Fuel economy keeps INCREASING. Need help or ?

HighMiles

HighMiles

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I have had my 96 Ltd for almost 200 000 kms.

This last year it has been getting better and better fuel economy as I travel the same route regularly.

I would normally get about 500 km per tank, and it has been slowly increasing to having the low fuel light come on at 730 kms. I now normally get between 29 and 33 mpg highway, used to get 20 to 23 mpg. It has almost 470 000 kms on it.

Though this seems like a good thing, and I am saving a lot on fuel, but the fact it is changing makes me a bit concerned.

It is not starving for fuel; put the foot to the floor and it takes off. Still hits 160 km/h (100 mph) in a reasonable amount of time for a Toyota, though that sucks the fuel back.

Could something be leaning it out? I have not pulled the plugs in the last several years to check, and I am not sure how dark they should be either. Never changed the fuel filter. Hopefully the previous owner did. lol.

I am pretty sure that the engine would have broken in much earlier than 430 000 kms, or there would be build threads boasting the high mile engine swap fuel economy upgrade. ;-)

Any thoughts would be welcome. I guess there are worse problems to have, but I travel a lot and need continued reliability.

Thanks for any feedback.
 
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HighMiles said:
I have had my 96 Ltd for almost 200 000 kms.

This last year it has been getting better and better fuel economy as I travel the same route regularly.

I would normally get about 500 km per tank, and it has been slowly increasing to having the low fuel light come on at 730 kms. I now normally get between 29 and 33 mpg highway, used to get 20 to 23 mpg. It has almost 470 000 kms on it.

Though this seems like a good thing, and I am saving a lot on fuel, but the fact it is changing makes me a bit concerned.

It is not starving for fuel; put the foot to the floor and it takes off. Still hits 160 km/h (100 mph) in a reasonable amount of time for a Toyota, though that sucks the fuel back.

Could something be leaning it out? I have not pulled the plugs in the last several years to check, and I am not sure how dark they should be either. Never changed the fuel filter. Hopefully the previous owner did. lol.

I am pretty sure that the engine would have broken in much earlier than 430 000 kms, or there would be build threads boasting the high mile engine swap fuel economy upgrade. ;-)

Any thoughts would be welcome. I guess there are worse problems to have, but I travel a lot and need continued reliability.

Thanks for any feedback.
Click to expand...

You have a 4banger or V6? If you have 3.4 then you shouldn't be seeing much over about 320 miles give or take 20 (or 514~ kilometers in your case). No way you can be getting 450 miles ( 730 kilometers ) per tank with the 3.4l unless your driving downhill with a tail-wind and your three fattest friends riding in the back to help overcome wind resistance.

Something else is out of whack. The fuel pump, your speedometer, your math....something. How are you calculating your mileage? Or do you guys call it kilometerage?

If it's a 4 cylinder then I have no idea what they get.
 
It is a 3.4 Limited.

I drive from Calgary to Penticton every month, through the Rockies. I have put almost 200 000 kms on it, so I have a good feel for what is normal for it, and 500 km highway was it. Sometimes 525.

There is no room for a math error as I fill up before I leave. The distance is 686 km according to Google, and I used to have to fill along the way, now I drive straight through with a bit fuel to spare. Both ways, which eliminates the elevation change. Never arrive on a low fuel light.

2 months ago this was my best tank as I drove it in town down to the low fuel light after arriving home:

highmiles-albums-1996+4runner-picture41971-low-fuel-light-just-came-one-tank-fuel-trip-through-rocky-mountains.jpg


I have a friend with a 99 SR5, and have been sending him photos like these as his highway travels have been 400 km on 55 litres of the 65ish litre (?) tank.

I had found a cracked vacuum hose a while back (it runs absolutely smooth) and thought that may be it, so I reluctantly replaced it. Did not change anything.

Down stream 02 sensor failed, left it alone, did not change it either. Upstream 02 sensor now has a leak around it, did not change anything.

The Toyota dealer has nothing to say other than that it is very interesting, my daughters say their angels are pushing us along the way or adding gas to the tank. They maybe on the right track as it always goes farther with them in the car, no matter which direction we travel.

It has me really scratching my head, but it is consistent.
 
And by the way, thank you for replying and taking this seriously.

This sounds ridiculous, it seems impossible, but it is happening.
 
One more thing.

