Hi Scotty,
I have a 2007 Prius with 127000 miles and live in Mn. Car runs good but has a rough idle once in a while, then usually clears up in few minutes. Now during winter, i am getting 17 mpg less than summer. 48 down to 31. This happened last winter too. Never had a code in 2.5 years. New battery pack installed by Toyota almost 3 years ago Help!!
You can find tips for improving your vehicle's fuel economy in our Frequently Asked Questions, posted at the top of the home page.
It is a 12 year old engine that has some wear on it. Aside from what @mmj recommended, realize that fuel mileage will go down with the winter blend fuel available, the engine compression is down significantly from what it used to be and aging fuel injectors and other fuel system parts just aren't what they used to be. Have you changed the PCV valve with each oil change and made sure the tires are properly inflated (see the driver's door jamb sticker) and aligned? When was the transmission fluid and filter serviced last. There are many things that contribute to gas mileage figures.
winter gas explanation: https://carkiller.com/scottykilmer/qa/2011-rav4-runs-less-well-on-njs-winter-gas/
about a month ago I bought a used 2018 Honda Civic from Enterprise. Since then the mileage has gradually dropped from 40 mpg to 36 mpg (recently the weather has been very cold and mpg has been falling faster). Is this normal?
Every winter I experience up to an 8% drop in fuel economy (I keep a spreadsheet).
When driving at 130 km/h (80 mph); car sits at 4,100 rpm.
Try driving at a more sane speed? Fuel economy ratings are generically set around 60-65 MPH. If you're doing 80, you're burning close to 2x what you would going 60.
The fuel filter was changed last year. Could it be the fuel pump or injectors needing replacement?
No. If the car is going that fast and feels like it has power, there is nothing wrong with the fuel system. It takes a lot of fuel to go fast.
First try the cleaner if that fixes it great. If not, you might try a new maf sensor when that sensor goes bad it will also get bad gas mileage
(...) plugs or injectors. Not something I can afford to do (...) Is the mpg about right for this car?
https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=22494
According to the EPA the expected MPG for an '06 Ford Escape 4WD (3.0L V6 AT) is 17 CITY/ 21 HWY.
14 MPG is a bit low - reset fuel economy and try driving it conservatively maybe it's the driving style.
Try connecting a scanner and looking at the fuel trims and other data that's not within the expected range.
Also, this might help:
https://www.youtube.com/watch?v=NWCKvU2FmDc
You seem more knowledgeable than me, so I'll just ask the "idiot" questions that you've checked the basics like air filter, MAF, fuel filter (external one and one on the fuel pump if it has it) and the injectors?.
Also have you gone over to Ethanol fuel?.
The most useful and immediate information would come from a scan tool that has Live Data capabilities. More specifically, both Long Term and Short Term Fuel numbers would tell us if the vehicle is running excessively lean or rich. (Anything over 10 percent plus or minus, particularly with the Long Term Fuel Trim indicates trouble ahead. The Short Term number fluctuates constantly).
You might have a dirty Mass Air Flow sensor. You might have, as stated above, a dirty throttle body. It's easy and cheap to clean these.
If the vehicle is running "rich," because these two are dirty, then you'd want to attend to them promptly. A rich fuel mix will shorten the life of your catalytic converter and your engine.
I have a 2015 Toyota Camry SE I4 with 116000 miles on it. For a while, I was average about 32mpg. But now, Im only getting 25mpg. I
maybe they changed the gasoline blend
Interesting. I'll have to start going to a different gas station. Thank you.
it won't help if they're all using winter blend, or even buying their gas from the same source.
I bought the vehicle in September and gas mileage was in the 30s at the time. Ive seen the decrease over the course of the last month
Normal in cold winter weather. (If you're in an area that experiences cold winters.)
Fuel formulas aren't the same all year-round. Winter-blend is the unavoidable reason for crummy gas mileage in the winter. There's lot's of info out there on the subject.
