4Runner4Leon
Senior Member
Amalik, your coolant is at 211, mine's at 188. Could that be part of my issue?
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Consider me impressed.. 24 MPG!
- Thread starter TejasRunner01
- Start date
4Runner4Leon
Senior Member
Oh, I'm guessing you were stopped, so that's probably soakback temp.
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My thermostat is really old, from God knows when, it needs to probably be replaced and is likely not at the right jiggle valve position. And yes, I was stopped.
4Runner4Leon
Senior Member
I'm completely confused, or else my truck is bipolar. I just got 25.3 mpg over the last 40 miles of combined freeway and stop and go traffic, how is that possible???
To review my trip over the past few days (and why I think my truck is bipolar):
- First 100 miles = 15.3 mpg (mostly 70 mph), which obviously I wasn't happy with (this was measured by miles driven / gal to fill, realizing that there's always some error in when the pump stops).
- Next 225 miles = 17.5 mpg (about half freeway at 70 mph, half back roads with stop lights, about 60 mph)
- Next 160 miles = 17.5 mpg (all at 75 mph, cruise set).
This is when I read this thread and decided to use Torque Pro to pay closer attention (until then I thought this was normal for our trucks).
- Next 160 miles = 16 mpg according to Torque Pro (at 77 mph, no idea why it dropped from 17.5 two days earlier). I also confirmed the Torque Pro reading by calculating miles driven/gal to fill - same result.
Then I drove at different speeds for about 10 miles at a time, with the cruise set, to see how it affects mpg:
- 68 mph = 18.3 mpg
- 73 mph = 16.6 mpg
- 76 mph = 16.9 mpg.
A bit odd that 76 mph gave better mpg than 73 mph, but I may be splitting hairs.
Next is where it gets interesting. I made a stop of an hour, then headed home. I was in traffic, going about 60, and noticed that Torque Pro was reading about 24 mpg. That sort of made sense, I figured slower speed = better mpg. Then traffic sped up, and at 65 mph I was still showing 24 mpg. We sped up to 75, same reading.
By the time I got home, I put on 40 miles of about 1/3 60-65 mph, 1/3 70-75 mph, and 1/3 stop and go traffic.
And this averaged out to the 25.3 mpg you saw above. How is that possible? How can combined freeway and stop and go traffic be better than freeway only?
To review my trip over the past few days (and why I think my truck is bipolar):
- First 100 miles = 15.3 mpg (mostly 70 mph), which obviously I wasn't happy with (this was measured by miles driven / gal to fill, realizing that there's always some error in when the pump stops).
- Next 225 miles = 17.5 mpg (about half freeway at 70 mph, half back roads with stop lights, about 60 mph)
- Next 160 miles = 17.5 mpg (all at 75 mph, cruise set).
This is when I read this thread and decided to use Torque Pro to pay closer attention (until then I thought this was normal for our trucks).
- Next 160 miles = 16 mpg according to Torque Pro (at 77 mph, no idea why it dropped from 17.5 two days earlier). I also confirmed the Torque Pro reading by calculating miles driven/gal to fill - same result.
Then I drove at different speeds for about 10 miles at a time, with the cruise set, to see how it affects mpg:
- 68 mph = 18.3 mpg
- 73 mph = 16.6 mpg
- 76 mph = 16.9 mpg.
A bit odd that 76 mph gave better mpg than 73 mph, but I may be splitting hairs.
Next is where it gets interesting. I made a stop of an hour, then headed home. I was in traffic, going about 60, and noticed that Torque Pro was reading about 24 mpg. That sort of made sense, I figured slower speed = better mpg. Then traffic sped up, and at 65 mph I was still showing 24 mpg. We sped up to 75, same reading.
By the time I got home, I put on 40 miles of about 1/3 60-65 mph, 1/3 70-75 mph, and 1/3 stop and go traffic.
And this averaged out to the 25.3 mpg you saw above. How is that possible? How can combined freeway and stop and go traffic be better than freeway only?
calimobber
Member
The one thing no one talks about is elevation. It plays a HUGE impact on mileage. When I was living in Grand Lake,CO at 9k and driving to hike peaks I almost always got over 20mpg. My power was shit and it felt like a turd but mileage was good.
