TERRIBLE mpg!

S

seanshreds

Member
Hey guys, I keep seeing these threads about how people are getting 16-17 city with their built runners and getting over 20 highway and I was wondering if anyone could help me out. I am stock and drive in my opinion quite conservatively and I get pretty bad mileage. I used to get about 16 or 17 city and around 20 highway but lately, more like a while now, I have been getting about 13 city and I do not drive highway very often so I do not even know what that is. If anyone has any advice on how I can get my mpgs back it would be VERY appreciated!
 
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Tune up comes to mind if it's been a while, plugs and wires. Also, a stuck thermostat (stuck open) is a often-forgotten cause of terrible mileage. Another culprit that's cheap and easy is the PCV valve, and don't forget that fuel filter. Might be a good idea to try some fuel system cleaner, I used Lurbo Moly gasoline treatment every so often.

If you haven't been driving highway in a while it may be a good idea to run her out on the interstate and get it good and hot, especially after giving it a tune up and fluid change. City driving typically doesn't allow the engine to burn off condensation which causes carbon deposits.
 
JEL said:
Tune up comes to mind if it's been a while, plugs and wires. Also, a stuck thermostat (stuck open) is a often-forgotten cause of terrible mileage. Another culprit that's cheap and easy is the PCV valve, and don't forget that fuel filter. Might be a good idea to try some fuel system cleaner, I used Lurbo Moly gasoline treatment every so often.

If you haven't been driving highway in a while it may be a good idea to run her out on the interstate and get it good and hot, especially after giving it a tune up and fluid change. City driving typically doesn't allow the engine to burn off condensation which causes carbon deposits.
Click to expand...

Is the thermostat something that I would have to have my mechanic do? I didn't even know our trucks had them! and is the PCV valve the one that you pull the hose off of for the sea foam treatment? the little white right angle hose fitting thing?
 
Definitely not a tough job, the thermostat that is. Is the engine running cool? I don't know how bad or good these gauges are on these rigs to be honest, but I used used a scanner on my Ford and, even though the gauge (more like an idiot "needle") read normal, it was running around 150*f, sure enough the t-stat was stuck open, my mileage returned to normal in that truck.

I've never done Seafoam, but the PCV is that little white valve on the passenger side with the hose going to it, just install a new OEM one if it's been a while.
 
i always get a kick out of people w 4runners saying they have bad mileage. you didnt see that on the window sticker? i did o2 and i swear it got worse. half this crap is a mental game.
 
How's this for gas mileage?

31's= 300-320miles/tank
33's= 260-280miles/tank

Now on 35's I get 200-220miles/tank and that's mostly hwy driving:crazy::cry2:
 
KSWAY said:
How's this for gas mileage?

31's= 300-320miles/tank
33's= 260-280miles/tank

Now on 35's I get 200-220miles/tank and that's mostly hwy driving:crazy::cry2:
Click to expand...

i get 250-260 w 35s and 4.10s

do yourself a favor and get a scanguage II. they are extremely accurate. and i know i get better gas mileage now, because you have real-time MPG monitoring, engine temp, TPS, avg mpg, etc. it also has the ability to change your speedo (just on the gauge), and the trip function shows DTE, Time to empty, total miles, etc. its freakin awesome.
 
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I wouldnt blame the o2 sensors, thermostat, pvc valve, or even bad oil, etc just yet. Over the past few months my mpg has been down from 20ish highway to 15.5ish highway. Thats a big difference. I think the culprit is just the winter gas and temps. I dont know exactly why winter gas produces worse mpg (perhaps someone with this knowledge could inform us), but I do know its pretty common. I fully expect my mpg to go back up as it gets warmer without doing any maintenance.
 
Hi Sean,

We haven't met in person but I think I know your Dad. Unless there is another another Sean in Encinitas with a Shred-Runner.

About the gas MPG: if you really are getting < 15 on average in the city then there is a chance something is up.

How do you calculate MPG? I prefer to use a free app "fuel log". The method is fill up your gas, zero out your trip meter, start the app and put in first fill up. At next fill up be sure to fill tank all way full again and put details in the app. Sorry but a lot of guys actual miscalculate.

