truelove

i let the car sit until the RPMs drop below 1k. this is a good indication that the engine is warmed up.

you'll notice that when you start the car in cold weather, the RPMs are just slightly above 1k, but after you drive a while and stop the car, they rest at below 1k. i know this is because the engine has warmed up, i just don't know why this happens. any info on this anyone? i also don't know if warming an engine is necessary.

also, there's a poll here too.

mctwin2kman

Nope, just start it and wait a few seconds and then drive off. I use this time to turn on my seat warmers and pick a station on the radio. It is only a few seconds between startup and proper idle so I am off as soon as the car idles normal. And yes it is a waste of gas as the car will warm faster when driven.

trench

All cars do this, it's called "fast idle," and is part of smog regulations for warming up the cat quicker.

Generally, once you start the car, driving it around warms it up as well or better than letting it sit.

Cheers, BT

Tai230K

In the winter it takes longer 1 or 2 min... in the summer i give it 30 seconds..... depends on the weather ...

truelove

okay, thanks. i honestly had no clue whether or not warming up the engine was necessary at all. i'll probably still wait for about 30 seconds before driving off but i won't sit for any longer than that. even articles that tell you that idling and warming up a car is unnecessary advise at least sitting for about 30 seconds to let oil circulate and such.

KWiK

nope, not at all. I figure it's warm enough by the time I get to the end of my driveway.

Tai230K

the way i gauge whether the engine has warmed up enough is usually wait till the needle is pointing under the 1000 rpm mark... when it reaches under 1000 rpm....... i take off

I'm not sure how it is on the 1.8L though...

vadim

> i let the car sit until the RPMs drop below 1k. this is a good
> indication that the engine is warmed up

A good indication of that is when the temperature gauge bar shows nominal value (80-95 C).

However, warming engine at idle does more harm than good, as the idle mode is the worst for the engine.

40-45 seconds is plenty enough, that's what it takes to warm up the cat converter.

Drive off but don't race the engine - this is the safest (and quickest) way to warm it up.

M-B-Michael

Well, I second Vadim's opinion.

All of you should just keep it under 4000 RPM until it is warmed up. That is what is most important.

FWIW... I let my car sit for maybe 15 seconds (as long as it takes for the garage door to open) then I just take it easy (under 3000 RPM - with my automatic) until the temps are up.

They do warm up best when driven.

oggle

30 seconds on my MB. Longer for my older car.

VoyagerDude

Ocasionally sometimes I wait about 45 seconds for the John-Deere-Diesel-Tracktor sound to disappear

MarkL

I let the car sit for about 10-20 seconds when cold. By then, the fast idle on my C240 drops below 1K. However, this does not mean the engine is warm -- you need to check the temp gauge as someone mentioned. Drive moderately until engine gets close to normal temp range.

BTW, fast idle during cold startup is not just for smog reasons. Cars have had fast idles for the last 50-100 years -- that also used to be part of the "choke's" function. Cold engines require a richer fuel mixture, and a slightly faster idle prevents roughness when first starting.

I'm not "that" old, but for those who don't know or remember, cars used to have a manual choke knob that you pulled out when the car was cold. It closed part of the carburetor air intake to allow for a richer mixture and at the same time, moved a cam into position to keep the throttle open more. As the car warmed, you pushed in the knob to set the mixture for normal operation and return the idle to normal speed. Then, cars used an automatic choke mechanism which was similar to a thermostat -- a coiled spring which contracted and expanded in relation to temperature. This took the place of the manual choke knob. Eventually, almost all cars replaced the complex carburetor with fuel injection and computers and voila -- perfection!

Mark08859

Car and Driver stated, awhile back, that with today's modern engines and oils, the average car needs to be warmed up for 30 seconds.

MB-BOB

If the car is stone cold, it cannot "warm up" in 30 seconds.

This is always a fun debate. Me? I turn the key, count to 4 or 5 (once the starter motor noise dies down), put in reverse, back out of garage... go.

