MPG Dropping Quickly!

trevo_man

trevo_man

New member
I purchased my 2000 SR5 (3.4 L) back in July. I have consistently fueled at the same Chevron, at the same pump, and pumped only until the first click on the pump handle. I drive the same commute (city only) every day with very minimal trips between.

In July I was measuring 19 MPG. Towards the end of August I was lucky to get 16 MPG. As of this week (late October) I am officially at 13 MPG.

Can anyone help explain why I might be experiencing such a sharp decline in fuel economy?

I tried switching to a full synthetic oil, with no luck. I have also tried driving with the ECT on for a couple fill ups, and a couple with the ECT off. It doesn't seem to make any difference. I am very conscious of the way I am driving, and make sure I have slow consistent acceleration (in other words, I drive like a Grandma).
 
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air filter, tire pressure, MAF cleaning, Plugs? Check all those first then come back..

Possible winter gas?
 
I replaced the air filter in July, and check tire pressure weekly. I was planning on plugs next, but hadn't thought of MAF cleaning. Thanks!

I wasn't sure if winter gas could have such an impact on economy, as I've never experienced such a drop with any other vehicle.

I did replace the timing belt & water pump back in July as well.

Anybody have any other thoughts on the sudden drop?
 
Colder temperatures can really affect MPG.

All of the fluids in the drivetrain are thicker when cold, and until they get up to operating temp. Which creates more drag, and hurts MPG.

When the engine is cold, the A/F mixture is richer until the engine reaches operating temp. Further hurting MPG.

If you let your engine idle on cold mornings so the truck is warm when you get in to drive, that can really have a negative effect on MPG. When an engine is running, but the vehicle isn't moving, it's getting 0 MPG.

The aforementioned winter gas blends also hurt MPG.

Look at it this way, you were getting great MPG for all City driving, when temperatures were hot.
 
OP, certainly not writing this to be condescending but would you mind posting your method for calculating your MPG 's? Reason I ask is that there are a lot of threads on this topic and I've seen quite a few crazy methods that lead to inaccurate results.
 
Mpg

I'm only averaging 12-13 mpg around town, 2001 Limited 4x4 with 95000 miles, it has new plugs, new air filter, MAF and throttle body cleaned before MPG was measured. I only drive it an average of 300 miles a month, but it's usually short trips around town. Even so I thought mine should be slightly better also. I treat this thing like glass and drive very easy, no idling.
 
A 3rd gen 4Runner is not great on gas. My '97 V6 5-speed was rated by Toyota at 15 MPG city, and 19 MPG highway.

Those figures were determined on a 4Runner that is fully warmed up, and operating as efficiently as possible.

The inefficiency of a cold vehicle driving around on city streets, could easily account for a 2-3 MPG loss. Especially with the ethanol content in modern gas.
 
Try changing pumps? Or Gas Station?
Also Fuel filter? (really easy to change, if you have not already done it)
Gas pumps need constant adjustment to stay accurate and usually are pumping lean to the stations advantage. Try to find a Chevron OWNED station because most are just franchised out. Also I have never ever gotten anything near 19MPG's in my 4runner.
 
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02SE said:
The inefficiency of a cold vehicle driving around on city streets, could easily account for a 2-3 MPG loss. Especially with the ethanol content in modern gas.
Click to expand...

Chevron does not use ethanol to the best of my knowledge even here in crazy tarded California they are the only stations and still serve up the real stuff
 
Just to way over nerdify this for you.

If you have anything that can read OBDII scan data you can compare to my little guide below and if you are out of range I can make a recommendation by that. Anything else is really just a guess.

I understand this may go beyond most comfort zones but I tried to keep it as simple as possible with no intrusive testing.


1. Check scan data for Long Term Fuel Trim (LTFT) and Short Term Fuel Trim (STFT). Look for 0% plus or minus 10% to be normal. See if the fuel trims are far negative meaning the Engine Control Module (ECM) is trying to take fuel away.

2. If the fuel trims are far negative, check scan data for the Mass Air Flow Sensor grams/second and calculated load. With a warm engine at idle and the A/C off, the Mass Air Flow (MAF) Grams Per Second (GPS) should be 3.3 to 4.7 and the calculated engine load should read 15 to 21%.
 
02SE said:
A 3rd gen 4Runner is not great on gas. My '97 V6 5-speed was rated by Toyota at 15 MPG city, and 19 MPG highway.
Click to expand...

