In high school autoshop we tried to blow up a Honda sedan, one of the first ones into the country. It was one of those little boxy cars that looked like an Austin Mini Cooper. It had a motorcycle engine in it, 600cc IIRC. We fired it up and bricked the gas pedal. It floated the valves and peaked out with a horrendous amount of noise. After about 3 minutes of this we realized it could be a long wait and unbricked it. Pretty quickly it was decided we could drain the oil and shorten things up quickly. We shut it off drained the oil and started it again. Re-bricked, it ran for about 15 minutes valves floating until it actually ran out of gas. Told by out teacher "you can have only this gas", about a gallon, we decided to up the anti and drained the coolant too.
No oil, no coolant, we tried a third time. This time about 10 shocking minutes into the run something caught fire. The engine continued unabated but the a fire was not going to be allowed by our teacher and we had to shut it down and extinguish the fire before things went completely sideways.
End result.. an engine can potentially run a very long time with no oil. It was felt that the engine being pretty old was a big help in the process of not breaking and that a new 'tight' engine probably wouldn't last long, but that was one test we couldn't afford.
most experiments i have seen were with quite worn down engines at no load. quite a few of them did run for quite some time. if they were stopped before they seized up, and later on filled with oil and coolant however, they were quite a bit more rattling then before the experiment, so running without oil and coolant had taken its toll....
i guess the amount of load is the important factor: if there is hardly any load temperatures will not rise very fast, so the conditions that would make seizing up likely may not be reached any time soon. in your car the coolant temperature rises quite fast after the start to about the optimal temperature, but under normal driving conditions it may well take about 20 minutes before the oil temperature stabilises. thus, a temperature rise within a journal bearing may take quite some time given sufficient play and low load.
I've been a member of several car clubs where running a junk engine with no oil and betting on the time until catastrophic failure was an annual fundraiser. Its often 5-15 minutes.
Not to sidetrack, but engine oil pressure is irrelevant vs flow. Many racing engines for example run at zero pressure but with a large volume of flow, generating pressure being unnecessary work. OTOH generating steady pressure is a great indicator of flow, and I'm among those who hate the newer vehicles being sold without an oil pressure gauge having owned many classics and clunkers with questionable flow.
Well, here's my personal experience:
Many years ago when I was a youngster, I borrowed my brother's VW Scirraco. I was driving in city traffic when the water temp light came on. I figured I'd limp to the next gas station and check it out. About a block later the engine seized. Turned out it was the oil pressure light, not water temp. The "while you wait" oil change place had stripped the drain plug and stuck a rubber plug in instead. It fell out, stupid youngster didn't recognized the little picture on the warning light and the engine promptly froze. Big brother was not happy!
Back in about 1970 in the UK, it was late one Sunday night out in the country after the pubs had closed and I was about 10 miles from home and motoring briskly to get there when I heard a slight noise that I did not recognize. Looking down at the instruments, I was just in time to see the oil pressure needle drop back to zero. Looking in the rear view mirror I was able to see in the headlights behind me a great cloud of smoke. When I pulled over to check under the bonnet/hood of my Jowett Javelin, I found that the flexible oil hose to the oil cooler had split so that the whole contents of the sump had been pumped onto the road.
What to do? Well, I needed to get home and had no way to call a tow truck anyway, so I just got back in and motored somewhat less briskly the 10 miles home. The engine made it back without incident, and the next morning I put on a new hose, refilled the sump, and drove the 30 miles up to London to work. The engine survived that incident without apparent damage, and I attribute that to the aluminium crankcase which may have dissipated the bearing heat reasonably well, and the fact that the engine was moderately high mileage so not "tight". I assume that this would not have been possible, and I would have been dead in the water if the engine had hydraulic lifters.
I've read all kinds of stories about oil loss and how long the engines ran even under load. One guy claimed I think it was 90 miles of driving with out oil. And other cases as well as personal experience with engines seizing from lack of oil and running for unknown time with out it, and then adding some oil and push starting to break the crank free, and doing this all multiple times, with no known ill effects from it. So just because it seizes does not mean that is the end of the bearings or other parts. Hydraulic tappets? No big deal they can go a long time with out leak down. Just letting the average engine sit for a month or more no banging and clattering from tappet leak down at start up.
In the world of 2-stroke dirt bikes, if the engine seizes and then frees up later you took out the top end. If it seizes and stays seized you lost the crankshaft.
The problems I have seen in oil less 2 stroke gas engines is mostly scored piston skirts and cylinders, most small ones run in frictionless bearings and they seem to last for quite awhile with no lubrication, even longer if there was no fuel air in the crankcase washing them dry.
My brother ran my Zundapp 2-stroke dirt bike out of gas on the trails and got some from someone riding a 4 stroke. It seized in short order. I replaced the piston, rings and wrist pin, started it up and heard the most horrible knocking, shut it down and went to bed. The next day he got home from school earlier than I did and rode my bike again, supposedly not noticing the knocking. I nearly killed him when I got home but tore the engine down again instead. This time it was evident that the big end bearing needles were breaking up and getting between the head and piston. Ouch! So now I needed a new head, piston, rod & bearings. Took me months to get the parts from Germany. Eventually I got it running again but that bike became a parts bike for a newer one.
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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
Not from what these folks are saying about the 2 strokes they've dealt with. I've seen and experienced cases where the plain bearings have run for a long time with out lube.
There is a reason most 4-stroke dirt bikes run ball bearing main and roller bearing rod bearings. They're heavier and have a shorter life expectancy than a journal bearing which are negatives but they can handle oil starvation better during some of the extreme lean and pitch angles seen while riding off-road and during the moments of zero gravity while the bike is airborne.
I've seen may TV infomercials, where an engine is filled with snake oil, then emptied and run dry. The ability for it to run dry is credited to the snake oil. It's impressive if you are expecting (like most people) it to fail in seconds.
Some of the so called snake oil has real good EP qualities, I'm not real sure how EP lubes work with or helps soft bearing materials? Though in areas where a strong EP lube is needed it works great.