Assuming the worst and it is 13-ish MPG. You may need to do some preventive maintenance.

After 10 years the following should be replaced:
* spark plug wires
* spark plugs
* Fuel filter

Also make sure your air filter is clean. There is more you can do if that doesn't solve it.

Be sure to only use OEM (Real Toyota) parts either from a vendor or dealership.
You can buy real Toyota parts at about 25% off online from several places.
With the 4Runner only Toyota OEM spark plugs should be used, putting "performance Bosche" in will actually make it run worse. Basically don't buy any engine parts from AutoZone.

Lastly, don't SeaFoam your truck without careful consideration of all the facts. Some guys here believe in the SeaFoam treatment but it isn't a guaranteed fix and may actually cause more problems.
 
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1985taylor1925 said:
I wouldnt blame the o2 sensors, thermostat, pvc valve, or even bad oil, etc just yet. Over the past few months my mpg has been down from 20ish highway to 15.5ish highway. Thats a big difference. I think the culprit is just the winter gas and temps. I dont know exactly why winter gas produces worse mpg (perhaps someone with this knowledge could inform us), but I do know its pretty common. I fully expect my mpg to go back up as it gets warmer without doing any maintenance.
Click to expand...

It's hard to say what difference it would make around San Diego, but I know temperatures aren't going to be the culprit. Winter fuel perhaps, but I don't know if they get the same stuff as you guys in the upper Midwest? I think it's reasonable to assume the truck hasn't been tuned up, I was getting a minor misfire from bad wires, so I went through and did a complete tuneup (replaced the t-stat when I did the new radiator to avoid the milkshake) and, sure enough I got 19.7mpg on my last trip up over the mountain passes here in Wa. Before I was around 15mpg highway. The passes here are very steep and I spent a lot of time over on the dry side with temps falling to about 10f at night, closer to zero at altitude.
 
Winter blend and warm up times killed my mileage, went from 20 to 15. I just did a tune up (MAF, throttle body, oil change) halfway through my last tank and I managed 17. I'll see what I get with my next full tank before deciding what to do next.
I'd recommend doing something similar to see where you can get improvements before doing anything drastic.
 
Same here man, i get like around 10mpg and overall 190 miles to the tank. and how much can a 98 4runner tank hold?
 
brianemc2_42 said:
Hi Sean,

We haven't met in person but I think I know your Dad. Unless there is another another Sean in Encinitas with a Shred-Runner.

About the gas MPG: if you really are getting < 15 on average in the city then there is a chance something is up.

How do you calculate MPG? I prefer to use a free app "fuel log". The method is fill up your gas, zero out your trip meter, start the app and put in first fill up. At next fill up be sure to fill tank all way full again and put details in the app. Sorry but a lot of guys actual miscalculate.

Assuming the worst and it is 13-ish MPG. You may need to do some preventive maintenance.

After 10 years the following should be replaced:
* spark plug wires
* spark plugs
* Fuel filter

Also make sure your air filter is clean. There is more you can do if that doesn't solve it.

Be sure to only use OEM (Real Toyota) parts either from a vendor or dealership.
You can buy real Toyota parts at about 25% off online from several places.
With the 4Runner only Toyota OEM spark plugs should be used, putting "performance Bosche" in will actually make it run worse. Basically don't buy any engine parts from AutoZone.

Lastly, don't SeaFoam your truck without careful consideration of all the facts. Some guys here believe in the SeaFoam treatment but it isn't a guaranteed fix and may actually cause more problems.
Click to expand...


Brian, you do work with my dad haha and I calculate my mileage by reseting the trip meter every time I fill up then when i need to refill again I divide the miles by how many gallons, pretty simple. As for everyone else, the people saying that it is winter gas, I feel like it went down a little while before that but it is weird because of how quickly it changed. It used to be pretty decent but within a week maybe two it went down to like 13. I have cleaned my air filter and have a new one that I will probably put in soon. I also do not know when the last time the sparkplugs/wires/fuel filter or any of that was replaced. Maybe I will put that up next on my list of things to do! Also, would a crappy after market catalytic converter have an effect? The guy before me put one on but my mechanic said I should notice anything.
 
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