I have not replaced the injectors or fuel pump, and there was nothing in the maintenance folder from the previous owner, 200 k ago, indicating they were replaced.

I would expect, if anything, that the injectors may not be atomising the fuel as well as new which should be causing this old guy to be using more fuel than normal.

I replaced the plugs a couple years ago, but everything else is original.

It has close to 290 000 miles (467 000 km) on it.
 
KidVermicious said:
I'd make sure you're really seeing what you're seeing. Use your phone's GPS to make sure the speedo and odo are accurate.
Click to expand...

Double check this too. Never heard of a speedometer or odometer go bad but I guess it could happen.

Only other scenario is that your engine is running stupid lean, but for some reason not throwing the lean code. If you want your 4Runner to last better get someone to look at it or it will consume itself (read overheat/melt).
 
Haha!! I am loving this thread! Subscribing to see the outcome of the holy 4Runner!!
I can't see how the heck you can be getting such good mileage! Maybe we all need to rip out our 02 sensors XD
 
Even if the odo/speedo were reading wrong, he's basing this off of the trip he usually takes as well. If he has significantly more in the tank or can start the return trip without refueling, that is unrelated to a false readout. Intriguing.
 
You'll have to provide numbers.
How many kilometers driven and how many liters to fill.
And getting the distance from a gps and not the odometer.

For our American friends, our gallons are bigger.
 
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30mpg, even using imperial gallons, is insane (20 miles per US gallon = 24 miles per Imperial gallon). Maybe you're running super lean and you have a failing fuel pump?
 
The most I ever got on my 4banger was 23mpg when the truck was new. On 265/70R16 HTR's, all highway 55-60mph on the way to my Sisters house.
Last week I got 17.3mpg & I usually get 16.5 with my 33" MT's. I was happy with the slight increase.
 
The only thing I can think of is a 'faulty' (read 'fixed') fuel gauge.
Unless I missed it in a post somewhere, you are basing this off of the fuel gauge and no hand calculations. Even when you say you can make the trip from Calgary to Penticton without filling up, that's still only based on the gauge.

The 3rd gen fuel gauges are notorious for 'failing' and the fuel light showing up at around 5 gallons (18.9 liters) left (so they take about 13 gallons (46 liters) to fill). If you are basing it off of this, then if the gauge 'fixed itself' it looks like you can go an extra 4-5 gallons worth, which makes it seem like you have better mileage.
(question, is it the fuel gauge or fuel pump that causes this 'inaccuracy'? Doesn't really matter with this issue, but still)

The only way to know for sure: Do a hand calculation.
Make sure that your speedo and odo are correct via a phone app and then top your tank off. Set the trip counter to 0. Drive till the gauge reads half empty (or really any amount; half is just an easy number) then fill it back up. Divide the miles driven from the trip counter by the amount of gallons it took to fill.
Do this a few times and take the average. Doing it one time will get you a decent idea, but results may vary slightly.

Even with your saying that you can now get up to 730 kms (which translates to 454 miles for us Americans), it still seems to indicate faulty sensors (gauges, whatever).

If your numbers ARE accurate, then I don't see how you can be getting 100+ miles more without doing SERIOUS damage to your engine.
 
HighMiles said:
And by the way, thank you for replying and taking this seriously.

This sounds ridiculous, it seems impossible, but it is happening.
Click to expand...


My next question is how fast do you drive? If you have a 96LTD I'm going to assume you have the E-locker correct? If so I think your truck has 4.30 gears like mine does. Now I don't know how accurate my ScanGauge is for reporting MPGs while you are driving, but I've seen it read 25-30 mpg while I'm driving at slower speeds, so perhaps you are driving at a certain speed that is some kind of MPG sweet spot?

Failing that, my next best guess is that one of your friends, family or coworkers is just trolling you for shits & giggles. They are probably adding a few gallons to your tank when you are not around.

Tell all your friends, family and coworkers about how your MPG have strangely gone up and then take note of who can't look you in the eye without a shit-eating grin.
 
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StreetCreeper said:
Failing that, my next best guess is that one of your friends, family or coworkers is just trolling you for shits & giggles. They are probably adding a few gallons to your tank when you are not around.

Tell all your friends, family and coworkers about how your MPG have strangely gone up and then take note of who can't look you in the eye without a shit-eating grin.
Click to expand...

StreetCreeper for the win maybe!
 
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