Crappy Miles Per Gallon! WHY?
 

I drive about 90-95% highway at about 65 mph. on a full tank (not topping it off about 9.7 gallons) will get me about 250mile (when the gas light first turns on). when i first got my car i was gettin close to 300miles per tank. and ive noticed that its been goin down a lil more every month. i have about a 2" drop, stock wheels, no name intake, magnaflow catback, factory front end mask, esam wind deflectors, fab spoiler. any one know whats goin on im getting about 10mpg less then i should be. and its not gettin any better

Well some say when you get engine upgrades you gain HP and Gas mileage....guess what... they LIED! Remember the saying " For every action there is an equal or opposite reaction", Well this applies here. Give up MPG for HP. Now this is only on certian aspects....the exaust you loose some backpressure for HP this robbs you of the MPG. The intake should have counter acted this, however you are giving the motor more gas to fuel ratio and this takes away from the MPG as well.....these upgrades are ment for performance. If you have a Sound System...guess what....you got it...Amperage load puts a constraint on the alternator to charge up the battery which puts a minimal restraint on the motor...but still we are talking about a 1.5 liter engine..very small.....all those things in account ADD up. Eventualy you have to realize you pimped out your ride at a cost. I gave up a 2006 Mustang GT for the Scion XB and I have Gained so much more it the long run....Space, Gas Mileage, not to mention I can park my XB everywhere without ever worrying about a scratch....cause it's small...Compact. No worries Bro just hang in there Remember It beats walking.

None of the mods you listed should have effected your gas mileage like that. The basic power mods do not negatively effect your MPG. Driving your car harder because it has a little more power does. Your stereo can not put enough load on the alternator to reduce your MPG. You'd feel the car lose power every time you turned it up if that were true. Many of us would have to turn down the stereo to leave from a dead stop.

The things you need to look at are your driving style and maintenance/problems with the car. You spend most of your time at 60 - 65 on the highway which is about the best speed and situation for MPG in an XB but how do you get up to speed and how do you drive when you are not on the highway. Hard acceleration will eat up fuel in a hurry. You'll save a lot by taking a little time getting up to speed. If your commute is somewhat hilly and you are using cruise control, you'll use more fuel than you need to (I found this through personal experience).

Make sure you've done all the maintenance for the mileage on the car. Check your tire pressures. Is it time for new spark plugs or oil change?

That's all I can think of at the moment. Good luck!

If you want to measure you gas mileage with reasonable accuracy, you have to record the mileage between fill ups. Fill up the box and note the mileage, or reset a tripmeter to zero. Then take the the number of gallons at the next fill up and devide the gallons into the miles driven. And you must do this several times to lesson various errors. Noting how many miles you drive to the light goes on is not very accurate.

I have taken two highway trips of 150 miles round trip in the last week with my wife in the car. Speeds were from 65 to 75 MPH. I recorded almost exactly 28 mpg and don't expect to do much better.

it could be crappy winter gas

A good point if the poster lives in a part of the country that uses reformulated gas in the winter this could result in a fuel mileage drop.

I've heard of differences but could it be 10 MPG difference???

thanks guy very helpful. i do drive...how can you say this...like a granny..hahha...i didnt do those mods to go faster....just for the sound....if i wanted to go fast the xb would of the last car of choice....dam echo motor! hahah....well ill keep on tracking the mpg and ive never checked my tires so ill do that as well....let hope its crappy gas!

Robot Box, where do you live? I am asking because I live in MN and right now we are in the middle of a cold snap. In every vehicle I have ever owned the milage gets worse when it is 10 or colder out. My last fill up I got 29 to the gallon, I usually get 32-33. Ethonol in the gas kills milage also.

also could be how u drive now that the car has some modifications on it...i know when i put an intake on my car i could resist getting on it sometimes just to hear the sound..and i imagine it is only going to get worse when i put my headers and exhaust on...but the mods will mess with your a/f ratio (ecm is always learning and adjusting) plus all the facts listed could cause a problem with mpg but 10 mpg sounds like alot because with my aveo i should be getting 30 mpg but i have a broken o2 sensor, heavier wheels, and i get on the gas alot plus its an auto trans and when i calculated the mpg last week it was 24.(something)....so its odd that you dont have something else wrong thaat would cause a CEL

Have you cleaned your AIS/MAF?

It is only slightly more difficult then changing a fuse and should be done everytime you change your air filter or once a year.

i live in oregon

i got the mods done pretty much right after i got the car new. i think i got it last june. and it just seems to be getting less and less mpg

10 mpg drop? ummm sure... if you were actually getting 35mpg i have no idea why , lol.

hp improvements do not make you lose power. too large or too restrictive of an exhaust and THAT will hurt mileage.

it's probably a problem regarding your right foot.

crappy miles per gallon, why.
 

With the winter blend fuel around here, I loose 2-3 mpg. It always comes back when we get summer blend fuel.

How many miles since a new air filter?? Clogging air filter will cause a progressive drop in mpg.

hmm for got all about the filer. im running up just about 10k on it

i hardly take my car over 4k rpms

your air filter should still be fine. if i were you i would just do a mini-tune up though. new air filter, spark plugs, and an oil change and put in a good actual 100% synthetic oil like AMSOIL. see if it gets better then :-)

the manual says it doesnt need spark plugs for 100k, and our motors get better gas milage between 3500 and 4k, could be low tires, the road, the gas(not just winter blend but water in the gas) the way you drive