oil change - dry starts

[dlb]

i did an oil change yesterday and afterward, i remembered my buddy chastising me once for doing a 'dry start' afterwards. that is, he said i should disconnect the power to the dizzy and crank the engine for a little while (i don't know how long) but, having never seen the inside of a block, i'm not sure what this achieves so here i am, asking you guys.

is the idea that during an oil change, all the oil that is up in the oil pickup tube is also drained out? that makes sense to me because it would then take a few seconds for the pickup tube to suck more oil up and spit it out wherever it needs go (presumable over the crankshaft?). or does oil drain out of the pickup tube after the engine has sat for a while anyway? if that's the case, it seems like the dry start wouldn't really matter since your engine would theoretically be under the same conditions any time it is started after sitting for a few days.

if anyone wants to illuminate the facts on this i would appreciate it. i've always done dry starts after oil changes and never had a problem but don't want to push my luck.

[arbskynxnex]

For our application it sounds like a folk remedy to cure an imaginary problem in my opinion. Oil isn't water, it is viscous and will hold to parts for a while. Even if all the oil magically came off of all the parts in the engine and you disconnected the dizzy, you'd still be cranking the engine with dry bearings, etc and causing the same amount of wear as if you'd started it.

If your critical engine parts were unlubed after an oil change, you would have to strip the engine apart and apply some sort of moly-lube to everything just as you are supposed to do when you rebuild an engine and start it for the first time, since in that case there IS no oil on anything.

[toughtercel]

On top of the Cylinder head ,that where we adjust the valves . well there are about 3 or 4 pool of oil that always sit there, that over a cup of oil , I had a car with very dirty oil so I change it once every 3,000 km for a year till it cleaner but it didn't help to clean the ports or oil gallery. It will get smaller and smaller ports .

[danzo]

A 'dry start' is a bit of a misnomer as arb points out. The reason for preventing the motor from running while turning it over after an oil change is to prevent the bearings (mainly the mains) from being pounded by the connecting rods (as the cylinders fire) while the engine is getting no/little oil pressure. Sometimes you can hear more clatter before the engine's oil system 'primes up'. But this wear happens for only a few seconds, the amount of actual wear on the bearings is extremely minimal in the long run.

You're OK to not disengage your ignition, I've never done it any of my cars for the above reasons with no ill effects. You should grow back your formerly awesome hair.

[Petros]

Okay, here is the definitive answer: oil does drain out of the engine, the bearings and galleys each time you stop the engine. The longer it sits without running, the more slowly drains out, and the thicker the oil becomes as the lighter parts evaporate out (after many years without running motor oil in the engine becomes like tar). IT will also have a dry oil filter after a change, and take a few seconds longer of running before pressure builds up. But as arbskynxnex points out, there will be a coating of oil on everything, and the main bearings also have deep grooves in them specifically for holding oil for start up. But the rod bearings, that actually have more stress on them, do not. Many engine studies have shown that 90 percent of the bearing wear over the life of an engine comes from the cold start ups. So presumably the bearings will last up to 10 times longer if you pressurize the oil galleys before each start up. After an oil change it takes a bit longer to pressurize than on a normal start, and that means more wear.

Here is really the issue however, if you change your oil and never allow the level to get low (so the engine never runs without oil pressure), it is not the bearings that cause you to have to rebuild the engine after many many miles. The seals get brittle and start leaking, the valve seats and faces get beat up (and sometimes exhaust valve stems fail and trash the engine), rings wear out, head gaskets can sometimes fatigue and give up (even if never overheated), piston skirts fail and trash the cylinder. However for the head related issues, it can be removed and valves and seals replaced/rebuilt for far less than rebuilding the engine, but clean oil will not make the valve seats last longer.

The rings in my experience are the big wear issue, they too ride on a layer of oil. If that oil is not clean it wears both the rings and cylinder bores. IF oil takes longer to splash on the cylinder walls, the rings scrap it off than it glazes and wears the walls (the rings are lubricated by oil spraying off the connecting rod journals onto the cylinder walls as the crank spins around). Also, drawing in less than perfectly clean air will also deposit dust and grit on the cylinder walls as it runs, with predictable results. So good performing air filters are essential for long engine life. Vac leaks by the way, also let in unfiltered air, not good for engine life at all. I have also seen piston skirts fatigue and break off, sometimes trashing the cylinder bore, the most likely cause of this is a worn cylinder bore that allows piston slap, and this comes from dirty oil, or unfiltered air intake.

So, yes the no oil pressure start ups can be an issue, but it is only one of many issues that determine engine life. It is an extra step to crank the engine before a start up that might ad to bearing life, if nothing else ever goes wrong with the engine.

Also, to add more confusion to the issue, when I worked for the Nissan racing team, before EVERY cold engine start, we would slip the cog belt off the dry sump oil pump (it uses an external oil pump, looks like a small air conditioner compressor), and turn the oil pump by hand until we had oil pressure (basically prime the whole lubrication system). Than slip the belt back on and start the engine.

