Winter not good for mileage...

[gonzobob]

Originally Posted by 14Corolla

For me. When I talk about higher idling. I'm talking about after warming up. My car normally, in warm weather, idles at 700rpm. In the cold, it idles at 1300.

That seems a bit strange. My car idles around 650rpm (according to my Ultragauge) once warmed up and that hasn't changed now that is a bit colder. But we've had only a few days below freezing so far (we've had a very warm Fall) and that may change once the temps drop down to 10F or 20F.

Maybe your car is staying in "cold weather warm-up mode" all the time. I think I'd take it in to the dealer.

[14Corolla]

Originally Posted by trollbait

Do you have a Scangauge or other way to monitor the transmission temperature?

no
post is too short...please expand to 10 characters

[trollbait]

It is possible that the transmission fluid isn't warming up enough, which might lead to faster idling.

[Draigflag]

On this topic, I have a Toyota Yaris (small city car) whilst mine is in the bodyshop. It's a naturally aspirated petrol engine, and despite being very slow, it also drinks like a fish! Barely scraping 30 MPG on these cold winter mornings, the Clio would be doing 54-56 MPG on the same short cold trips, its easy to see why diesel has become so popular now.

Best I had was 51 MPG on a 200 mile trip, but that's still about 15-20 MPG lower than I would get in mine.

[trollbait]

I wouldn't hold small Toyota economy cars up as examples of petrol being poor for fuel efficiency. The Yaris automatic here still only has four speeds.

[Draigflag]

This one has a plonky little 6 speed, not that it's very slick, still quite revvy but I guess I notice it more coming from diesel.

[14Corolla]

I think you might be right on the transmission not heating up.
I've been watching my computer. My normal daily driving isn't much more than 5 miles on one trip.
I've done a couple longer drives. Not real long. Both went up into the Hills. So should hurt mileage? On these, I could see my average MPG on this tank, keep trying to get higher. Results a little higher than I was running. Basically....more response on increased mileage. Keep going, gets better.

I am impressed with the cruise control. In the Hills. When the car goes downhill. It acts the way I would. It automatically shifts into S drive, then B drive, to slow the car.
Due to using the B drive more, (engine brake) in the cold. It does a good job of saving fuel. Increasing mileage. Didn't know this as much in summer. I coasted more in neutral.

[14Corolla]

Keep watching this closely. I think you're right on the transmission and heating up. After driving a while. At 46f, went to neutral. It did go down to 700 rpm. Thinking you are right.
Filled with all Premium this time. First impression is it is doing better for mileage? We'll see. Either way. Wanted to do a full tank of premium now and then. For the cleaning of the injectors, etc. We're expecting just below zero this week.

[14Corolla]

Just got my worst mileage. 29.4 mpg ... Below Zero. Two storms. Oh well.... At least I'm appreciating my car instead of obsessing on mileage.

[gregsfc]

The two vehicles I'm driving currently represent the most extreme I've ever owned as to how the mpg degrades in the winter time.

The good...My 2015 F150XL with a 2.7 liter Ecoboost and 6-speed auto transmission, standard cab, 2wd, short bed with 3.31 rear axle ratio can achieve from tank to tank, for my commute, in warm weather and calm weather, at or about 24.5 mpg; which is stellar for a gas-powered full-size truck; at least 4.5 mpg better than any full sized I've owned or driven at work. In temperatures that hover from 20-32 fahrenheit for the mid-southeast U.S. typical cold snaps, it drops for the commute, maybe .7; meaning it's about a 3% drop in fuel economy.

The bad...My Honda CTX700 motorcycle is an amazing fuel miser. It's mid-sized at around 500 pounds wet curb weight. It's got a 670 cc parallel twin and chain driven with well over 40 hp and 40 peak foot pounds of torque and over 100 mph top speed capability. For that same commute, at the same speeds and conservative riding style as reported for the pickup truck, I can achieve at least 78 mpg in warm calm weather. At those same cold temps as reported for the pickup truck, it'll drop to maybe 69 (if I could stand to ride below freezing for a whole tank full for 29 miles), which works out to at least an 11% drop.

This means that even though the motorcycle is the fuel economy choice by far, summer or winter, due to whatever factors help or hurt fuel economy in cold weather (as we know there are many) the motorcycle drops at least 3 times as much as the pickup truck as percentage calculation. Some may say that most of that degradation may be due to the motorcycle having much higher drag and how that colder air would have a larger effect, but it has to be more than that; maybe how lean the mc is running or something is what I guess, because prior to the motorcycle I owned a 330 cc scooter that I rode the same way and the same route. The scooter didn't drop nearly as much; maybe 5% at most.

One thing I'd look at if the OP has not is possible odometer error induced by the tires. I've had two different sets of tires on the same vehicle wherein the first set induced a 9% optimistic error, and the second set induced only around 1%. If one replaces tires and doesn't know the error on the first set, he or she may not know the difference the two sets has made with respect to an error, but at least one can check the current error, and also besides an odometer error, tires can make a huge difference in a real change in fuel economy; either because of the extra grip of new tires versus worn tires, or just a difference due to design or general roll resistance of each tire. My current motorcycle tires, for instance, has a larger optimistic error, but even accounting for that, I'm getting around 1.5 higher mpg on an average tank in warm weather. In cold weather, the two sets are/were closer together.