Warm-up before driving ???

[jerryho]

My father insists on idling the car until the engine is warm before he starts driving. Every owner's manual I've read tells you to start driving at moderate speeds immediately after you start the engine.

What's the logic behind "driving at moderate speeds" to warm up the engine vs. letting it idle?

Thanks.

 

[Briank]

Sitting at Idle = 0 MPG

Driving gently with cold car = poor MPG

Poor is better then 0.

 

[the nsxnut]

When dinosaurs roamed the earth, and big V8s had carburetors, they all had bi-metallic chokes that really had to get warm before the engine would function properly... in the modern era, with ECUs, ambient temp sensors, and fuel injection, that is all irrelevant. The engine is performing right away... Of course, it is prudent to take it easy for a few miles until you get some heat in the oil and things expand a bit. From a performance standpoint, a 5 minute warm up does nothing but waste fuel. Now, if you want to heat the cabin before you get in the car when it's really cold, that's an issue of creature comfort. But, there is no mechanical need to do a standing warm up.

 

[4AU4LIFE]

When dinosaurs roamed the earth, and big V8s had carburetors, they all had bi-metallic chokes that really had to get warm before the engine would function properly... in the modern era, with ECUs, ambient temp sensors, and fuel injection, that is all irrelevant. The engine is performing right away... Of course, it is prudent to take it easy for a few miles until you get some heat in the oil and things expand a bit. From a performance standpoint, a 5 minute warm up does nothing but waste fuel. Now, if you want to heat the cabin before you get in the car when it's really cold, that's an issue of creature comfort. But, there is no mechanical need to do a standing warm up.

Not doubting you at all but would explain something to me then? Why do 'modern' cars run higher RPM in the morning or after sitting for a while then lower it after a few minutes?
I too have always lived by the rule of letting them run a minute or two before moving. Probably useless but I feel better doing it. :biggrin:

 

[KingsCourt]

Why do 'modern' cars run higher RPM in the morning or after sitting for a while then lower it after a few minutes? ----I'll leave that question up to NSXtasy. I think it has something to do with cold starts requiring a little more motivation at first when lubrication is at its lowest point. Then as the lube improves, less motivation (idle) is needed to keep the engine running.

I will say this: I grew up with my dad telling me to warm up the engine before you actually take off, and I did it for years. I would actually wait for the temp guage to start showing signs of life. Then one day I read in a car magazine (Road & Track or Motor Trend) that there is really no point to that. What your waiting for is for everything to be properly lubed inside the engine, and for the temp to rise to normal operating temp. The temp will reach it's optimal point faster if you have a little load on the engine (moving and accelerating), and will be fine as long as you keep the revs low during that time. If you are just sitting there, it will take longer for the engine temp to rise, and therefore actually create more "wear" on the engine during that time.

 

[Troll]

I can remember been told at the driving school NOT to let the car idle till it's on operating temperature but start straight away.

 

[the nsxnut]

Why do 'modern' cars run higher RPM in the morning or after sitting for a while then lower it after a few minutes?

Even though the motor can be safely loaded (driven) right away (as soon as oil pressure reaches normal), it is still important to get to 'operating' temp (open thermostat) as quickly as practical, as that is where the engine performs best. So, higher idle when cold starting. The cold start A/F is also much richer, and leans out as the temp increases.

Another indicator, all overhead valve motors will 'clatter' somewhat on cold starting. As soon as the clatter dies down, that let's you know that the valvetrain has gotten adequate lubrication, and you're good to go. Always moderate speed, part throttle until the water temp reaches normal.

Most modern owner's manuals state that it is not necessary to 'warm up' before driving, just take it easy for the first few miles.

 

[4AU4LIFE]

Thanks for explaining that to me. Makes sense now.

 

[cmhs75]

Does this " no worming car required" also apply to very cold days? Like if it's 7 C Celsius (about 50 F) outside, is it OK to just start the car and immediately drive off slowly?

 

[gheba_nsx]

As a general rule, I have 10 seconds idle if I drove the car in the last 24 hours and 45-60 seconds if I didn't...

 

[djskyy]

I usually let me cars idle....it seems to drive better from the getgo... :smile:

 

[willabeest]

I usually let me cars idle....it seems to drive better from the getgo... :smile:

i have to disagree with most of these posts. the EPA demanded that the car makers remove the suggestion to let cars warm up before driving from the owners manuals... to reduce smog. the car makers at first refused then i assume the guv made them an offer they could not refuse. so i let my cars warm up a good long time.
i might add - different parts of the engine warm up at different rates.
so you want everything to be nice and warm and meshing together nicely
to reduce wear on the engine.
next time you see someone driving an old car if they have more than 250K on the engine ask them if they warm it up before driving. find out for yourself by asking the ones with the proof!
of course if you are a caffeine addicted yuppie and cannot stand the thought
of someone getting to Starbuck's before you do go for it - the engine rebuilders of america salute you.

 

[Briank]

next time you see someone driving an old car if they have more than 250K on the engine ask them if they warm it up before driving. find out for yourself by asking the ones with the proof!

I had an Accord with 195K on it and it ran fine and only used a quart of oil in 4000mi. I did not warm it up before driving even when it was -22 F.

 

[willabeest]

I had an Accord with 195K on it and it ran fine and only used a quart of oil in 4000mi. I did not warm it up before driving even when it was -22 F.

i assume that is when you sold it? cause 195K is not 250K.

 

[fangtl]

What's the logic behind "driving at moderate speeds" to warm up the engine vs. letting it idle?

Thanks.

The goal is to give the oil a chance to get where it's going, into the head and valves, and frankly the oil will flow faster if you drive the car than to let it idle. Thus allowing the car to operate in "normal conditions" faster.

BTW, instead of "driving at moderate speeds," did you mean to read "drive at moderate RPMs?"

 

[NCC-1701D]

When the outside temperature is -23 C in the daytime without taking into account of windchill. I let my car warm up for 15 minutes before I even get in my car....(got to love remote car starters..It's a must have up here)

but in the summer I like to start car and wait a few seconds just to let everything get lubed before I drive away.. As long as you are not hard on car in the first few minutes I think you should be fine...

 

[Briank]

i assume that is when you sold it? cause 195K is not 250K.

After 13 years and 195K the original clutch gave up and I decided not to repair it. Donated it to Rawhide Boys Ranch.

 

[NsXMas]

I have an Accord with 211k miles on it, and I don't warm up before I drive. The car runs like new.

 

[hlweyl]

of course if you are a caffeine addicted yuppie and cannot stand the thought
of someone getting to Starbuck's before you do go for it - the engine rebuilders of america salute you.

Such venom, wow! What's wrong with caffeine anyway?
:biggrin:

 

[willabeest]

Such venom, wow! What's wrong with caffeine anyway?
:biggrin:

hehe i just gave it up for my New Years Resolution!

THe Horror oh the HORROR!