Winter: Warm-up car?

Please resolve a dispute between myself and my finance. Being correcton this matter is not a deal breaker for our marriage but I, of course, want to prove that I am right and he is wrong.

In the winter (we live in Medford, MA) and it is cold, should you warm up your car for a few minutes in the morning, after your car has been sitting out in the cold?

My finance says that he doesn’t want to waste the gas spent on letting the car idle to warm up and mentions the effect of idling cars on the environment.

I say that his car is getting worse gas mileage when he drives it cold so there is there is no savings on gas to not warm it up. Plus, by warming it up, we can run the defroster and heat to make life more comfortable for us.

He drive a 2005 Mazda 3 wagon. I do not have a car.

Best for the car is to warm it up only enough to get it drivable. Chances are it will be drivable as soon as started every day of he year except maybe a couple where you live. Next you warm it up by driving at reasonable speeds for maybe a mile. During this time the engine and the suspension, transmission etc. are all warming up to operating temperature. Then you are ready to hit the freeway.

One exception to that is that defroster. If your vision is being compromised by the weather, warm it up, it is not good for the car, but getting in an accident is far worse.

Definitely not minutes, I would say 15-30 seconds or so for the pumps and whatnot to get the fluids moving. After that it’s a matter of driving without stressing the car too much for 5 minutes, it’ll actually warm up faster and more thoroughly that way. Sitting and idling for minutes would likely waste gas and still leave the car only partially warmed.

I warm up my car on cold days, simply so I don’t have to scrape the windshield and freeze my butt off while driving. I understand that it is not optimal for the engine or the environment, sorry. The car does not need to be warmed up and warming it up will probably use more fuel than driving it cold, but the difference is pretty trivial.

I live in the northeast and have always warmed up my cars. My 07 warms up lots faster than any other car I’ve had. It was 32 degrees this morning and the defroster started melting the windshield ice within 1-2 minutes and the rear defroster had cleared the thin layer of ice in just a couple of minutes. Even if it’s not cold outside, I let the idle settle before putting the car in gear. I’ve heard this gives the engine oil a bit of time to circulate. When it’s cold outside, I drive the car no more than 30 mph for the first couple of minutes. Unfortunately, for those who live in New Jersey - it is illegal to warm up your car. (For environmental reasons…sheesh). The amount of gas you use to warm the car up is probably negligible.

All of the preceding posts have had valid advice, but I would add that while a car is idling, it is achieving ZERO miles per gallon, so whatever gas mileage you get while driving with a cold engine is still preferable to zero mpg.

Years ago, cars with a carburetor and a choke needed several minutes of warm-up in order to be truly driveable. Thanks to modern electronic engine management and fuel injection, cars are now driveable within seconds of starting the engine.

On a very cold day, it might be ok to wait for 30 seconds or so, just to be sure that the somewhat thickened motor oil is circulating properly, but on a temperate or cool day, even 30 seconds is too long to idle your car.

The engine (and the transmission!) will warm up much faster if the car is driven conservatively for the first 5 minutes or so after being started, as compared to letting it idle in your driveway.

Incidentally, there should be a section in the Owner’s Manual (the least-read “best-seller” in the world) on this topic. It might be instructive for you and your fiance (or even your finance!) to read the information in that little booklet about warming up the engine.

In general I agree, however:

  • some of us don’t care if we are getting 0 mpg if out feet are warm when we leave.

  • although it is not required, warming up a car with “modern electronic engine management and fuel injection” will not actually hurt anything, so 30 seconds isn’t “too long,” it’s just not necessary. Idling a cold, carbureted gasoline engine is actually worse for the engine.

  • some of us drive diesels that a much happier with a little warm up time.

  • some of us like to have a cup of coffee (or two) while our car warms up.

I believe you, but what is it about cold, carbureted gas engines that makes idling worse for the engine?

Carb’s are not very precise about metering fuel at idle (especially with the choke partially closed), so the tend to dump a lot a excess fuel into the engine. This extra fuel tends to get into the oil, “wash” the lubricating oil off the cylinder walls, and can cause carbon buildup in the engine due to it running “rich.” Fuel injected engines are much better at providing the correct amount of fuel under low load and idle conditions. I would avoid letting a carbureted engine idle for extended periods of time, but a short period of warm-up may be required before they are really drivable (unlike fuel injected that can be driven immediately, if you don’t mind cold feet).