This has been answered multiple times. The winter blend of fuel and the cold temperature significantly changes the fuel economy of the ICE, all other things being equal.
ok
I have a clogged catalytic converter... in the winter, with the same driving dynamics, I get 13L/100kms. I was wondering if the catalytic converter could be the reason this is happening?
Likely the converter has gotten more clogged. An engine is basically an air pump, air-in, air-out, and you have a restriction in the exhaust. Get the cat replaced and then see what your mileages does.
Also, it's winter, fuel mileage decreases in winter due to different winter fuel.
Thank you very much, I'll do that!
Winter blend gas can easily account for a drop of 15-20% in fuel economy.
I not familiar with cars...but will a engine flush help my issue?? And as I'm asking..im not sure what happens when you flush out your engine
Find out when gas stations switch in your area and wait for gas to transition to summer blend gas, you'll probably find it's back to where you think your mileage should be after a few fill ups.
Okay..thank you
My checklist would include (not necessarily in order):
*Cleaning the mass airflow sensor
*You mentioned the air filter, look through it and make sure you see light... Maybe clean the throttle body if its easy to access.
*You mentioned oil - Change every 5k, not 10k
*Tire wear and inflation (setting cold temperatures to what is recommended, not a pound more - Check EVERY time the weather changes temperatures too)
*Using good gas with detergents like Techron (PEA). If your gas choices are limited, maybe get a Berryman's B12 or Gasoline Extreme by Hot Shot's.
*Transmission fluid changes are good at 60k US MILES, maybe sooner.
*Check your coolant/thermostat as an engine too cold or too hot isn't as efficient.
*Drive like a grandma and let everybody pass you 
As an aside, I use an Android app called Car Scanner Pro and a bluetooth dongle where I can monitor the fuel/air mix along with engine and transmission temperatures... Even tire pressure and tire temperatures on some of my cars. Maybe a brake is dragging or something, you'll see a temperature difference... Allow for the wheel closest to the engine or transmission to run 3-4 degrees (F) higher. and your FWD wheels will be hotter overall than the rear wheels.
My 2014 Honda Accord MPG dropped significantly. It has 100K mileage.
Start with simple stuff: Clean air filter, good tire pressure, run some fuel injector cleaners. When did you change the spark plugs? Also, when did you adjust the valves?
It gets about 11 l/100 km (21 mpg)
How much are you expecting, at that speed?
Is your vehicle tuned up according to the maintenance schedule?
Are your cold tyre pressures correct?
See here for more tips -
You could see about a 2% or more drop in economy with winter blend gasoline.
my mileage has dropped from 27.5mpg average to 23.9mpg
We're into October and gas stations have switched over to winter-blend gas. It is not as efficient as summer-blend, and your drop is pretty much spot on. With big temperature swings make sure you're checking your tire pressures. Lower tire pressure will also effect your mileage.
I'm very OCD about my maintenance. I check my tires twice/week. I always keep them 3psi over recommended pressure cold. So, rolling resistance isn't an issue. It seems as if I didn't have an MPG drop last winter. Only after I ran Chevron Techron through it did I notice the difference. And that was at the beginning of September, before they switched to winter blends.
1. Are your cold tyre pressures good?
2. Is your air filter clean/new?
3. When was the last time your throttle body was cleaned?
4. Do you change your oil regularly?
5. Do you have a sedate driving style?
6. Any codes?
7. Any aftermarket parts fitted?
8. https://carkiller.com/scottykilmer/qa/poor-gas-mileage/#post-27185
1. yes
2. yes
3. no idea, just got the car.
4. it was just done before I bought the car a month ago.
5. yes
6. no
7. no
As @geriscan mentioned, clean your throttle body & MAF sensor using Scotty’s video as a guide. Also, try & look for the tC’s forum online & verify if the others on there are getting any better gas mileage than you are. Oh also, when you’re on a flat road (preferable empty), try & shift into neutral and watch the car’s behaviour. It should coast smoothly & gradually begin to lose speed. If it abruptly starts to slow down, it means your brakes are dragging and that could certainly affect fuel consumption. Keep us updated. Good luck.
