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What can be the causes of poor mpg (20-22) and no engine light activation?

4K views 78 replies 22 participants last post by  Turbocat9000 
#1 · (Edited)
I previously posted about great mpg in my 2019 Camry SE, but in the past four months of city >> highway driving it seems the car is getting 20-22 mpg. It runs fine. No discolored exhaust. No shaky engine. No engine light. When listening to the Gail pipe exhaust, there might be a faint recurrent clicking. I could post the MP3 audio here.

A gas station mechanic said it could be the mass air or air mass detector or the air to fuel ratio sensor.

I went to a Toyota dealership and the service manager said unless the engine light is on, I would be wasting $400 to check for what's wrong.

How to approach this problem? Anything I can do myself?
 
#3 ·
If you are in a northern state- winter driving will significantly lower mpg. The lower the outside temperature, the lower your mpg- as the engine has to work harder to warm up and keep the cabin at the set temperature.

20-22mpg in the city isn't great for a Camry with the four cylinder engine- but it's entirely possible if you live in a northern state and are dealing with below-freezing temperatures right now during winter... especially if you are doing lots of shorter trips in the city vs longer highway drives.
 
#4 ·
#6 ·
The cheaper code readers do not read live data. Check the manufacturers product description. Yes, it can get overwhelming at first but it is a good diagnostic tool for checking the various engine fuel and vacuum components. It can still be a PIA to identify the culprit component but you can feel more confident taking it to a shop to fix the problem.
 
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#8 ·
I have a 2022 V6 and I am averaging around 27 on a weekly basis so I think something is amiss.....
 
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#10 ·
While there is a difference in winter and summer fuel mixes, I'm not sure it's enough for THAT much of a difference in MPGs. I've only had my '21 LE for a little over a month, but my mileage is listed in my signature, all on winter blend so far, about 75% highway mileage.
 
#11 ·
Tires inflated to 36. I drive always in accordance with the ECO light. The decrease in mpg started before it got cold here, but cold = 40 degrees F here in the SF Bay Area.
Take time to warm the engine before driving on the freeway. That doesn't take very long. A cold engine gets bad mpg. Short trips don't help. Lead-footing on winter gas gets bad mpg. Observe the engine temp gauge to verify when it gets to operating temperature. If you zoom out the freeway in this cold, the air may overcome the engine thermostatic temperature control.
 
#17 ·
One common to fail and inexpensive part is the coolant temp SENSOR (ie: not the sender for the dash gauge but the one that speaks to the ECU). The things fail in many different ways, but just a minor failure can tell the ecu that the engine is not fully warmed up and that will make the ecu set the fuel mix a bit rich, killing fuel mileage. Easy to replace, but they can be tested as well, using a temp chart and resistance scale and hot water.
 
#19 ·
How specifically to do this test? Any links?

how many miles ago? & what about all the other stuff. If your car’s around 100k miles or more then it needs a major service
If you are in a northern state- winter driving will significantly lower mpg. The lower the outside temperature, the lower your mpg- as the engine has to work harder to warm up and keep the cabin at the set temperature.

20-22mpg in the city isn't great for a Camry with the four cylinder engine- but it's entirely possible if you live in a northern state and are dealing with below-freezing temperatures right now during winter... especially if you are doing lots of shorter trips in the city vs longer highway drives.

Tomorrow the wi-fi OBD should arrive and will try to get that data. If I post its here, will you know how to interpret it?

Ahh yet another mpg thread. Nothing wrong with the car as others said they get similar mpg. Leave it's alone.
how many miles ago? & what about all the other stuff. If your car’s around 100k miles or more then it needs a major service

Ooops. last service was on 3/25/2022 when the mileage was 39,920. Service included new Amsoil synthetic 0-16, new OF, new plugs, etc. Today the mileage is 42,600. Do I need to get the car serviced. now again?
 
#18 ·
Yes, coolant temp sensor and the mechanical thermostat, either can cause high fuel consumption without ever generating any codes or engine light!

Also, as 98camryLE mentioned, shorter trips (meaning that a high percentage of driving is done with a colder engine, which similarly kills the efficiency).

