Oil changes: Warm or Cold?

[ruffdog]

From years in a service dept, I like changing the oil hot/warm so I don't have to wait as long for it to drain. Put the vehicle on the hoist/ramps, pull the drain plug, go to the parts dept to get the filter, get tools, do undercarriage inspection, install drain plug, continue.....

With any hot engine work on an aluminum engine, be careful when torquing spark-plugs and drain-plugs. The aluminum is a bit softer when hot.

 

[3Lfarms]

For what it's worth RAM on the eco-diesels now wants a half hour draining time.

FYI, you also have to wait 30 minutes after refilling the oil before starting the engine. Apparently, a few engines have grenaded because the lube places will dump the oil in and then start it right up. Something about the internal construction causes the oil pump pickup to get a bubble in that prevents it from priming quickly. Waiting let’s the oil in the pan force oil up the pickup tube so the pump can prime itself.

 

[DieselBound]

If there are particles in your oil that you're worried about then you're either running poor filters or you should crawl back under the bed covers (to hide from all the ills out in the world). FACT: oils are supposed to suspend particles; larger particles, ones that are likely to be of a concern, are going to get trapped by the filter; the rest are not deemed large enough to be a problem.

Most of my oil-changing is with my cars, and I do it top-side via a vacuum extractor: VW TDIs have easy to access cartridge filters that are replaced from the top side). Cold oil would take a LONG time to suck out. At 10k mile change intervals an extra start ain't nothing to these engines: that's like 20 extra starts in 200k miles (based on my average commute distances I'd be looking at 4k starts to cover 200k miles- 20 extra starts on top of 4k starts, pfft!).

 

[PILOON]

A simple test will decide it 4 you.
Take a quart of your favorite oil, warm 1/2 on the stove and put the other 1/2 in the freezer.
Now pour them out side by side.

Next save that oil 4 the tractor.

 

[cat fever]

Good point Piloon,

I always keep the new oil in the house (for winter changes) until ready to use just so it is warm and pours out of the container faster.

 

[RjCorazza]

For the record, engine oil thins when hotter and thickens when cooler. If the oil thickens LESS then it gets a lower (W)inter rating. There is no direct relationship between the (W)inter number and the viscosity number.
For example, a 5w40 oil is a 40 weight oil that thicken LESS in cold temperatures than a 10w40 oil. The winter spec is based upon a different test and scale and has NO relationship to the viscosity (40 in my example).

 

[Oldoak]

A simple test will decide it 4 you.
Take a quart of your favorite oil, warm 1/2 on the stove and put the other 1/2 in the freezer.
Now pour them out side by side.

Next save that oil 4 the tractor.

For the record, engine oil thins when hotter and thickens when cooler. If the oil thickens LESS then it gets a lower (W)inter rating. There is no direct relationship between the (W)inter number and the viscosity number.
For example, a 5w40 oil is a 40 weight oil that thicken LESS in cold temperatures than a 10w40 oil. The winter spec is based upon a different test and scale and has NO relationship to the viscosity (40 in my example).

In a very simplified example, I believe PILOON's comment would support that.

 

[nikerret]

I NEVER change the oil in any of my vehicles unless the engine has been run for a good long while and everything is hot. I want all the crap that may have settled out of the oil thoroughly suspended in the hot oil and drained out of the engine.

Totally agree...... Not cold, not warm, HOT! Otherwise, you're leaving more stuff behind.

These^

I won't start the tractor to change the oil, I will change the oil after the next time I need to use the tractor.

 

[THEPARTYHOUND]

Always change the oil hot so that the metal particulate is suspended in the oil. It is a common misconception that oil filters will filter out metal particles, but in fact much of this abrasive material is much smaller than the filter can clear out. Don't believe me? Stick some powerful magnets to your oil filter and leave them there for the duration of your change interval. When it gets changed again, cut the filter open and compare the amount of metal particulate with another used filter without the magnets! You'll be amazed by the amount of shavings floating around freely inside our engines and passing through a filter!

 

[Wood_Butcher_Dav]

OK let's continue.

If hot oil causes metal particulate to be suspended in the oil, where is this particulate when the oil has settled, on bottom by drain plug? Floating on top of oil pool in pan that will get drained when the plug is pulled? There are many more non-metallic components that are inside an engine that a magnet will not affect.
Two quarts of oil, one always at 50 and the other at 140 degrees. Drain them, how much would be left after waiting a certain time? Sure in a minute there would be a difference but what about 10 hours.

Cold or Hot just depends on how much time you have to drain the oil.

Slow day today

Dave