I recently bought this 2016 Scion TC. It's fine except I only get 23 mpg's average
What's in the car? meaning, is trunk and back seats empty or are you hauling around unnecessary added weight?
Also, are you in a part of the country where it's still cold? If so winter blend gas gives lousy gas mileage. Once summer blend is available you should get better mpgs.
Nothing/ no
nope
I recently bought this 2016 Scion TC. It's fine except I only get 23 mpg's average
During the months here when gas is winter-blend my mpg's go down a few to about 25, and during warm weather when gas at the pumps is summer-blend my mpg's goes up to about 28+ and this is driving a 2019 V8 Camaro SS. Here in NC the switch over is mid-May and mid-October.
So your tC is 5 yrs. old with 38k miles. Hasn't been driven much over the 5 yrs. that's 7600 miles per year or 633 miles per month. That's not much, so it's been used to being driven very little and short trips. Also, don't go by what the mpg's the car says, there's quite a bit of error margin. I calculate at each fill up and reset my trip A each time to figure real mpg's.
One thing the 23/31, is under ideal conditions and the best numbers that were returned during testing to report to the gov. However; you should be getting better than 23 mpg's. Avg. combined real world is probably more like 26. Heck, I'm getting better mpg's with my V8 muscle car, so something is holding it back or may just be the way your particular tC runs. But it is at a point to be changing the trans fluid, and consider cleaning the MAF, throttle body plates, change fuel filter, have injectors checked out. How much you want to do to get a few more mpg's. Shoot, you might also just need to take it on a longer trip and "air it out".
You'll need more information. If you have a scan tool, use it, and see if there are any general OBD II codes or any Mode 6 (Enhanced Diagnostics) measures that are out of spec. If you don't have a scan tool, either find a good diagnostic mechanic, and pay them to do the diagnosis with an upper-end scan tool, like the Thinkcar that Scotty uses.
why my car 17 Lincoln MKZ awd 2.0 ecoboost suddenly has went from 450 to 470 miles per fill up to only 350 miles on a fill up.
This may sound nutty but the first spate of cold weather can do weird things to batteries that are marginal to begin with. Have your battery load tested and also your alternator output. The major auto parts stores will do this for free.
Battery is literally less then a year old and was replaced at the Ford dealer only thing I could think is the cold like yu said maybe affecting fuel, also I ran an injector cleaner from gum out a couple oil changes ago, and last week I did a bg service of 44k on it
Is your air filter new/clean?
What cold tyre pressures are you maintaining?
Have you recently started driving a lot in bumper to bumper traffic?
What’s the mileage on a 3-4hr relaxed highway drive?
The air filter is clean and my tire pressures are checked daily cold and set to the recommendation on the door which is 34 psi cold. Run 91 octane as that’s the best we get in Colorado, the mileage seems to slowly be returning as I filled up initially today before work. And got a reading of 399 to empty went about my day on my way back I was a little over a half tank I stopped to top off and got a reading of 417 to empty currently on course to get 400 outta the tank as the numbers currently show, I recently had the vehicle scanned at Ford cause I could not figure out how to get the electronic parking brake system to stop throwing a fault to the abs module causing the most annoying ding constantly. He scanned and found the right rear was open. Meaning not getting a connection, I checked it when I got home and sure enough the plug was not securely seated clicked it in problem solved 🤦🏽♂️🤦🏽♂️🤦🏽♂️
So the right rear brake was sticking?
