Serious MPG Issue

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Aug 29, 2014
Lewisburg PA
I know I know another thread.....

I have an 89 62 - 214k - and she goes through gas like Hollywood does cocaine on Oscar Night..

I just got 3 mpg - on 15 gallons of fuel - (don't fill up all the way because I need a new fuel pump bracket and when the tank is full it leaks through the top of the tank it does not leak when not full)

I have consistently been getting around 7 mpg with a mix of city and hwy miles - on the hwy I recently got 9 mpg on a flat hwy cruising at 55mph with the engine warmed up-

so there is an issue - I have noy checked codes yet - planning on doing that this weekend - its supposed to be warm here on Sunday (35 degrees)

What I do know is this.. the 02 sensors are welded in so that is not such an easy replacement nor a cheap one - I have 31 inch tires and are properly inflated - I do not have a very long drive at all - less than a mile ( when it gets warmer I will walk ) I try to warm the rig up before I drive her off but not all the time- When she is warmed up she idles in drive around 700rpm/ in park or neutral around 1000rpm - I know that is a little high on both ends- She does run rich - I was thinking new O2 sensors would help but again they are welded in - The temp gauge barely moves above the first line and the front heat is moderately warm - Not sure when the last tune up was done -

Since it is very cold here I was thinking I would have a mechanic guy around town check it out -

So my question is what should I tell him to look at/ do - I do not have dreams of great mpg but dreaming of 12 hwy / 10 city would be awesome

Thanks so much ...
Are you leaking fuel somewhere besides the known issue? Without filling up all the way, how are you accurately getting this 3MPG figure?

Get the fuel tank problem fixed before you go chasing this MPG problem.

City MPG on a 214k mile motor isn't going to be the best, but no way it should be 3mpg

I used to live really close to work. 10 minute drive, all city. My FJ60 got 10-11 mpg. Once I had a longer drive (mostly highway) I would see 12-13mpg. Made me feel better even though the distance offset the fuel savings. lol
Agreed with Klinetime - must fix the fuel tank issue first...I get 12 city, 14-15ish highway.

If you drive it for 15-20 min, does it get hot? Does the exhaust smell rich and nasty? Do you have a check engine light or a code for oxygen sensors?

If the truck never warms up (even with a longer drive), I would check the cooling system and replace the thermostat, being careful not to snap off the t-stat housing bolts (spray them several days in advance, from above and below).

I would then buy and weld into the exhaust system 2 proper oxygen sensor bungs (they aren't super expensive), and remove (or leave) the old sensors. Then buy new sensors (Denso brand only) from Rockauto, or your dealer and install them. You might also check plug wires, plugs, etc.
I am not leaking any fuel what so ever -
I put 15 gallons in when I fill up and refill when the gas gauge on fully on E when the rig is on a level and warmed up - the new bracket is 250 bucks waiting on tax return to get it -
I replaced the theromstat a few months ago - when i was dealing with heater issues - before the replaced thermostat I got no heat - now i get moderate heat - Ill see about getting new O2 sensors and leaving the old ones -

Yes it runs rich - it doesnt smell too nasty to me - but definatly not normal

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