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Discussion Starter #21
I am trying to keep track of my best mpgs so thought I'd not want to waste another thread.

Went from LA to Springs of Willow last Sunday drove almost 250 miles before fill up. My driving style wasn't as I expected as I tried to keep up with RX7 Rotary Turbo while trying not to be late for the event. So, on the way there my average cruising speed at the freeway was about 75-85 mph. Same thing on the way back home. That was my highest mpg, 24.5 mpg. The next highest mpg I see was 24mpg cruising at 65mph to Long Beach from LA. I bet I could do better than 24.5mpg if I cruised at 65mph. Oh well, I'll try another time.
 

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Ugh, second tank today, calculated numbers, came out to 17mpg again. This is mixed suburban driving, i'd expect 19-22 at least!! What is going on!
Check your right foot, this is the key to good fuel mileage. Some people think they got to push their gas pedal all the way down to get going and then come upon a red light and slam brakes on. This will eat gas in any vehicle. Drive easier, gentle starts from a stop and let your car coast up to a red light instead of abrupt stops and I guarantee your fuel mileage will increase. Another tip keep under 70 mph on the highway. No hard accelerating.
 

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gentle starts from a stop
No hard accelerating.
We don't drive carburated cars anymore, that technique is actually wasting gas today. MPI (or DI) are metering the gas/air mixture exactly, no matter of regime (once the O2 sensors are warmed up and system is in closed loop). Accelerating slowly just keeps you more time in the lower gears.
The faster you get in the last gear (fast speed at lower RPM's), with torque converter locked, the better.

The biggest impact in MPG that we can control today is air speed.
And engine friction - use synthetic oil. And align wheels. And maintain brakes so they don't drag.
Personally, if I am at a stoplight that just changed to red, I push the transmission shifter in "N". That way I don't spin oil inside torque converter. I have looked with OBDII and idle consumption drops by 25% compared with idle in "D". There is no need to press the shifter button or to look, transmission manufacturers made that transition linear and stops automatically between N and D.

More:
 

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Toyota Rav4 2008 2.4 ACA33L-ANPGK /Communication through automatic translator, sorry for any errors
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Are we running with regulated valves? The manufacturer provides for inspection and regulation of the valves periodically, and they affect consumption when they are not regulated. My average is 14 mpg in an urban circuit when driving to work. My journey is short, about 15 min and up to 5.1 miles. However, I can easily do 29 mpg on the highway. This car is focused for travel, not much for everyday use and urban traffic.
SoNic67, does it always pay to shift into N at the various stops instead of keeping to D? Will mechanical wear occur that will be more costly than fuel economy? I always receive guidance that the idea is to always keep in D at short stops, like the traffic light, but I am tempted to leave it at N because the motor load decreases noticeably.
 

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IMO the wear of the mechanical linkage is null. I usually do it when I know it will be a longer wait (like after I slow down on yellow and stop at red).
Or in stopped traffic in the summer, and I need
On the other hand, you need to pay a bit of attention, not to press gas pedal in N and, at 2000 rpm, realize that you're till in N and slam into D.

I am doing this for 10 years on my other cars (Ford, Hyundai) and I didn't have any issues. The transmission manufacturers actually provided for this, because the movement between N and D is the only one that is in a straight line and doesn't require pressing of a button. I can be done with one finger. And you can feel the engine relaxing when it doesn't have to move the torque converter in stall mode.
Some TQ have a higher stall torque and those the most energy hungry.
It's up to anyone to decide... if the 25-26% less gas at idle is worth their time.

Newer cars, with newer transmissions can do that automatically. But then, many of them are equipped with full ISG systems.

Engine running, transmission in N, MAF=5.8 g/sec. That's air, gasoline to air is 1:14.7 ratio.
158015


Engine running, transmission in D, foot on brake. MAF= 7.3 g/s.
158016
 

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Another parameter to be analyzed is the engine load. It drops 9% in N. Not coincidentally the vibration that the engine transmits in the cabin drops considerably in N compared to D. It is interesting to keep N in terms of economy, because the exchange procedure is quite simple, it is not tiring. His report of success without problems for so long in this practice is encouraging.
 

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As far as I can understand, the stall stage is a conflict of forces that are not in the same direction. This leads us to think that the N mode preserves the torque converter by reducing this stressful effect. But strangely all this wall does not affect the rpm, even, by its obd2 monitor, in D the rpm is slightly lower than in N, the value is small and I believe to be irrelevant since the rpm undergoes small variations continuously. Taking the opportunity, I see that your engine has not reached the ideal temperature, which I believe to be 190 ºF. Am I right? I say this because it is the temperature that my vehicle stays most of the time, it is rarely above that and rarely the radiator fan is activated.
 

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The idle RPM is controlled by vehicle's ECU, via IAC Valve. It's a set value in the software, and the ECU will control it in a closed loop, based on temperature and other conditions (like if the A/C is on, will go slightly higher). ECU will pull the rpm lower if the engine tries go higher or push higher if the engine wants to go lower.

And yes, that was a quick test, in my driveway, specifically for that post, but it will happen at any time. You can get your own OBDII adapter for Android/iOS phone (eBay, Amazon) and Torque app.
I use an BAFX adapter.
 

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I already use it. Including the Torque Pro app, which has more features. It does not measure the average consumption of the car very well, it is never compatible with the consumption calculated when filling the tank. But I monitor several other features, like the oxygen sensor, which looks strange. Three oxygen sensor options appear to me. I monitor the three and none seems to occupy between 0V and 1V continuously in N as in most combustion cars. When I came across a consumption of 14 mpg in the initial tanks I was scared, I even suspected that the oxygen sensor was having trouble monitoring by the Torque app. Then I saw that this consumption in an urban circuit is normal, and I think the oxygen sensor may be normal.
 

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They might be wide band sensors, even in your 2008 model.
 

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Wow!!
This article is surprising, it looks like an encyclopedia on the subject. I didn't even know that a more modern component like the A / F sensor could replace the conventional oxygen sensor. From the voltage returns I get in the Torque app, everything indicates that my car uses this type of sensor, as it returns voltages different from those between 0V and 1V of the oxygen sensor. The voltages of a sensor exceeded 3V. Given the high fuel consumption in the urban circuit, I always thought that the oxygen sensor with this strange voltage was in trouble and causing excessive fuel consumption, but now I am calm considering what I read in the article.
I will have to read it several times to understand the ways of testing, as it is not as simple as in the conventional oxygen sensor.
Thank you very much for sharing this information!
 
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