Decreasing Mpg :'( - Toyota Nation Forum : Toyota Car and Truck Forums

Manny1337 · 12-31-2009, 12:42 AM

As the title states ive seemed to loose mpg. I was at about 28 and now i usually get around 22ish. Same driving nothing extra in car. Could it be the o2 sensor or bad plugs? i haven't gotten around to checking the plugs yet because its pretty cold up here. Any typical reason this would happen? No check engine no problems with her at all.

Judd sandage · 12-31-2009, 01:42 AM

I would check your trans (assuming that its an auto), while driving do you notice that it runs at a higher RPM then before? check to make sure that o/d is turned on, with it off you don't get cruising gear and hence lower gas mileage.

uibalnme · 12-31-2009, 02:33 AM

When's the last time you checked your tire pressure?

Stillrunning · 12-31-2009, 05:36 AM

Using gas with ethanol will reduce mileage by at least 10%. So much for the cheaper price.

islandboy57 · 12-31-2009, 05:59 AM

Yeah, a winter gasoline blend with Ethanol could be the culprit.. Next I'd check your tires and air filter.

Manny1337 · 12-31-2009, 10:13 AM

Well the trans isnt driving in any higher rpm and od is kept off. its not the gas because it just started doing this (its been winter for a little bit) and i check my tire pressure every week, anything else? =P

edit: and the air filter is clean checked it the other day

The international · 12-31-2009, 10:33 AM

checked compression?

Manny1337 · 12-31-2009, 10:47 AM

nope i have not, do not know how nor do i have the tools =P.

i just pulled one of the spark plugs to check it there was corrosion all on it. im assuming thats not too great of a sign. i put the plugs in last year they are bosh platinum =(

The international · 12-31-2009, 11:11 AM

Go to the repair shop 'cause I don't know either

. Though maybe this can help you http://www.automedia.com/Checking_Co...ht20020701cr/1

yotatoter · 12-31-2009, 05:26 PM

the mileage sometimes decreases in the winter ,not sure why other than poor gas or engine temp. not running as hot

the_professional · 12-31-2009, 05:47 PM

I'd really get rid of the BOSCH plugs when you can.

BOSCH is shit in our cars, and they are known to fail prematurely. I would just bite the bullet, get rid of them & get some NGKs.

csaxon · 12-31-2009, 07:24 PM

02 sensors begin to lose efficiency around 100K miles and that effects gas mileage.

Judd sandage · 12-31-2009, 07:42 PM

well, if you do a lot of highway driving I would recommend to turn on OD as that allows the rpms to drop for cruising. better gas mileage that way.

Stillrunning · 01-01-2010, 06:41 AM

Unless the engine is missing I doubt plugs or wires. Either the spark lites the fuel or it does not. Longer heat-up times during winter will consume more fuel, but once the engine is hot you should get same mileage - more so because you're not using A/C. If you know how you could test the o2 sensor and the ECT (engine coolant temp sensor). A small investment in a Haynes Manual would show you how, and save you some money. Compression test might help but without an earlier base measurement you won't know if it's degraded and by how much. Slightly grabbing brake will also reduce mileage - check wheels for difference in heat. Other than that you'll need to take it to a mechanic as you'll spend money on unnessessary parts taking guessed suggestions from us - we aren't psychics.

Frodo65 · 01-01-2010, 11:55 AM

Quote:

Originally Posted by Manny1337

As the title states ive seemed to loose mpg. I was at about 28 and now i usually get around 22ish. Same driving nothing extra in car. Could it be the o2 sensor or bad plugs? i haven't gotten around to checking the plugs yet because its pretty cold up here. Any typical reason this would happen? No check engine no problems with her at all.

Are you one of those 'brilliant' folks with remote start? Doing more 'warm-up' idling, like to defrost the windows? These factors would kill the MPG by themselves - idling engines get 0 MPG.

One 'semi-normal' thing, made worse by cold weather, could be a thermostat that's a bit off, and opening sooner (or not closing completely). This would keep the engine from getting to normal temp as soon as it should, and cause it to burn more fuel. The semi-normal part is that thermostats do age, and can stick open (or closed) as they do...

I'd recommend a OBD scan gauge to keep an eye on various engine parameters as the car is running. You can find one for $100 or so. There are a number of scan gauges/OBD readers on Amazon and stores like Harbor Freight. Note that unlike a simple code reader, the scan gauge lets you monitor the data stream in the ECU, even when no DTC is stored. This lets you see things like a 'lazy' O2 sensor or an 'off' TPS or MAP sensor.