Because of this I will ALWAYS crank over a new/rebuilt or freshly assembled engine or installed head with the distributor disconnected until I see the oil pressure light go off (or now with a pressure gauge when the needle comes off of zero). I always use assembly lube, especially on the cam and rockers, and bearings. I also soak the rings, valve train and valve stems and cylinder walls with clean motor oil before assembly as well. But cranking for about 30 seconds or more, and than connecting the distributor, I always do when the engine was not run since it was apart. Doing this would be a good idea if you get a car that has not been running for a number of years, I would also put some light oil or AFT into the all the cylinders through the spark plug holes before I crank it too.

I do not do it after a routine oil change, because I just had the engine running before I changed the oil and all the galleys should be full and have fresh oil in all the bearings. It might help the bearings a bit to do it with every oil filter change, but not likely to be very much worse than a normal cold start.

I have always thought it might be an interesting way to lengthen the life of an engine to have an auxiliary electric oil pump that comes on as soon as the ignition key is turned, and there will be no power to the spark plugs until oil pressure is achieved. It prevents dry starts, and prevents starting at all if the oil is too low. It would also act as a n auxiliary oil pump if the mechanical oil pump ever failed. But this added complexity would is not really the issue that causes engines to be replaced. However I do not like added complexity, and running dry of oil (because of leaks or worn rings/seals), overheats, worn out rings and valves are usually what triggers a rebuild anyway.

IF you care for your engine, you many never notice a difference in the bearing wear before the rest of the car corrodes away and turns back into the elements of the earth anyway. So I only do it on a start after the engine was apart and put back together, be it a full rebuild or not.

No harm done if you do it with each oil/filter change, but you may never notice a difference anyway.

[splatterdog]

While this wouldn't help with oil change starts, it would on every other "dry start". http://www.stockcarracing.com/techartic ... index.html It acts as a reserve oil pressure source for racing type conditions. When a shutoff valve is used, pressure can be contained just before shutdown and released just before start up. Just like priming a new engine.

As long as you aren't on high idle, I wouldn't sweat it.

If you are quick with the spin on filter you can fill it up prior to installation, thus reducing prime time.

[Petros]

If you are quick with the spin on filter you can fill it up prior to installation...reducing prime time.

Now that you mention it, I forgot to say we also did this to the race car (it used two large remote mount filters). So I also make a habit of filling my small Tercel filter when I change it. The oil does not really spill out much because of the nature of the design. You have to fill it slowly to allow the element to fully wet out with fresh oil.

By filling the filter, rather than cranking, you likely reduce the prime time to about the same as any cold start. And do less wear and tear on the starter and other moving parts.

Good call Splatt

[dlb]

well hot dog, who knew such a simple question would garner such verbose responses! it's one of those questions that you feel dumb asking initially, but are glad you did afterward. thanks for all the info!

fortunately, i have always filled the filter prior to installation. i put a rag beneath the old filter when i take it off to catch the spill so i just leave it there for when i put the new one. that catches the fresh oil spill while i thread the new filter on.

danzo, i should post the pics of my orange and black dreadlocks sometime.

[danzo]

danzo, i should post the pics of my orange and black dreadlocks sometime.

Part of some kind of Halloween costume? Maybe I'll dig up some of my 'hair pics' too. Hey this may be the idea for a cool new thread - 'ridiculous member headshots'.

[dlb]

https://tercel4wd.com/forums/viewtopic.php?f=9&t=7227

[Nytroz]

I only do this (spining with spark plugs out to let the oil get everywhere) when the engine was disassembled and cleaned (like overhaul etc) and there is no oil in oil pump and bearings etc. IMO not needed during regular oil change.

There we similar topic on local Celica forum, some guy bought "oil pressure capacitor" on e-bay for his rare GT4 WRC Celica. Looks like presurized tank for oil with electromagnetic valve, it accumulates oil under pressure and locks it, releasing it back to the oil line on next "ignition on" event

[Lil Beast]

Also, to add more confusion to the issue, when I worked for the Nissan racing team, before EVERY cold engine start, we would slip the cog belt off the dry sump oil pump (it uses an external oil pump, looks like a small air conditioner compressor), and turn the oil pump by hand until we had oil pressure (basically prime the whole lubrication system). Than slip the belt back on and start the engine.

Was wondering instead of priming by hand, if the would be a way to tap a compressed air inlet that would pressurize the external oil tank and add like a ball valve to a line that goes out the pan and back in the pump. Adding some kind of catch tank to it, so maybe that way could send the oil thru engine by opening ball valve, wait for oil to come out, close it back and poor the oil back in tank? Could get a reading of ur oil as well everytime! Does it make sense?

Kind of inquiring, might gonna have to use dry sump, as I heard rumors about the oil pressure going way down at high revs on 4ag.