Toyota and I both agree it's best not to try "warming up" the engine before driving, it warms up much quicker while driving, so uses less fuel overall.
Drive gently during warmup (heck, maybe all the time, like me and the other older drivers here!).
My car is a mostly highway-driven 2015 Camry LE and my average mpg over the past year (4300 miles to date) is 35.2mpg without having ever reset the avg mpg during this time. I usually do not use a car for short trips though, I prefer "hoofing" it up to 6 miles round trips and cycling many 5 to 45 mile round trips (made possible by California foothills weather and road conditions).
 
#20 · (Edited)
Ooops. last service was on 3/25/2022 when the mileage was 39,920. Service included new Amsoil synthetic 0-16, new OF, new plugs, etc. Today the mileage is 42,600. Do I need to get the car serviced. now again?
Your oil is fine as far as mileage, but in my car I like to change it out every 5 to 6 months if I have not hit the mileage where I change it out. You got almost a year on that oil and filter. Should not need service on anything else. Hopefully, you can change your own oil so you are saving money. It would not have anything to do with your mpg issue.

But as others have stated, The first thing I would do would be to hook up my OBDII reader and look at my live data. Buying one is cheaper than what it would cost you to go to any local shop and have them hook theirs up and look at the numbers for you. This is the one I use, it is pretty basic, not super fancy but it does have live data and can read your fuel trims. The OBDII can get kind of complicated, they can do a lot of things, but you do not need to know how to do all those things, you can learn them one at a time. For your fuel trims, it is pretty easy. Hook up the reader to the port, allow it to connect to your system, start your car up and let it idle, on the obd, go to live data and just scroll down to your fuel trims. There will be long-term LTFT which is your average fuel trim over time and there will be STFT which is your current fuel trim numbers. Just look at the STFT and observe the number next to it. A negative number indicates the computer is holding back fuel from the injectors and a positive number is a computer adding fuel to the injectors. What you really want is a STFT of 0.0, that would be perfect, but you rarely see that. In my Lexus, I believe the normal acceptable range is +10 to -10. If you see a STFT number over 10, lets say +26 or something like that, This could indicate something like a leaky or loose vacuum hose. If the number looks good then you can at least rule this out as a cause of the MPG issue. If it is an issue as some have stated that it is normal for your car to get those numbers.

As for someone mentioning, asking if your trans is going into overdrive, it is just the high gear. So lets say you are cruising down the hwy at 60mph, what is your RPM gauge reading? If your trans is not going into the high gear and staying a gear lower, it is going to be running at a higher RMP and eating up more fuel. I do not know what the normal RMP at highway speed is for your car but others here have the same vehicle and can tell you if it is normal, for instance, my lexus at highway speed is right at 2,000RPM, If I was not in OD and accidently left the gear shift in 4 rather than D I would be at like 3000RPM or there about. And that would be eating up my fuel. Some vehicles you could be out of OD and not even notice if you are not paying attention and you would not get any kind of engine light for that.

 
#21 ·
Your oil is fine as far as mileage, but in my car I like to change it out every 5 to 6 months if I have not hit the mileage where I change it out. You got almost a year on that oil and filter. Should not need service on anything else. Hopefully, you can change your own oil so you are saving money. It would not have anything to do with your mpg issue.

But as others have stated, The first thing I would do would be to hook up my OBDII reader and look at my live data. Buying one is cheaper than what it would cost you to go to any local shop and have them hook theirs up and look at the numbers for you. This is the one I use, it is pretty basic, not super fancy but it does have live data and can read your fuel trims. The OBDII can get kind of complicated, they can do a lot of things, but you do not need to know how to do all those things, you can learn them one at a time. For your fuel trims, it is pretty easy. Hook up the reader to the port, allow it to connect to your system, start your car up and let it idle, on the obd, go to live data and just scroll down to your fuel trims. There will be long-term LTFT which is your average fuel trim over time and there will be STFT which is your current fuel trim numbers. Just look at the STFT and observe the number next to it. A negative number indicates the computer is holding back fuel from the injectors and a positive number is a computer adding fuel to the injectors. What you really want is a STFT of 0.0, that would be perfect, but you rarely see that. In my Lexus, I believe the normal acceptable range is +10 to -10. If you see a STFT number over 10, lets say +26 or something like that, This could indicate something like a leaky or loose vacuum hose. If the number looks good then you can at least rule this out as a cause of the MPG issue. If it is an issue as some have stated that it is normal for your car to get those numbers.

