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I was reading about the purpose of engine assembly grease and apparently it's purpose is to provide the initial lubrication when first starting up the engine until the crankcase oil has time to coat everything.

But how is this any different from starting up a car engine that has been in storage long enough for all the oil to run off the parts? If you need to have a disassembled engine to coat everything inside with assembly grease how come I never hear anything about needing to disassemble a stored engine to lubricate it before starting it up?

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    $\begingroup$ Why would the oil all run off unless you rinsed it with solvent ? Long ago ( like all my comments) I pulled cam shafts from Olds V8 engines in a junkyard. I needed a cam to send for modified regrind . I pulled a few because I had to pull a few before I found one with no worn lobes. All the cams had a film of oil. $\endgroup$
    – blacksmith37
    Feb 28 at 18:53
  • $\begingroup$ @blacksmith37 If that's the case then that's the reason. You just hear people say that a car in storage for a long time has all sorts of potential maintenance issues and one of the ones is that the oil runs back to the sump. $\endgroup$
    – DKNguyen
    Feb 28 at 20:32
  • $\begingroup$ @DKNguyen oil does run back into the sump - how else do you get to change it? $\endgroup$
    – Solar Mike
    Feb 28 at 22:29
  • $\begingroup$ @SolarMike Off the rest of the engine into the sump so you have a dry start if it hasn't been run for too long. Is the intent my of question not getting through? $\endgroup$
    – DKNguyen
    Feb 28 at 22:34
  • $\begingroup$ @DKNguyen you wrote that oil running back into the sump is an issue - I was pointing out an advantage. $\endgroup$
    – Solar Mike
    Mar 1 at 6:43

2 Answers 2

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If I have to start an engine that has been sitting for a long period, then I will remove spark or heater plugs or similar to remove compression and spin the engine over on the starter so the oil pump circulates the oil.

If one takes off the oil cap, it can often be seen when oil has reached the valve gear.

After that, fresh fuel, refit plugs and start then let it idle comfortably. Do remember to check coolant and belts etc.

However, one trick some do when building new engines is to either fill the oil pump lobe spaces with a light grease to get the pump to pick up oil quicker on initial start. Or another method is to "back-fill" the oil galleries by pumping oil into them again prior to the first start.

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  • $\begingroup$ I guess what I'm asking how does that even compare against the initial greasing that the engine gets when disassembled? It feels like that wouldn't be enough because couldn't you just do assemble a new engine first and then do the process you described? $\endgroup$
    – DKNguyen
    Feb 28 at 18:29
  • $\begingroup$ @DKNguyen when I built my v8’s I used graphite grease on all bearing surfaces during assembly then built the oil pressure up as described anyway. If you want a comparison, build two engines based on the two methods and test - but not sure if you will have comparable or reliable results. Especially when considering servicing intervals and choice of oil quality. I worked at a hydraulics place and motor oil fresh out of the can was rated at 7/10… $\endgroup$
    – Solar Mike
    Feb 28 at 18:42
  • $\begingroup$ I didn't mean a technical comparison of performance. I meant how come one less extreme method seems to be required in one case but is not sufficient in the other when when they both appear to be very similar scenarios? $\endgroup$
    – DKNguyen
    Feb 28 at 20:33
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The viscosity of grease is much greater than that of engine oil. That means that it will be very difficult to run off.

Some related reading is about the pitch-drop experiment in Queensland. It's a experiment that started in 1927 in Queensland.

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It measures the time between bitumen drops (which are in the order of a decade). Bitumen has a viscocity in the order of million.

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