Did Tune-Up. City mileage up, HWY down?!

[Cranmaro99]

When I bought my 2001 5.0 Limited AWD Explorer at 114k miles it got 11mpg city and 17 hwy.

I did a tune up on it (all fluids to synthetic, fuel filter, plugs, wires, pcv system, cooling system flush and new radiator and new thermostat. I did a lot of stuff as well as smaller things.

My city has gone up to 14 mpg, which is nice! But my hwy mileage is now 15 tops.

Ideas? I've tested over numerous tank fulls before and after with different driving conditions.

 

[koda2000]

When I bought my 2001 5.0 Limited AWD Explorer at 114k miles it got 11mpg city and 17 hwy.

I did a tune up on it (all fluids to synthetic, fuel filter, plugs, wires, pcv system, cooling system flush and new radiator and new thermostat. I did a lot of stuff as well as smaller things.

My city has gone up to 14 mpg, which is nice! But my hwy mileage is now 15 tops.

Ideas? I've tested over numerous tank fulls before and after with different driving conditions.

what brand and type of plugs did you put in it? what did you gap them at? for some reason these engines seem to work best on Motorcraft (or Autolite) platinums or double platinums gapped to .054. did you use a Motorcraft PCV valve? also, what tire pressure are you running?

 

[Cranmaro99]

what brand and type of plugs did you put in it? what did you gap them at? for some reason these engines seem to work best on Motorcraft (or Autolite) platinums or double platinums gapped to .054. did you use a Motorcraft PCV valve? also, what tire pressure are you running?

Autolite platinums, gapped to .055. Motorcraft PCV, as well.

Will get back to you on tire pressure but I usually check it once a week because I'm **** like that.

 

[Cranmaro99]

Tire pressure is good as always. Not sure what else to check as this is an unique situation, haha.

 

[Turdle]

Do you feel a slight stumble--vibration at about 2100-2200 rpms under slight load?

I suggest closing the plug gap down to about .052 --although I cannot see this making that much of a difference.

I suspect a bad plug or wire out of the box. Take them out and regap them a bit tighter, and, look closely for a misfiring plug by comparing the color-

I've seen this more than I would like , to be honest. Also, triple check the firing order, it is easy to cross a couple plug wires.

We've all pulled that one I think.

Edit: New air filter. Try one.

 

[Cranmaro99]

Do you feel a slight stumble--vibration at about 2100-2200 rpms under slight load?

I suggest closing the plug gap down to about .052 --although I cannot see this making that much of a difference.

I suspect a bad plug or wire out of the box. Take them out and regap them a bit tighter, and, look closely for a misfiring plug by comparing the color-

I've seen this more than I would like , to be honest. Also, triple check the firing order, it is easy to cross a couple plug wires.

We've all pulled that one I think.

Edit: New air filter. Try one.

Have a new air filter, too. I did it all, haha!

I will check the plugs. No stumble though, the car is running tip-top.

 

[koda2000]

maybe it has nothing to do with the engine. maybe a bad wheel bearing or dragging brake caliper or parking brake??? although i would think that would adversely effect city mileage too. next time you get off the highway, check the temp of your wheels with your hand to see if ones warmer that the others.

 

[Cranmaro99]

maybe it has nothing to do with the engine. maybe a bad wheel bearing or dragging brake caliper or parking brake??? although i would think that would adversely effect city mileage too. next time you get off the highway, check the temp of your wheels with your hand to see if ones warmer that the others.

Will do. I'm also thinking it isn't engine related (if it is anything.) The fact that city mileage went way up but city went way down (aka I pretty much get the same mileage however I drive) is really weird.

I'm thinking there's some friction going on somewhere, even though the car seems to be driving fine.