Poor Gas Mileage (Honda Civic)
I answered a similar question recently. I'm adapting from that answer, below:
_
The 02 sensor readings might have been a cause, or they might well be a symptom. As an effect, a symptom, I'm assuming that the Long Term Fuel Trim (something that can be measured with a scan tool with Live Data capabilities) is in the positive, by over 10 perccent. The control module is adding fuel, so the Civic has been running lean. You could smoke test the vehicle, looking for any and all vacuum leaks. Even a tiny pinpoint hole between the engine and the exhaust pipes would bring in unmetered air, and the engine would run lean (which means that the control module will add fuel, reducing fuel efficiency).
In the same thread, Doc's suggestion was good. Check the injectors. An injector that is dripping gas, rather than spraying it, will throw the control module off. (An injector head that is leaking will look cleaner than injectors that are working properly).
And there's always cleaning the throttle body and the MAF sensor. If the MAF sensor is dirty, i will mismeasure the air flowing into the engine. Scotty has a video "How to Make Your Engine Run Better with Some Spray Cleaner.") On most vehicles, like my 08 Camry, it's easy and relatively quick to clean the Mass Air Flow sensor and the Throttle Body.
You don't need a mechanic to clean these two items, and the two cans of spray are relatively cheap, at least here in the U.S.
__
Finally, don't throw any more parts at the issue UNTIL you have an accurate diagnosis. You'll run out of money before you'll solve the issue,
Thank you! It turned out to be my Oxygen Sensor working inefficiently however not enough to trip the code... I replaced the Air/Fuel Ratio sensor first... and that was $160.. but the Oxygen Sensor in the exhaust manifold area (?) was only $68.. and it completely fixed my Long term fuel trim from plus 8% to 0.0% to 1.3% give or take. (unless I'm idling a lot.. I'm up in Canada here so the car idles the odd time in the winter to keep the vehicle warm)
Thank you everyone for your input.
Have your Catalytic Converter checked to see if it needs cleaning or a replacement. Make sure that your oxygen sensors are in good condition. Make sure that you MAF Sensor, Throttle Body, Air Filter, Cabin Air Filter are clean. Use the recommended octane level of gas for your car and make sure that it is a "Top Tier" Gas brand in order to burn clean and efficiently. Check your engine for sludge and carbon build up. If possible use a fuel injector cleaner that has "P.E.A." to clean your carbon. A.T.S. is recommended, but it is powerful...so use it maybe one or two times a year to prevent damage to your engine seals. A regular fuel injection cleaner with "P.E.A." such as Gumont or Techtron is fine, providing that you use it correctly every 5 or so gas fill ups. (Not every fill up because it's too much) Gas is gas but some gas brands can be better and use better and more detergents to keep your car clean and help with your Cat Converter. (Some gas stations in New York and New Jersey like "GETTY GAS" got in trouble in 2008 because they were putting water in their gas.) Use a good oil that is recommended for your car along with a premium oil filter. All these things can help with the exhaust and emissions of your car to run better and prevent the Cat from clogging. Scotty has a video on cleaning a Catalytic Converter. Otherwise, it's very expensive to purchase one. It's also good to check your cars exhaust in colder weather to see if condensation (water) comes out of your tal pipe. That's a good sign of a good Cat and Emissions.
https://clark.com/cars/top-tier-gas-stations-clean-engine-aaa/
https://casetext.com/case/kara-holding-corp-v-getty-petroleum-marketing-3
https://www.nbcnews.com/business/consumer/watered-down-gas-way-more-common-you-may-think-n776016
THANK YOU!!!
I have a 2017 Toyota Highlander LTE.... slowly and surely my mileage has gotten lower and lower on a full tank where now it sits at 270 on a full tank.
Normal wear on the engine, lower compression, less efficient and winter gasoline blend all contribute to lower MPG. How have you been maintaining the vehicle? Regular oil and filter changes (5000 miles), transmission fluid and filter (30,000 miles), differential and driveshaft lubrication, clean MAF, spark plugs, air filter, etc?
I have kept up with the maintenance of the vehicle but the only thing I havent changed is the spark plugs...do you think that really could affect why my total miles wuld drop about 60 miles on a full tank??