Warm up or not?

You smell like poo.



Seriously though.

 

Only because it is burning more fuel but that can be easily offset by cold air flow.
I had Tdi that burned almost no fuel, so idle would not warm up the car even if you left it for a month idling. Needed to start driving with frozen windows which was major pita.
Once on the highway keeping RPMS above 2k it was ok but if you dropped on neutral and started rolling down the hill engine temp would started dropping so quickly that by the bottom of 2 mile hill car needed to warm up again. Solution was to cover the front grill to reduce airflow
I hated that car for that one time all my doors and windows froze it shut. Could not get into the car for almost a month.

 

i have heard it both ways. I personally let mine warm up for a bit before i get going.

 

I will throw a few facts and corrections on the table just to help everyone keep calm and carry on. First of all, modern engines DO still drain down. In fact, they are getting worse. I work in the timing drive industry and we spend a lot of time studying how long it takes for oil to get to the hydraulic tensioners and other components within the system. Oil drain down depends a lot on how the engine oil galley is designed. The old way of doing things was to feed the engine from the bottom up. Oil would flow from the pump in the pan directly to a low mounted filter then directly to the main bearings up through the block and into the heads. This design takes a VERY long time to drain because most gerotor pumps will not drain back. The trend now is to put oil filters up high on engines (like Toyota has done for years). This means oil comes from the pump high on top of the engine to the filter then it feeds down to usually a rifle in the block which then branches both up to the heads and down to the mains. With no filter or pump to prevent drain back, these engine completely drain down in 5 minutes or less with an exception of a thin oil film remaining. Every time the engine is fired, it basically has to refill itself all over again. We have measured times as high as 30 seconds on cold starts. Keep in mind, the last thing to get oil in these schemes in the main bearings. Now to Chris’s point about the oil pressure light. Most sending units are located close to the pumps which mean they register acceptable pressure before the engine has actually fully pressurized.

Now as far as oil viscosity. The comment regarding even modern oils being like molasses isn’t actually that far off. Oil viscosity is usually rated at two reference temps, 40C (104F) and 100C (212F). Viscosity curves over a temp range are highly non-linear. They are usually looked at on a log scale. With this in mind, even a 5w-30 viscosity gets very high very quickly as temperature drops. At 0C (32F) 5w-30 has a kinematic viscosity is 541cSt. At -20C (-4F) kinematic viscosity is 2839cSt. The kinematic viscosity of molasses at 100F is anywhere between 281-5070cSt depending on it purity. So essentially, 5w-30 at most winter starting temps (at least in the north east) is equivalent to molasses on a hot day. Viscosity doesn’t change because an oil is conventional or synthetic old or modern. Viscosity is constant across all commonly rated oils.

It’s not just about oil either. It has to do with combustion quality. Fast idle is there to keep your engine running in place of a choke, not to warm the engine. Getting in and going full throttle when cold leaves a lot of unburned fuel to create deposits.

With this said, based on the data I have and what I have seen on dyno tests, I would recommend waiting at least 30 seconds to a minute before you throw any car in gear and drive off. Further, I would recommend keeping the rpms low until the engine has had time to warm (at least until the needle starts to move on the temp guage). This is also recommended by car manufacturers. You can drive with a cold engine, just don’t drive it hard. It recommends this in the Tacoma manual. BMW actually has a meter on the tach on some of the higher models that indicates safe operating rpm until the car is warm. This is a reasonable practice that will avoid any potential issues far down the road.

 

P.S. Anything Diesel is a completely different story.....

 

I have always found 20-30 seconds is enough for idles to drop. I drive it right away I just don't rev it high off starts. I think the idle engine for 5 minutes is old habits from back in days when a 3,000 mile oil change was needed. If it's cold enough to need that much warm up then you probably should be using an engine heater anyway. Everyone will do their own thing no matter what is "better for the engine" whatever that may be.

Edit: the above(both of them) seems pretty good to me.

 

Right. I got 4 generations of mechanics backing me up on this. What do you have? French canadian word of mouth? Get a clue.

 

I haven't read 134 posts .... I start it, settle in, put on my seat belt, turn on the radio ..... then I take off.

Now, my wife in her Accord ..... nah, I don't even want to get going on that!

 

Even the engineers i know from actual car manufacturers that agree that new engines don't need as much warm up as before still say 1 or 2 minutes depending on how cold it is is still recommended.

 

I jump in and drive, unless its cold a shit outside then I sit in my house while the heater is on other than that. Turn it on and go 50K never had a problem yet on my taco. Have had 2 other vehicles over 150k did the same thing with.

 

One of the more insightful posts on this thread, thank you for the info dalsmthme!

 

And another...

 

Some interesting thoughts on this subject but I think I will still do my normal warm up in the mornings just seems like it goes into reverse smoother and runs better...thanks

 

One item to add for those that idle long time. At idle (around 700RPMS or so) oil pressure is probably around 1/4 of what should be. In theory thats enough to lubricate but there are always flat spots. Especially if truck is parked at angles. So from time to time hitting 2000 RPMS is good thing to do .At 2K RPMS pressure should be maxed
For easy cold starts parking truck nose down will help draw oil to pump (pump is located next to crankshaft on the front). Having oil level at top mark will not hurt too. None of these things will make super big difference but they all add up on the end.

 

I feel the truck exist to serve you and you don't exist to serve the truck. If it wears out a little bit more because of an improper warm up then so be it. I bought it to haul me and my stuff around comfortably and when the weather is 20 below I want it warm before I get in it.

 

I am not sure why everyone is so worried about idling. It's not going to hurt a thing other than MPG's. The 4.0L makes plenty of oil pressure at idle and there is no pick-up issues in the pan. OEM's idle engines for 100's of thousands of hours. Not a problem....

 

Seeing that you had to resort to calling me a name tells me you know you fucked up. Consider yourself owned OK so everyone out there who krazie said was "flawed" or a "knave" and a "tool" for giving your trucks an idle warmup-you can rest easy because "the man" himself krazie does it too AND...he uses a block heater also. So he himself is not really buying the bullshit he preaches here-he too likes to "get things circulating" before he drives off. By the way I tried firing it up and driving off right away-don't like its effect one bit and I will go back to my way.

 

i like to start it up and let it idle to 1 min before i go. its a habit for me.

 

Yeah no, but whatever helps you sleep at night. Me prepping the truck for travel doesn't equate to letting it warm up. I use a block heater because that's not letting the engine produce condensation in the oil.

I resorted to name calling because the mass of information supporting my claim is overwhelming. Consider it the verbal equivalent of using a hammer to pound a nail in a wall.