Use your dyno mode to see how the oil level instantly drops the second you turn the car over... the car has plenty of oil to coat everything within a second or two.

oggle

I believe we read the same article. They said the 30 seconds was mainly for the engine to become completely lubricated by the oil, which would've mostly settled to the bottom when you don't drive the car for a while.

tberry

i usually wait about a minute or two before i start moving. Then i take it easy on the car (below 40mph) until the temp gauge hit about 90F (i think its F or C) then i feel safe to push the car....sometime when its really cold (under 40F) and I dont wait long enough the car at low speed accel will not get out of 1st gear until u let off and hit the accel again....has anyone experienced this? I also let the car run at about under 40mph for 5min before shutting off the engine (cool down) when pushing hard. yeah i'm paranoid.

Kal Rubinson

Since my car is garaged at both houses, it is rarely really cold. Normally, I take a few seconds before starting off and run it 'conservatively' (under 3000rpm) for the first mile or so.

If, by some chance, it's left outside overnight in deep winter, the conservative stretch extends until the temp gauge gets up to about 80.

fus10n

From previously owning a Porsche 911 and a Bmw m3, I am in a habit of letting the engine warm for at least 2-3minutes as requested via the manuals.

Hence I let my Benz warm for the same amount of time.

Take it however you will with a grain of salt.

MarkL

I think the automatic is set up to shift at around 3000 rpm when cold to help warm the catalytic converter. I have a 6-spd, but I've read this.

I know what you're saying about keeping the speed down, and not to disagree, but miles per hour isn't the important thing, its rpm. I mean, you can do 25 miles per hour in 1st gear at about 6000 rpm -- not too good for a cold engine . On the other hand, 60miles per hour at 2500 rpm is cool!

On a related note, once I had a new car and the manual said keep it under 4000 rpm for the first 1000 miles. My wife drove it with me and I told her to take it easy. At the first stoplight, she pushed it pretty good and wound it out to 4500! She said, "I was just accelerating normally"!

champa

I've heard, and I am pretty sure it is in the ML's manual that you should start driving so that the car will warm up faster and thus reduce emissions and avoid excesive engine wear caused by not enough oil going up. The ML does have a code so that the transmission will hold the gears longer to keep RPMS higher so as to warm the car faster (this does not mean you should floor it with a cold engine).

my 0.02

susemu

I did notice the same on my 2.3l Coupe - I start the engine, wait about 10 seconds (we're having between -10F and 25F for several weeks now) and then I drive off. The car will shift "late", at around 2800 RPM the Auto will shift. This goes on for about 1 minute or less. After that I still go easy on the throttle (up to about 3000 RPM and once the temp gauge hits 60-80 degrees I drive "normally" (which is propably a lot more restraint then most of you guys here, well I'm in my 40s now.... :o ).

TNblkc230wz

The only reason to allow an engine to idle prior to taking off (cold or warm) is to allow oil pressure to stabilize. On a warm engine this can happen while the engine is still cranking. On a very cold engine (sub zero temperatures), it and take two or three seconds. Any longer and your engine will experience above average wear. Modern synthetic oils flow much better in sub-zero temperatures and will usually stabilize within a second. Therefore, warming a car with synthetic oil more than five seconds is a waste of time and money. I would allow a car with conventional oil to warm up about 10 seconds in subzero weather just to be on the safe side.

I would still take it easy as the rest of the rotating parts need to get proper lubrication as well. Manual transmissions, rear differentials, U-joints, wheel bearings, and parts of the automatic transmission will not lubricate until the start rotating.

Mike T.

Once the oil light goes out, the car is fair game. To drive gently, not to rev.

Rich mixtures accelerate cylinder bore and ring wear; the sooner your engine reaches operating temperature, the better for its longevity. The quickest way to warm an engine up is to drive the car.

I use very conservative warmup driving techniques: shift at 3000 rpm maximum until coolant reaches 70 degrees, then 3500 rpm maximum until coolant has been at operating temp for a couple of minutes.

The degree to which this has worked is impossible to say empirically, but it's evidently done my old 405 no harm. It has 285,000 km (177 K miles) on the original engine and it is still pretty tight, probably good for another 150,000 km minimum. Maybe it'll hit 500,000 km. Well, one hundred thousand at a time...

QQQ

I use the block heater that comes standard with my C320 so my car is ready to go once it starts.

viper

Mike T. has the best response.