>>15135608
>>15135620
it's a little more than 3 or 4 less though

>>15135633
no lights, city and highway. normal I'm not a speeder really

>>15135639
used car I just bought about two months ago.

it's almost 60k miles, so I should do a tune up?

>>15135775
>I just bought about two months ago.
What kind of car, engine, transmission?

>>15135784
Volvo c30, auto. runs great otherwise

>>15135790
lolvos are notoriously thirsty fuckers, even when you treat them nice and don't suffer from lead foot syndrome
t. vavlo owner

>>15135595
Shitty driving, lack of maintenance, shitty driving, low tire pressures, shitty driving, and dirty surfaces.
Pump your tires up, wash your car, fucking maintain that shit, and drive better.

Disengage emergency brake.

Remove all dead Tyrones from the back.

>>15135620
>specs on paper are based on 100% perfect environment. so expect 3-4 less

EU tests are, but not American EPA. EPA mileages are actually pretty realistic. I normally get 3 mpg better than EPA on my Mazda 3, and equal to EPA city.

http://www.greencarreports.com/news/1091877_why-european-gas-mileage-ratings-are-so-high--and-often-wrong

>>15135595
Poor posture while driving can lead to excessive throttle at the wrong time.

File: noriyaro_fd_rx7_newtype_tsukuba.jpg (211KB, 1024x683px) Image search: [Google]

211KB, 1024x683px

>>15135595
>what are some major reasons for bad gas mileage?
>my car says 23 city, 29 highway
>but I've been getting 14-16 on three tanks now

Remember that City driving is considered to be a mix of speeds. So if you are always in short distance stop and go traffic (go 2 or 3 blocks, then stop, repeat cycle) your mileage will suck. My new car is rated 24 city (yeah, kill me for having a guzzler new car with a lot of HP) but it only got 19 MPG. I adjusted my driving style for the new engine and it climbed to 19.8 MPG. Damn! But I have nothing but stop and go traffic and lots of slow driving on work commute (short distance).

What also killed my mileage were all the hills. I am constantly going up and down. One day, I was assigned elsewhere so I stayed in a nearby city. My mileage shot up to 25 MPG because there were few stops AND most roads were 35 MPH or better. So it exceeded EPA there since it was a level city (no hills).

I am back home and my mileage dropped back down to 20.2 MPH now with my semi-hypermiling driving. Double damn. I cannot truly hypermile because then all the other drivers will be totally pissed at me. My car is an ECO car too which stops the engine if I am stopped and press the brake pedal firmly. So even with that gas saving method (like in europe), my MPG sucks due to hills, slow speeds, and lots of stop and go.

Airplanes get good mileage for the fuel they use due to wings. Maybe I should install lots of fins and spoilers to improve my mileage? After all, my keychain strap says "Remove Before Flight".

>>15140081
>that key-ring thread reference

Shouldn't it be "Remove after flight"?