bad gas mileage Q...
 

So I just bought a 96 Runner with 150K on it (no lift or anything after market). I did the gas mileage figuring today. I'm getting 12.5 MPG. That is far less than the average from what I am reading people are getting here.

What are some things to look at to help improve this? Other than the obvious tune up (plugs, wires, fuel filter etc...) Is there anything 3rd gens are known for in this area?

I read about maybe a bad/blocked CAT. Is there a way to test this?

Thanks!

What kind of driving do you do (city, highway. If both, give percentage)? How are you figuring the MPG?

To test the cat youd simply pull it off and look through it....

Air filter as well as what you mentioned...
Is there an ECT button on third gens...?
manual or auto...?


:dj:

3.4L, auto, ECT is off, right now 70/30 city/highway...

I filled it up and reset trip. Waited untill about half a tank was used. Filled it again. miles gone between fill up divided by gallons needed to re-fill...

What size tires does it have...Larger then factory ?

:dj:

stock size w/16" rims...

Do you know when the last time a tune up was done? Do that first and see what you get. If that doesnt work alot of guys speak highly of using seafoam...me personally dont like disconnecting a vaccum source so seafoam can get sucked into the engine. I like using Auto-Rx, checkout my sig for more info.

My truck gets 22-23 during the summer months and 19-20 during the winter months.

your tune-up will probably help a lot, i get around 17 with 265/75/15 tires and nothing has been done to it recently except spark plugs

on my 95 runner the vacum was disconnected slightly and that made a huge diffrence and everything being sealed well like you said in a tune up.

air pressure in the tires is another mpg killer.

possible dirty injectors? does it run fine, just bad mileage? along with your tuneup run some injector cleaner and if you seafoam it (which i highly recommend) be sure to remove you O2 sensors. i found that if the exhaust is hot its easier to unscrew them

Remove the 02 sensors?? You mean just for the seafoam cleaning? Is that necessary?

my mpg's improved from 16 to 18 after seafoam in the tank.

i get about 280-300 on 15 gallons refill. 50/50 city/hwy

check the airfilter?

also clean engine oil. check the diff oil?

start with seafoam, drive 2 tanks and see if it gets better

Well,big ones to check..Tire pressure,plugs,O2 sensor(sub 1),let vehical warm up before driving...And ofcourse lead foot...also winter fuel will get 10% less than normal as well.

One other thing,Its a big misconception the air filter will cause drop in gas milage,this is not true for EFI..This only applies to carb intakes...EFI,through the MAP/MASS sensor will determine air flow if lower than normal the ECM will compensate and cut the "on time" of the injectors,keeping correct fuel trim by O2/A/F feedback..

Little first hand story:
I once saw an air filter box completely packed with dog food and cotton material...I mean so packed,had to use pliers,scraper to get it all out...Seems a squirrel found a nice cozey home...The car was in for a routine oil change and I check the air filter during the service.....The customer,had no clue,said it drove normal,No differant since they bought it new...And was still getting great gas milage!!..........I was suprised the engine was getting enough air to even run...Go figure:)

About the bad cat:First thing is your drivability will suffer if its partially clogged,Really bad ones can make vehical not be able to get over 35MPH...may also see a cat code pop up...There are a couple of checks for a clogged cat,You can hook up a vacuum gauge and at steady throttle once the vacuum gauge stabalizes if the cat is partially clogged the vacuum gauge will start to fall.You also can do a pressure readings tap at sub1 and sub 2 and compare readings..but no one or shop is going to go through that trouble.You can do a search through the internets if you want to learn more.....I highly doubt a bad cat is your problem w/o codes and/or any drivability problems...

One other thing to check,rear brakes..Makesure nothings is binding,bellcranks...axle seals swealling shoes

yes just for the seafoam treatment. there has been reports of seafoam ruining o2 sensors. i remove mine just in case

Come on now, winter in Texas? :hillbill:

If the OP is from Michigan, 12.5-13mpg is within "normal" for that cold of a climate, especially if you get more than 2 cold starts a day.