From decent to bad: Gas mileage

[Mudeprived]

Truck has been thirsty lately and I am not sure if my mileage is normal, decent, or bad so I am asking what you guys are getting so I can compare. Lately the fuel light has been coming on at 200 miles which is a bit odd. I don't trust it so I get gas anyways. I would fill it up and have 3 gallons left. From what I have read, about 2 gallons in the tank is "unreachable" so I calculate based on a 16.5 gallon tank and coming up with 250 miles per tank, or roughly 15 mpg. I bought this truck last December and have gone 300-310 miles sometimes. I ran out of gas twice just before 310 miles.

So it seems like I have lost a bit of mileage. I have not made any changes to anything that would affect it, however, I have had a leaking driver's side rear axle seal that I fixed but it has already saturated the shoes and they stick alot when i come to a stop. Drag maybe? It does not pull and momemtum keeps it moving at idle. I also had a strange type of shaking/misfire at idle a couple weeks ago and took it to the shop. They sprayed MAF cleaner into the TB and that cleared it up. I am not sure if that is related to anything but it is running pretty normal. I say pretty normal because the idle isn't completely still like it used to be. You can feel it idling unlike before it was almost silent. This truck had the smoothest idle of any vehicle I have driven in and it was pretty impressive.

Am i just being anal about gas mileage or could something really be going on?

 

[pluton]

The only mileage test that works for me is during long trips on open highway, since my work locations/everyday driving vary.
I measured 19 MPG @75MPH, A/C on, summer hot outside. 5-speed trans, driving in 5th gear, no big hills or wind.
They say cold winter conditions means worse mileage no matter what else is going on with the vehicle.
Don't these trucks have 18.5 gallon tanks?
Also, you have taller/heavier tires so it's not likely you'll match another 4Runner that has stock 265/70s.

 

[Mudeprived]

The only mileage test that works for me is during long trips on open highway, since my work locations/everyday driving vary.
I measured 19 MPG @75MPH, A/C on, summer hot outside. 5-speed trans, driving in 5th gear, no big hills or wind.
They say cold winter conditions means worse mileage no matter what else is going on with the vehicle.
Don't these trucks have 18.5 gallon tanks?
Also, you have taller/heavier tires so it's not likely you'll match another 4Runner that has stock 265/70s.

Same tire size since day one and same daily commute at night with very little traffic or stopping at speeds 50 or under. Yes it has a 18.5 gallon tank but I can only put in abt 16.5 dry. Research here tells me that there is 2 gallons of gas in the tank that the pump cannot reach.

I understand abt cold weather affecting mileage but a 50 gallon difference?

 

[19963.4lsr5]

When I fill up at the 1/4 tank mark it's always 12gal. You should do the milage check. Taking the tank low all the time to me allows for more chances to have fuel pump failures. The gas it sits in and pumps is what cools it too.

You should also have a scanner that reads live data and look at the LTFT and make sure your going into closed loop.


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[Ed_C]

Could be brake drag,mileage dropped drastically on my 4th gen and discovered both front calipers were seized.

When was the last time you did a “tune up”? As in replace the air filter,plugs,wires,PCV valve.

My daily drive (commute) is mostly highway (might as well be stop and go in the morning though), I usually fill up around 310-320 miles. ‘02 V6 auto,stock suspension,all-season General tires in the narrower OEM size (245/75-16)

 

[Mudeprived]

Could be brake drag,mileage dropped drastically on my 4th gen and discovered both front calipers were seized.

When was the last time you did a “tune up”? As in replace the air filter,plugs,wires,PCV valve.

My daily drive (commute) is mostly highway (might as well be stop and go in the morning though), I usually fill up around 310-320 miles. ‘02 V6 auto,stock suspension,all-season General tires in the narrower OEM size (245/75-16)

Did a full tune up in March. No brake drag up front cuz I just had it off the ground for drivers cv bearing fix and wheels spun freely. I have to check the rear.

It only ran out of gas twice cuz fuel gauge was not going past 1/4 when i bought it and I did not know this so I ran out around 310. Suddenly it started working a few months ago and it seems somewhat accurate according to my mileage and fill ups. Light pops on with abt 3 to 4 gallons left.

Would it not going into closed loop cause a CEL?

 

[19963.4lsr5]

The ruff idle etc has me wonder about how old the front O2 sensor is. The don't always set a code when they go bad.


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[Mudeprived]

The ruff idle etc has me wonder about how old the front O2 sensor is. The don't always set a code when they go bad.


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Brand new and so is the rear. I just replaced em over the summer. It is a California Emission rig.

 

[19963.4lsr5]

Brand new and so is the rear. I just replaced em over the summer. It is a California Emission rig.

You put gaskets on them and used Denso or NTK?


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[thezentree]

As a reference point, I was averaging (50/50 hwy/city) a really consistent 18.5-19mpg on 265/70R16s before I lifted mine.

 

[Mudeprived]

You put gaskets on them and used Denso or NTK?


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Yes on gaskets and it was Denso.

As a reference point, I was averaging (50/50 hwy/city) a really consistent 18.5-19mpg on 265/70R16s before I lifted mine.

That's about what I was getting. Mine is not lifted, just 265/75 All Terrains.

 

[phattyduck]

From what I have read, about 2 gallons in the tank is "unreachable" so I calculate based on a 16.5 gallon tank and coming up with 250 miles per tank, or roughly 15 mpg.