Now im below sea level and I get 17-18mpg driving 65mpg. I thought something happened until I drove to utah and mileage jumped back up.
The more air oxygen the more fuel used to achieve the proper mixture.... The less oxygen( higher elevation) the less fuel used. :first:
And everyone know those inflated numbers 24mpg+ are either not real or you worked really hard to get those and it was prob flat or down hill.
Now im below sea level and I get 17-18mpg driving 65mpg. I thought something happened until I drove to utah and mileage jumped back up.
The more air oxygen the more fuel used to achieve the proper mixture.... The less oxygen( higher elevation) the less fuel used. :first:
And everyone know those inflated numbers 24mpg+ are either not real or you worked really hard to get those and it was prob flat or down hill.
TejasRunner01
New member
Well I'm happy where this thread has gone for the most part. If it helps I've been driving in Texas on some decently flat roads with 33 psi in the tires. Truck rides straight and true after the alignment. My toe in was .33 on the old tires before the alignment : ( now it is. 03 on each side
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4Runner4Leon
Senior Member
So no one wants to take a crack at my crazy results?
IBallEngineer
New member
Yes, they are crazy. :der:
4Runner4Leon
Senior Member
The part that's not crazy is that the mpg readings were confirmed with gallons needed to fill.
So aside from planning to clean the MAF today, I'm scratching my head as to what could cause the same vehicle to go from 16-17 at highway speeds to 25 mpg combined highway/city in the same day? The only difference I could think of was that the air temp went from around 50F to around 80F.
I also have the distinct impression (confirmed by the mpg readings) that the change occurs from trip to trip, and is consistent on a given trip. i.e. the mpg is either good or bad for the duration of each trip.
Can something be "sticking" if you will, so that on some drives it causes the mpg to be higher than on others? I'm thinking back to carburetor equipped cars, but can't really think of any equivalent on fuel injection.
19963.4lsr5
New member
When it isn't 20 degrees outside I will regularly get 23mpg on my rural 2 lane 32 miles each way to work. None of its is flat. I'm going up a hill or down a hill or dodging a horse and buggy or stopping at one of the 15 red lights on my way to work. But highway at 70mph is 19-21mpg.
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calimobber
Member
I know people are prob getting annoyed we keep feeding this kinda post but......No nothing is special about those numbers. We see these post every so often. If you keep seeing these numbers, keep a log and update us after multiple fill up and trips.
There is no magic trick to get 25mpg or everyone would have done it by now.
4Runner4Leon
Senior Member
I'm actually not feeding the "over 24 mpg" line, I was one of the skeptics at the outset. It's just that after paying closer attention to my mpg, I'm seeing a variability that I simply can't explain.
I agree that trying to get mpg from a single fill-up can lead to a lot of error (see another poster who just calculated 28 mpg from one fill-up). So I think I'll do what you suggested and keep a longer log of my fill-ups and miles driven, and come up with a more longterm answer. I don't expect 25 mpg, I'll be happy to settle for 20+.
IBallEngineer
New member
4Runner4Leon
Senior Member
Interesting read, thanks. So that may account for about 1-2%, but I'm seeing changes of more like 30-50%.
What about the intake air temp effect? As I was recreating the last few fillups in my head, I noticed a strong correlation between ambient temps and the gas mileage, as follows:
Air temp mpg
40F 15.3
60F 17.5
50F 16
80F 23-25
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TonyB66
New member
There's a forum focused on fuel efficiency that addresses all aspects from aero, weight, environmental factors, gassing-up, instrumentation, calibration, driving style...
Fuel Economy, Hypermiling, EcoModding News and Forum - Ecomodder.com Fuel Economy Forum
I did a bit of searching there, albeit quick, and I found 2nd gen posts only.
I had posted there years ago regarding my MINI Cooper, and they were quite helpful with SC2 questions. In setting-up my MINI for some track days, it had become quite fuel efficient, when driven with that goal in-mind...
Might be worth starting a thread there on our 3rd gens, if one doesn't already exist; and then share here of course.
A "Jeff88" there has in his profile what looks to be a 90-day rolling average of 19.78 mpg in a 99 Toyota 4Runner SR5 Highlander.
