I used to habitually get 15-18 MPG depending on where I was driving.
With fuel prices going up as much as they are, I have gotten into the habit of checking my MPG every time I fill up.
I have been doing this for the past couple of months.
The last few are disturbing me.
the first was in the mid-13 range.
then 12.8, then 12.2, and most recently 11.7
I have no idea what would cause this continual decline.
I know the truck is overdue for a tune-up and will be getting one as soon as I can get the parts together and find the time to get them in, but I am wondering what would cause this.
On my tune-up I intend to replace:
Plugs, wires, cap, rotor, PCV valve, breather filter, and air filter, and most likely her regular oil change will be done at the same time.

Any ideas?

 

That tune up sounds great. (Make sure you use single-electrode plugs only, the multiple electrodes aren't good)

Somethings to keep in mind: if you are driving with the A/C on or driving more city miles, that could explain the decline.

Along with the tune-up, if your going to change your engine oil, you may want to change your differential oil. (This should usually be replaced every 20-30,000 miles) 75W-90 or 75W-140 gear lube will work perfectly.

As a side note (it will not help your mileage), take the time and lube the lube points. I know the upper ball joints and tie-rods will take grease. I'm sure there are a few other places in the front and the rear that might take grease.

Also, make sure your tires are properly inflated, alignment is ok, and do a tire rotation. (The first two, of course, can effect mileage)

You may also want to run some fuel injector cleaner (I hear Chevron's Techrons' cleaner is good, but I can't speak for it... right now at least).

Hope this helps a little, and post back!

 

remember not only does the AC decrease mileage but so does the outside temps and when it's hot outside you engine is even hotter inside and that robs your car of HP and makes it work harder

 

The plugs I plan to use are the Champions.
Thanks for the info about all the lube points and the differential lube.
I plan to do a full fuel system treatment.
I just properly inflated my tires.
I knew the A/C would kill it, and I guessed about the heat.
The heat killed a lot of batteries, so I guessed that it was hard on the entire engine.
But it is good to know that it is a fact instead of just my guess.

The other day, I noticed a puddle under my truck after she had been sitting for a while. The liquid was about a yellow color, but the oil on my dipstick was darker.
As far as I could tell, it was coming from the lowest point of where my serp. belt is. I am hoping it is nothing too bad, but this truck hasn't leaked anything since I got it almost 2 years ago, so it worries me.

 

That might be a coolant leak; check your hoses and there is a weep/drain hole near the base of the impeller shaft on the water pump (if it leaking there you'll need a new pump).
Regards,
Greg

 

dumping some STP Fuel injector/ carburetor cleaner in the gas tank helps also

 

i have never got more then 14 wat is up with 17 lol

 

I get 17 with my cruise control on with the wind behind me.

 

i got 21 on my last tank
I gained 5-8 MPG after a tune up,
Plugs(bosch) Wires(bosch) cap and rotor.
ran a bottle of STP octane boost through.
runs a hell of a lot better.
$50 at AZ

________
Prilosec Class Action Lawsuit

 

Batman, I cay you have a *little* advantage with the 4 cylinder engine and stick.
Sadly noy my tune-up will have to wait until I can get the Water Pump fixed.
The Water Pump can leave me stranded while a tune-up just helps my truck run it's best.

So apparently, next on the list is:
Water Pump, Upper and Lower Hoses, Thermostat and gasket.
Any other suggestions while it is getting done?