The Theory of WARMING UP the engine upon startup.

[DOCTORBILL]

This thread is a continuation of a conversation that was in FEESIAGIRL's
"Roaring Noise When Driving - Can't figure it out???.

We were discussing repairing the Metro's 5 speed manual transmission.

The shop repair manual can be found at
http://www.teamswift.net/viewtopic.php?p=145642

Hugemoth made this statement regarding a cold transmission -
"Best thing for the car is to start up and drive off slowly rather than let it warm up,
even in very cold weather."

This was in regard to the transmission oil "splashing" up onto the bearings and
gears inside the transmission upon startup after setting overnight (cold).

Hugemoth thinks "The oil isn't really "splashing" around in there, instead it's more
like one of those things that is made to dip in honey and drizzle it on to toast.
The viscosity of the oil causes it to be drawn up by the ring gear. My bet
would be that thicker gear oil would do a better job at sticking around on the
bearings than thinner oil."

So - it might be better to slowly get moving to have the moving transmission
gears 'slop' the oil around to get everything all lubricated.

I can buy that - but - isn't that just the opposite for the engine itself?

I understand that almost all engine wear occurs in those few seconds that the
pistons are travelling up and down inside the cylinder walls w/o any oil lubing
the friction - until oil is forced up there by the moving pistons.

Same for the bearings - best to put minimum load on them until the oil has
had a chance to get to the bearings.

Then again - someone who's opinion I respect said that there is no point warming
an engine up past 30 seconds, because by then the oil has arrived at the
bearings and rings. Any more "warming up" is a waste of time and gasoline.

Any studied opinions on these "theories" folks.

After all, they are all "Theories" - I doubt that any scientifically run
experiments have been done with negative controls to prove any of this.

On a personal note - I believe or have faith in warming up an engine just to
let it reach equilibrium if nothing else.

Allow everything to warm up and lube up before stressing the moving parts
and load bearing bearings.

I can't prove it, but it "seems like a good idea!"

Normally I abhor that last phrase since many really bad things have been done
using that phrase...

So what is best in this life (Conan's Captors talking around the campfire) ?

In winter, what is best - a five minute warmup idle or a few seconds followed by
a slow driving away...?

Both sound appealing. Will the compromisers say - RIGHT! Two and a Half Minutes warmup old chap!

DoctorBill

[Hugemoth]

When you start a cold car, oil is delivered to the bearings and pistons within the first second. There's no point in waiting to drive off, but start out slowly.


From Tom and Ray, the Cartalk guys on Public Radio...

Dear Tom and Ray:

I know we aren't supposed to let our vehicles sit outside on frigid mornings, motor on, idling to "warm up" while we quaff another cup of Earl Grey. I've heard you mention that before. What I can't remember is why. When I quoted this rule to a co-worker, she sniffed "But that's counterintuitive." Can you tell me why it's bad? -- Cathy

Tom: Well, these days it's only bad because it's wasteful.

Ray: It used to be bad for the car. Twenty years ago, when most cars had carburetors, fuel would pour into the cylinders on a cold start. And left to run in cold-start mode for 15 or 20 minutes, all that excess gasoline would dilute the oil, which will shorten the life of your engine -- not to mention your catalytic converter.

Tom: Fortunately, all newer cars are fuel-injected now, and fuel delivery is monitored by computer. So gasoline will no longer just pour into the cylinders, because the computer determines the precise amount of fuel to send in through the injectors. So, you will not do any harm to your car these days by warming it up -- even for a long time.

Ray: It is, however, still completely unnecessary to let your car sit and warm up. Engines warm up fastest when they're driven. So, as long as the engine starts and keeps running when you put it in gear, you're good to go. Just drive it gently for the first few minutes (don't jump right on the highway and go 65), and you'll warm it up quickly and efficiently.

Tom: By letting it run, you're just wasting gasoline and polluting the neighborhood.

Ray: But, you might ask, isn't it worth a little pollution and wasted natural resources so my feet can be toasty the moment I get in my car? Well, that's a personal, ethical decision that each one of us has to make by ourselves -- like whether to leave the water running while we brush our teeth.

[DOCTORBILL]

"When you start a cold car, oil is delivered to the bearings and pistons within the first second."

I can see that in Kaahleefooornyaah or even in the South, but would it be true
for Washington State on the East side or in Montana where in winter we can get
down to 10 °F (-12 °C for the Canadians).

What does it get down to in Canada or Northern Alaska, maybe near Anchorage?

Wouldn't it be better to wait 5 seconds in that case before driving away...?

That 80W-90 Gear Oil must be like Orange Sherbet inside the transmission at 10 °F...

Just being a butt.

DoctorBill

[Woodie83]

Hi there, been lurking for about a month, finally felt compelled to join up and mouth off. Everything up until now will be known as "the good old days". :-)

Your engine has full oil supply as soon as the light goes off, two seconds max, thin oil flows faster. 30 seconds of idling in extreme cold makes sense, any more than that is a waste.

In the gearbox, the bearings are not a concern, the notoriously weak synchronizers are, and thick gear lube makes it worse. You want 75W-90 GL-4 only, the recommended stuff is GM Synchromesh 12346190, 2.5 quarts. You don't change it often, go ahead and pay the premium to insure you have the right lube, or learn to double clutch because it's not going to want to go into first or second unless you're stopped.

[Crvett69]

warm engines wear less and not just on start up. if you have even taken apart a engine and checked the engine bores the outside cylinders always have more wear than the middle cylinders because they run a little cooler. its especially easy to notice on V8 engines. as far as gear oil i use 85w90 in all the metro transmissions i work on and so far none have failed and they still shift the same. as far as rebuilding them its about $150 for the kit on e-bay. if you want a used JDM one with a warrenty i can probably get you one for about that price