We’ve had this post before. When cars had carburetors, some warmup was necessary to get the engine to run smoothly and allow rapid acceleration onto the freeway without the choke half closed. Fuel injection cars are ready he moment they start. I agree that enough warmup to clear the windshield is needed for safe driving. Several ways to get away quickly and end your argument:

  1. Use 5W30 or 0W30 synthetic oil; it has a pourpoint of -45F, so it will readly circulate to the valve gear, the most vulnerable area.
  2. I use a frost shield on the windshield when parking outside. This flexible shield covers the windshield, and is tucked in by the the 2 front doors.
  3. If you have an outside electrical outlet, use a block heater to pre-warm the engine, so you have heat in the car much quicker. You can also install an electric in-car warmer so the car will be really warm when you get in.

As pointed out, excessive idling is BAD FOR THE CAR, THE ENVIRONMENT, AND YOUR BANK ACCOUNT… With synthetic thin oil the valves are lubed in 15 to 20 seconds! A few years ago EXXON gave out a tape entitled “THE COLD WAR” whcih showed the effect of not using the right oil thickness on car engines. It sold a lot of 0W30 which they were just introducing at that time.

Ahhhh that makes sense. Do you think running through some “carb cleaner” every couple months is helpful to the engine in this case?
I do find a little bit of a warmup helps for driveability with my 85 Cutlass (1 min-ish), but sometimes it’s better than others.

Modern cars don’t need to be warmed up like the carburated cars of old, as others have testified. However, one poster made a valid comment about getting the windshield defrosted, the comment of which also applied to the side windows. I find that it’s far easier to remove ice on the windshield if the glass is heated up some, and if I drive away with the engine still cold I need to be aware and not breath on the inside of the windshield, as my breath will condense on the cold glass and fog it.

For safety’s sake, if you find these conditions apply to you then I think warming the car up some is good. Safety comes first, gas conservation second.

The consensus is right. I might add, merijul, that the reason you shouldn’t warm up idling is that the engine is healthier,“happier”,in a warmed up state, so the quicker you get to that state the better- for the life of the engine. I live in Pa. It hardly ever gets below 0 degrees F. If I lived in Minn, for example- yeah- I’d let car warm up to where heater was blowing hot before getting in it- it’s a free world!

Carb cleaner just cleans the junk out of the carburetor, similar to fuel injection cleaner. I would use it if I thought the carburetor was acting up (short of needing to be rebuilt), but I don’t know that there is much benefit to using it routinely. I would just let the car warm up enough to be drivable, and not worry about it too much. Also, take a look at the choke if it just gives you trouble on cold days.

“If I lived in Minn, for example- yeah- I’d let car warm up to where heater was blowing hot before getting in it- it’s a free world!”

That’s for sure, I spent a few weeks in a hotel in green bay a couple of years ago (-5 to -10F most nights and no place to plug in my diesel). I would start the car every morning, then go eat breakfast in the hotel restaurant (just like everyone else). I’m all for taking care of the engine and the environment, but I’m not going to freeze to death either.

Diesels, at least the big truck ones, can overcool at idle. This is why big trucks used to have shutters in front of the radiator to keep the engine up to operating temperature when idling and in cold weather. I don’t know if this is an issue for Mercedes car diesels, but warming up from stone cold is probably better even if it doesn’t come up to full temperature until you start driving.

Mine won’t overcool, but it does take quite a while to reach temperature; lots of cast iron, oil, and coolant to get up to temperature. It will run at a steady 80C even in sub-zero temperatures, once it finally gets up to temperature. They never fully warm up at an idle, they just don’t burn enough fuel to heat up anytime soon.

A car this new can simply be put into gear and go as soon as it’s started. But if you need to let your windows defrost/deice or if you’d like the interior to be a little bit warm then it’s not like letting the car warm up is going to hurt anything. Don’t let anyone tell you otherwise.

Thanks everyone for your response. I guess I was wrong but I’ll live. This is all good info to know.

Please correct me if I’m wrong…but even if you warm up a car at idle, it’s still a good idea to drive at moderate speeds for several miles…maybe not so much with FWD, but RWD, AWD and FWD as the additional fluids are still pretty thick and “non compliant”. Just because you get heat from the heater and the temp gage is up, doesn’t mean it’s ready for the Indy 500. So my take is; not all cars are created equal when cold.