As for someone mentioning, asking if your trans is going into overdrive, it is just the high gear. So lets say you are cruising down the hwy at 60mph, what is your RPM gauge reading? If your trans is not going into the high gear and staying a gear lower, it is going to be running at a higher RMP and eating up more fuel. I do not know what the normal RMP at highway speed is for your car but others here have the same vehicle and can tell you if it is normal, for instance, my lexus at highway speed is right at 2,000RPM, If I was not in OD and accidently left the gear shift in 4 rather than D I would be at like 3000RPM or there about. And that would be eating up my fuel. Some vehicles you could be out of OD and not even notice if you are not paying attention and you would not get any kind of engine light for that.


Oh my. You get the Answer of the Year Award. Thank you so much. Will test both tomorrow.
 
#23 ·
Fuel trims look ok to me. I do not see anything bad. I am curious about the air intake temp at 131F. What is the ambient air temperature where you have the car? What does the temp read when the car is moving? I am assuming it is maybe sucking up heated air from the engine bay while parked and idling. Unless you have a turbo and intercooler, I believe your air intake temp should be +/- 10F of ambient air temp.
How does the car run, does it have a smooth idle? Does it accelerate normally?
 
#24 ·
Fuel trims look ok to me. I do not see anything bad. I am curious about the air intake temp at 131F. What is the ambient air temperature where you have the car? What does the temp read when the car is moving? I am assuming it is maybe sucking up heated air from the engine bay while parked and idling. Unless you have a turbo and intercooler, I believe your air intake temp should be +/- 10F of ambient air temp.
How does the car run, does it have a smooth idle? Does it accelerate normally?

Good questions, Trucker. That measurement was during ten minutes of stationary idle. Will check the temp tomorrow when moving. No turbo, no cooler. The car has a good idle, but there's clicking heard from the tailpipe. Could post an MP3 here.
 
#33 ·
You need to put the engine under load. Like take the car to a safe area, from a roll great to third and hold it in third and floor it to redline. As far as burning rich, practically every car from the manufacturer will run rich because it's far safer than running lean. This is why modern ECU dump extra fuel when there is a problem.
 
#37 ·
Also look at other things, physical things that can sap your MPG. Check your air filter, is it clean? a dirty filter restricting air flow can really hurt your MPG. Make sure it is clean, and check the air intake system from the front of the car to the air filter to make sure there are no obstructions such as a rodent making a nest.
Take a look at your tires and make sure they have proper pressure.
Look at your brake pads. do they all look about the same thickness/same wear? If you find most look good but one set is very low, you may have a brake caliper that hangs up causing extra drag on that wheel.
I would hand clean the throttle body and you can pull out your MAF and spray it down with some MAF cleaner, that is good general maint anyway. It would be interesting to see if your throttle position number on your obd drops after cleaning your throttle body and MAF.
Maybe a bottle of Techron fuel system cleaner in the tank on your next fill up.
Also confirm what your RMP is when you are cruising down the road at 55, 60mph or whatever to rule out the theory about your car not running in the proper gear.

Others here said that that is normal MPG for winter driving in that car. Where do you live, what are the winter conditions like where you are? And have you had this car long enough to have driven it the same time last year? if so, do you remember what kind of MPG you were getting then?
 
#39 · (Edited)
Maybe a bottle of Techron fuel system cleaner in the tank on your next fill up.
Absolute waste of money. Gasoline already has enough detergents in it already. If you want to do a BG or Seafoam like cleaning every 50k miles or so that's different. But these engines are multi port engines, meaning it has two different sets of injectors. It keeps the engine pretty clean already. Again and as others have stated, the car is stated at 33mpg combined avg in the best of conditions. Others have stated that's normal mpg for winter. Especially if your doing mostly city driving and shorter drives under 12miles one way. Unless you smell it dumping fuel, just leave the car alone.
 
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