Greetings,
I have a 2001 Tribute that I'm still madly in love with - BAKFIXR, as I call him (my license plate.)

Well, in November I put on new tires (after sorely needing them for probably a few years) and my normal 18 mpg that I was getting suddenly dropped to 15?!? Since I reset the odometer with each fill and keep track (kind of **** about it) I was very surprised - someone told me bald tires get the best MPG, and that combined with the heavy use of 4wheel due to our nasty Minnesota winter so far, that maybe they would be the cause.

3 weeks ago I got an oil change and had them check my tire pressure - the tires were recorded at 26, 30, 32 and 35. All were set to 35 after that. We went on vacation shortly after, and so yesterday was my first fill up - I was so excited until I did the math - thinking SURELY it was going to be better, I recorded a whopping TWELVE (12) MPG?!?!?!?

Does ANYONE have any possible idea why the sudden drop? No check engine light is on, so I can't get it scanned for codes. Replaced the EGR valve in September. 141,000K miles on the BAKFIXR.

TIA,
drgray

 

Hello, a number of things can cause that and I know this might sound too simple, but you could change the fuel filter and air filter. Either or especially both being clogged can cause this. Let us know if you find the trouble.
Hope this helped.

 

Look for mice nests in the intake
Use of 4WD & letting the car warm up when you're scraping off the ice can make a big effect on the MPG, same with driving through more snow which causes more drag.
Look at those simple things, next on the list may be something like the O2 sensor, which can cause a large & sudden drop in mileage.

Also see if your temp gage is reading normally, if the thermostat got stuck open, and your engine is running cold, that would do it too.

 

thanks muchly - I think it could be a thermostat issue, which would be a simple fix. My thermostat zooms up to 1/2way between C and H in about 30 houses after leaving my driveway and enter my neighborhood. This could be a very simple easy fix.!

 

if it only takes 30 houses to get to mid temp, definitely sounds like a sensor problem. that's too fast for the engine to heat up even if it was stuck closed... that is unless 30 houses takes 2 miles distance.

 

Are the new tires the same size as the old ones? If the tire size is different the odometer reading will be wrong and so will be your math to calculate mpg.

 

service the car including plugs and filter. If that doesnt work it could be the o2 sensor(s) as these are generally recommended to be changed at around 100K

 

Yes tires are exactly the same size.

As for tune up, my very trusty mechanic said to wait until spring because we have had more 4WD usage in MN this year than I can remember ever living here in 22 yrs, and it's been dang cold - he has been getting a lot of calls on this and he thinks its a combination of letting your car warm up and the 4WD kicking in. He suggested I go 2 tankfuls after all the snow is gone and I don't have to let my vehicle warm up and then get new wires/plugs/fuel filter if it does not improve. Wouldn't my "check engine" light come on if it was an O2 sensor? I should note that we replaced the EGR valve last September when my light did come on - unrelated at this point I'm sure, but at least the idiot light works, right?

Picked up a $6 thermostat, as I think it would be a great cheap place to start - unfortunately, with 12 inches of snow yesterday, hubby didn't get it installed! Thanks for all the suggestions - I sure hope to get to the bottom of this and report back that the problem is SOLVED!
drgray

 

the o2 sensor can get pretty bad bad before the light comes on - causing poor mileage. it depends on the vehicle for how bad it gets before the computer says its completely failed via check engine light.

 

Okay, Dave - so do I just call my trusty mechanic and tell him to test it to see if he can trip it up or just go ahead and put a new one in?

Isn't that about a $250 part/repair? Is it better to "guess" at that or new wires/spark plugs/fuel filter (which reminds me that I better check on the last time those were done - so much for "lifetime" wires, right?)

TIA
drgray