Why am I burning so much gas?

Question

I changed my oil yesterday and put the correct amount of air into my tires (35lbs of pressure) and today I'm burning more gas than yesterday. Aren't doing those things supposed to improve gas mileage? Why suddenly did I go from being able to go 350 miles on 25 gallons to 200 miles? I checked it while I was driving. I went 50 miles with a quarter of a tank. My truck holds 25 gallons. I divided that by four and I got 6.25 gallons which would put me at roughly 8 miles a gallon when before I got 14 miles per gallon. Please help me! No one else knows what's wrong!

Answer 1

when you changed the oil did you change the air filter? that is what actually helps with gas mileage.

The only other thing I can think of is if you are carrying a heavier load now, have you added something to the car carrying extra cargo or anything different?

if it's neither of those then I don't know what to tell you except that maybe you miscalculated before.

Answer 2

Not exactly sure. You didn't put the make and model.
You might have knocked off or detached something when you did the oil change. I can't think of anything under the car that you could have knocked off unless you did it taking the oil filter off.
But look around the valve cover and make sure you didn't accidentally knock off a vacuum hose. Like the PVC hose or erg vacuum hose. even if you didn't knock them off but bumped them and caused a vacuum leak could cause a fuel mileage loss.
And never go with what the Gage tells you. i can go 200 miles on the 1st half tank and only get 100 miles more out of the other half.
the way you figure out your mileage is...Fill your tank up. Write down the amount of gallons you put in it. Hit your trip meter if you have one and reset it to 000miles. Drive your vehicle "what ever it is" and then when you need gas, Fill it up again and see how many gallons you put in it this time. Then divide the miles you went with the with the gallons used and you'll have your approximate gas mileage.
Trust me don't do the 1/4 tank times 4 thing! It doesn't work like that! Gages aren't that accurate through the whole range from full to empty!

Answer 3

My first thought is, don't rely on the gas gauge, as they are notoriously unreliable, most especially for determining gas mileage. For a true reading, use the trip meter, and next time you fill up, divide the amount of gas to fill up into miles driven.

Also, how about your driving style? Have you been riding it any harder than usual? Have you done anything like off-roading or towing that would cause it to use more gas? Often times I find that the best mod for gas mileage is the guy on the go-pedal.

Next, check your O2 sensor. If it's dirty or has ~80K or more miles on it, you should consider cleaning or replacing it, respectively. Then there's the usual stuff like air filters, plugs, and distributor cap/rotor. Even outside temperature and winter blend fuels could detract. It's a process of elimination, more or less.

Answer 4

Most fuel gages are not accurate ways to tell how much fuel was burned. Top off the tank and drive 50 miles or a set amount. Refill tank and use how many gallons it took to figure out accurately. If you want some gas saving tips see the SAVE GAS section here http://painintheexhaust.blogspot.com

Answer 5

Like the other person answered, check the air filter, also, if you have the check engine light on, get that checked out too. Bad O2 sensors will cause your gas mileage to go downhill quick. Also, what junk are you carrying? If allot, and not needed, then get it out of there. More weight, will lead to less gas mileage too. Also driving habits, and braking, and such. Then there is that infamous winter gas formula the fuel companies do for winter. That drops gas mileage too. Good luck, getting to the bottom of this.

Answer 6

Were you carrying a lot of weight?? Dumb question but who knows.. First, I can think of nothing that would make such a radical change...With one exception......Did you by any chance knock the wire off of the computer temprature sensor??? Don't know what this thing is Make, Model, year engine size, transmission. In t5he mountains, desert. Go with the computer temp. sensor first.. The light/gauge temp. sensor has one wire plug on it..The comp.temp Sensor has a two wire plug on it.... If the temp. sensor is kocked of on a computer operated engine the comp. senses a cold engine and supplies way to much fuel to the hot engine..See ya

Answer 7

where do you live. if its cold outside your car burns more gas because the cold air is mixing with the gas and is burning better so your getting more power which in fact burns more gas. also you should try changing/checking your spark plugs, spark plug wires, oil filter, air filter, fuel pump, fuel injectors, get your tires rotated and balanced. it could be all of these things but that's all i can think of right now. hopefully this will help.

Answer 8

well ya didnt say what make/model/yr etc of the vehicle, but take a stab at this, check your exhaust muffler.if its clogged itll give ya the same symptoms you mentioned,itll seem like its making good power,but gas mileage sucks.my dakota had a clogged muffler and i got pretty much same mileage.eventually my muffler started falling apart, and i found out the friggin thing had a clog. it was a chance discovery as i had new plugs,clean k&n filter etc, a new one can run as low as 20 bucks.so go ahead and replace it you can do it yourself and see if that helps

Answer 9

Did you put the right weight oil in it?

Did you knock one of the hoses loose? A vacuum leak will kill your mileage.

M

Answer 10

tune up might help maybe your getting bad spark pluggs and wires..also check to make sure you didnt knock off any wires to anything electronic when you changed the oil..