This post seems to reflect that 22-25 is indeed doable:
http://ecomodder.com/forum/showthread.php/aero-modding-4runner-27153-4.html#post410122
Fuel Economy, Hypermiling, EcoModding News and Forum - Ecomodder.com Fuel Economy Forum
I did a bit of searching there, albeit quick, and I found 2nd gen posts only.
I had posted there years ago regarding my MINI Cooper, and they were quite helpful with SC2 questions. In setting-up my MINI for some track days, it had become quite fuel efficient, when driven with that goal in-mind...
Might be worth starting a thread there on our 3rd gens, if one doesn't already exist; and then share here of course.
A "Jeff88" there has in his profile what looks to be a 90-day rolling average of 19.78 mpg in a 99 Toyota 4Runner SR5 Highlander.
This post seems to reflect that 22-25 is indeed doable:
http://ecomodder.com/forum/showthread.php/aero-modding-4runner-27153-4.html#post410122
Last edited:
19963.4lsr5
New member
I pay close attention to the milage on my 2002 Saturn SL1. Temp and warmup time have a lot to do with it. Plus the winter time has much colder dense air and usually is associated with a high barometer in the winter.
My Saturn will get as low as 38mpg for a 400+ mile tank driving it for work when highs are in the low 20's and lows are below 0. And in the heat of summer I average 45-46mpg for the same drive and can easily go 480 miles on a tank for work.
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4Runner4Leon
Senior Member
That's interesting data, I found similar stories just from a brief internet search. But those (like yours) are for a difference of maybe 100F between hot and cold, my readings above are over a much narrower range. I just can't believe that 30-40F change in temp would cause that much of an effect, but the correlation is intriguing (or a fluke).
Something I read online suggested that if the ECU is improperly reading the intake air temp, it may richen the mixture too much, thus reducing gas mileage. I haven't researched this any further yet.
19963.4lsr5
New member
The checks and balances is the O2 sensor before the CAT. (The closed loop operation)
All the sensors (including TPS) input their data to the PCM/ECU. Based on those inputs the ECU picks a fuel map for those operating conditions. And in a perfect world you would have a 0 in the STFT and a 0 in the LTFT.
But the world isn't perfect so the O2 sensor reads the oxygen content of the exhaust and tweaks the fuel trims. That tweaking of the fuel trim shows up on your STFT (short term fuel trim) and LTFT (long term fuel trim). And it actually looks like this trim wise. LTFT.STFT so if your LTFT is near zero than its picked the proper map based on current inputs. The LTFT number tells you the overall health of the engine and fuel management system.
So if any sensor is off the O2 sensor will detect the richer or leaner mixture and act accordingly by adding or removing fuel. One check I do often is look at the ECT and IAT temp and make sure they are very close to each other as well as reading current ambient temp before a cold start where the vehicle has sat at least 8 hours.
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All the sensors (including TPS) input their data to the PCM/ECU. Based on those inputs the ECU picks a fuel map for those operating conditions. And in a perfect world you would have a 0 in the STFT and a 0 in the LTFT.
But the world isn't perfect so the O2 sensor reads the oxygen content of the exhaust and tweaks the fuel trims. That tweaking of the fuel trim shows up on your STFT (short term fuel trim) and LTFT (long term fuel trim). And it actually looks like this trim wise. LTFT.STFT so if your LTFT is near zero than its picked the proper map based on current inputs. The LTFT number tells you the overall health of the engine and fuel management system.
So if any sensor is off the O2 sensor will detect the richer or leaner mixture and act accordingly by adding or removing fuel. One check I do often is look at the ECT and IAT temp and make sure they are very close to each other as well as reading current ambient temp before a cold start where the vehicle has sat at least 8 hours.
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Tyler James Inc
Senior Member
Me too [emoji23]
I have something to add: rev the piss outta her- she loves that shít!!
I started shifting at 2800 instead of 2200, and I went from an average of 15mpg to an average of 17mpg! Been consistent the last 4 fill ups. I've calculated the last 12k miles, so it's not just a random inconsistent number.
That's on 315/70R17 on 17x9 wheels with 4.10's.
I have a Tacoma VSS, and my speedo is dead on.
19.8mpg was the best I've gotten on a trip, and there was a LOT of 4k rpm hill climbing on that tank. I'm telling you guys, high RPMs save lives. And gallons.