You don't calculate based of the tank size. You need to take the actual amount of miles you drove since the last fill up and divide the the actual amount of gas you filled up with. That's Miles per (divided by) gallon = mpg

More likely you are filling up with around 14 gallons in 250 miles and you are getting ~18mpg. That's quite normal, depending on driving style and terrain. (I get ~16 in my normal commute driving and ~22 on road trips)

-Charlie

 

[gamefreakgc]

Truck has been thirsty lately and I am not sure if my mileage is normal, decent, or bad so I am asking what you guys are getting so I can compare. Lately the fuel light has been coming on at 200 miles which is a bit odd. I don't trust it so I get gas anyways. I would fill it up and have 3 gallons left. From what I have read, about 2 gallons in the tank is "unreachable" so I calculate based on a 16.5 gallon tank and coming up with 250 miles per tank, or roughly 15 mpg. I bought this truck last December and have gone 300-310 miles sometimes. I ran out of gas twice just before 310 miles.

So it seems like I have lost a bit of mileage. I have not made any changes to anything that would affect it, however, I have had a leaking driver's side rear axle seal that I fixed but it has already saturated the shoes and they stick alot when i come to a stop. Drag maybe? It does not pull and momemtum keeps it moving at idle. I also had a strange type of shaking/misfire at idle a couple weeks ago and took it to the shop. They sprayed MAF cleaner into the TB and that cleared it up. I am not sure if that is related to anything but it is running pretty normal. I say pretty normal because the idle isn't completely still like it used to be. You can feel it idling unlike before it was almost silent. This truck had the smoothest idle of any vehicle I have driven in and it was pretty impressive.

Am i just being anal about gas mileage or could something really be going on?

Not that I advocate running on every last drop of fuel, but the way the tank is designed there's an indent at the bottom right where the fuel pump is. I had to drop my tank to replace the fuel pump recently and noticed how low the fuel really was. It can suck up pretty much every last gallon.

I've filled 18+ gallons before. I ran out of gas once and literally rolled into the station in neutral.

 

[Mudeprived]

You don't calculate based of the tank size. You need to take the actual amount of miles you drove since the last fill up and divide the the actual amount of gas you filled up with. That's Miles per (divided by) gallon = mpg

More likely you are filling up with around 14 gallons in 250 miles and you are getting ~18mpg. That's quite normal, depending on driving style and terrain. (I get ~16 in my normal commute driving and ~22 on road trips)

-Charlie

I did. I got fuel at 200 miles recently when the light came on and filled 13.5 gallons which is a little under 15 mpg. I haven't tried going 250 miles in fear of running out again based on the calculations but in the past I could go 300 before needing gas.

 

[Mudeprived]

Not that I advocate running on every last drop of fuel, but the way the tank is designed there's an indent at the bottom right where the fuel pump is. I had to drop my tank to replace the fuel pump recently and noticed how low the fuel really was. It can suck up pretty much every last gallon.

I've filled 18+ gallons before. I ran out of gas once and literally rolled into the station in neutral.

Well like I said I ran out of gas twice. The first time I put almost 5 gallons in via gas can and do not remember how much I put in at the gas station cuz it was a bit of a drive and did not think to calculate. The second time I put 2 gallons in and drove to gas station (apaprox 100 yards away) and only could get 14.6 gallons in. That's 16.5 approx.

Today I ran some errands and have 92 miles on the tank so far. Needle is at half mark. This is what I have been seeing and I keep thinking the gauge is fubar but the amount of gas I put in when I do fill up says that it is somewhat accurate.

 

[19963.4lsr5]

In western PA how long do you let the engine run before you start driving this time of year?

Letting it idle 10 min to warm up and then driving 5 miles will really wreck your gas milage.

I start driving around the time the fan slows down after a cold start.


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[Mudeprived]

In western PA how long do you let the engine run before you start driving this time of year?

Letting it idle 10 min to warm up and then driving 5 miles will really wreck your gas milage.

I start driving around the time the fan slows down after a cold start.


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Just about a minute, not much different from my usual. I haven't had any real cold days yet where I have to scrape ice off so it's basically been get in and go. It is running at a higher rpm for the first mile or two, which I assume is the way the truck warms up faster, so I thought maybe that was contributing to it in a way.


I have driven Jeeps for years before this and I always calculated mileage throughout the year just to keep a tab on how it is running and if anything is affected fuel mileage and I been doing the same with this truck since I ran out of gas back in Jan. I never had this big of a change in gas mileage in any vehicles so I am assuming something is going on. I bought this truck pretty much a year ago so I am still "learning" it's habits but this still seems unusual.

 

[phattyduck]

The second time I put 2 gallons in and drove to gas station (apaprox 100 yards away) and only could get 14.6 gallons in. That's 16.5 approx.

I have seen a theory on here that the 'short' fill ups are more due to the vent tube going down into the tank farther on some trucks (I think 1999 is the year). If the pump is stopping due to the vent tube getting covered (how the auto-shutoff works), then really what is happening is that you are missing 2 gallons at the 'top' of the tank, not the bottom. Not sure if there is any truth to that though. I do know that if I ever drop the tank, I'll be cutting some off that tube to see what it does to my capacity.

15mpg in winter with mixed driving isn't too horrible...

-Charlie

 

[nissanh]

Hold on guys.... While I was working the valve cover gaskets I found something that "might" influence the gas mileage. Still in the testing period, so in few days I'll let all of you know.

 

[gamefreakgc]

Well like I said I ran out of gas twice. The first time I put almost 5 gallons in via gas can and do not remember how much I put in at the gas station cuz it was a bit of a drive and did not think to calculate. The second time I put 2 gallons in and drove to gas station (apaprox 100 yards away) and only could get 14.6 gallons in. That's 16.5 approx.

Today I ran some errands and have 92 miles on the tank so far. Needle is at half mark. This is what I have been seeing and I keep thinking the gauge is fubar but the amount of gas I put in when I do fill up says that it is somewhat accurate.

It's probably your filler neck or something shutting the gas nozzle off early. I bet you could still pump 2 more gallons in there, you should be able to get the full 18.5 in there.