Hmm. My 2002 with 200k plus miles get 19mpg mixed. Maybe 20. I don't think I would decide on keeping it if i were getting 15mpg.

My tires are 265/70/16 ht tread.
 
bpowa said:
Hmm. My 2002 with 200k plus miles get 19mpg mixed. Maybe 20. I don't think I would decide on keeping it if i were getting 15mpg.

My tires are 265/70/16 ht tread.
Click to expand...

Regardless, that is what Toyota rated my '97 at. As is often stated "Your mileage may vary".
 
A quick google search and your right, I was mistaken. They are are the only stations that do not have a written notice on their pumps about ethanol content.
 
bpowa said:
Hmm. My 2002 with 200k plus miles get 19mpg mixed. Maybe 20. I don't think I would decide on keeping it if i were getting 15mpg.

My tires are 265/70/16 ht tread.
Click to expand...


I'm not saying your wrong here, but I have a 98 4runner in great shape & 2001 4runner in Excellent shape, neither touch that MPG. I would have to say those numbers are very very optimistic, which leads others to think their 4runner is doing poorly.. when its not.
 
jsmith811 said:
I'm not saying your wrong here, but I have a 98 4runner in great shape & 2001 4runner in Excellent shape, neither touch that MPG. I would have to say those numbers are very very optimistic, which leads others to think their 4runner is doing poorly.. when its not.
Click to expand...

Its not rocket science to calculate mpg. I was testing it because I was considering selling it or keeping it.

MPG was one of the to keep or sell for me.

I live next to the gas station a couple blocks away. The gas light is lit up. I pump gas immediately.. put 7 gallons. I drove 140. miles the gas light comes on again, I went back to the pump.. I did this 3 times.. as a second vehicle I drove this a short distance from to and from work and I fill up right away when the light comes up.

This week I pumped a full tank. 16.5 gallons. so far the gas needle is over half full. and I packed on close to 160 miles. Im sure I can get over 300 miles before the gas light comes back on.

300/16.5= 18.8.. Maybe ill get 330 till the light hits, if I get less, I can account for the load from a full tank of gas..

Im not trying to turn this into a feud about MPG... Im just suggesting OP check all the maintenance items. BTW my tire psi is at 37cold..
 
In an effort to try to bring my fuel economy back up, I have done the following over the past 30 days:

*Replaced Spark Plugs with new Toyota Plugs
*Replaced the Fuel Filter with a new Toyota Filter
*Cleaned the MAF Sensor
*Checked Tire Pressure Regularly

I have tried about four other gas stations (Conoco, Chevron, Shell, and a Grocery Store Station), and am still getting 12-13 MPG.

I am filling up with 85, but I live in Utah so I have heard that 85 at this elevation is really like 88. Not sure if there is any truth to that.

Someone asked about my method for calculating MPG. I am filling up to one click on the pump handle every time and resetting the Trip on my odometer. I simply divide the amount of miles driven by the amount of fuel put into my Runner.

Any other thoughts on this drastic decrease? Like I said, only a few months ago I was driving the exact same commute and pushing 20 MPG. As much as I want to believe it is just the cold weather and winter blend fuel, that just seems like too significant of a drop.
 
Something's off for sure, not by much but it is. Just for reference I get 15-17 mpg with 3-4 inches of lift, 285's and a supercharger. That's at 4500 ft elevation too.
 
I too puzzled over this issue for along time, when i first bought my runner i was getting around 20 also (3.4 V6 & Automatic trans), one winter it just fell off a cliff to average around 14MPG now (in town) if i'm lucky i get 16MPG on the freeway. I chased allot of things trying to figure it out and have had no success either....

Please let us know what you find out!
 
Sorry but, if not letting the engine idle until warm, how else to get it warm? Even in summer weather, I always give my engine 2-3 minutes of warm-up time to come to operating temp. Not sure if this is even the right thing to do, but it's a habit written in stone for me.

02SE said:
Colder temperatures can really affect MPG.

All of the fluids in the drivetrain are thicker when cold, and until they get up to operating temp. Which creates more drag, and hurts MPG.

When the engine is cold, the A/F mixture is richer until the engine reaches operating temp. Further hurting MPG.

If you let your engine idle on cold mornings so the truck is warm when you get in to drive, that can really have a negative effect on MPG. When an engine is running, but the vehicle isn't moving, it's getting 0 MPG.

The aforementioned winter gas blends also hurt MPG.

Look at it this way, you were getting great MPG for all City driving, when temperatures were hot.
Click to expand...
 
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