Has anyone else here ever seen a severely neglected engine fail after an oil change?

I have seen this happen on several small air-cooled mower engines and such and one car engine.

Here is what happens. I am given a non-running mower or find one out at the curb on trash day. I pick it up and realize that the problem is something simple like needing a new spark plug or the carb has been gummed up with varnish from sitting over the winter without stabilizer.

Of course I change the oil if I can get one of these running. A few have had oil that resembles black ketchup rather than oil. I have had to try and get this out of the drain hole with a screwdriver, then top off with fresh oil to do another rinse. I then usually run another rinse of good oil and hopefully it will come out clean by then.

The odd thing is that usually the engine will seem to run fine on the sludgy oil without smoke and such. As soon as I put good new oil in the engine, things start to go bad. Massive oil burning and smoke that gets worse the more I change the oil is not unusual. Then, the rod often comes through the block. While these engines were neglected and not going to last, it seems that putting fresh oil in them hastens their demise. Has anyone else seen this and what is the explanation? I figure the bearings and such are so worn from neglect that the thick goo cushions them. I also figure that the oil is too thick to be pushed past the rings.

I know people who run mowers for years by just adding oil as needed. They never change it. While I would never do this, it seems like it works for a lot of people and that changing oil in one like this may actually not be the best idea.

In 25 years of owning lawnmowers (not the riding kind) I have never changed oil in any of them. Mower, edger, pressure washer, whatever, I don’t think I’ve ever changed the oil in any gasoline powered device I own. Can’t really explain why. I’m a mechanic (a pretty good one I like to think), you’d think I’d know better.

Yeah, I wouldn’t suggest changing the oil in them now based on my experiences. I always change the oil before it is even totally black on the stick. I figure this is really important, especially since most don’t have a filter or pressure lubrication. All the dirt and wear metals are just free to splash around inside the engine, causing more wear. I also use synthetics as they hold up better to the rigors of high temp air-cooled engines. Sure, this is overkill and I have actually transferred perfectly running engines to other frames/decks when the equipment rusts or falls apart from normal wear and tear and age.

Interesting. No, I’ve never experienced that. I do have a tendency to pick up old lawn mowers neighbors are throwing away and see if I get them running again. With Sears Craftsmen, it is usually just that there’s a very small hole in the carb bowl tube that is clogged. A crescent wrench, a can of Berrymans, and ten minutes to fix it. But I’m wondering when an engine is really sludged up, then the oil is changed, gobs of sludge get dislodged from the cleaning effect of the new oil, and one of these eventually ends up in a problematic place, which causes the crank to get jammed. I wonder if there is some kind of oil-alternative that would clean out all the old gunk, then you could refill with regular oil.

Just a thought…I’ve seen countless severely neglected engines fail BEFORE the next oil change.

I sometimes only let these neglected engines run for like 5 minutes with fresh oil to flush the old out. Sure, I may not get all the crap but I can tell a good amount comes out by the condition of the 5 minutes run oil when it is drained. It also seems like the ones that blow tend to smoke a lot too.

Yes, I have definitely seen engines with a hole in the side that failed before the next oil change. The oil was never changed and nothing was added so it just went kaboom!

It is almost like they are psychic, I will give my heart and soul for you, in spite of your lack of care for me, but now that I have care I will make you pay for past neglect!

Maybe because these little engines are splash-lubricated instead of having a pressurized oil system, they live with the thick goo better. Maybe it just sticks to everything and hides all kinds of wear, then when you put in nice clean, thin oil, things go to hell. Like putting 5w-20 in your differential instead of 80-90.

Speaking of differentials, if I can, I was going to change my fluid, put it off till spring, 03 trailblazer, dealer was $20 a quart, 2 quarts needed, auto parts store was $12 a quart, but needed an extra $10 for special stuff to add. If you are doing a rear differential, pay close attention!

A few months ago, a relative was due for a smog, but the check engine light had been on for some time. I resolved the issue, and got all the monitors to run to completion. So, he was ready to take it to the smog station.

I asked him if he was due for an oil change, as I don’t see the guy that often. He said yes. When I drained the oil, almost nothing came out, and it was completely black. Then I noticed the oil filter looked familiar, because it looked like the napa filter that I’d installed about 20,000 miles ago.

There was more oil in the filter than in the crankcase! I phoned the guy and confirmed that no oil change had been done since the last time I worked on the truck. I told him everything seemed fine, and that he was extremely lucky the engine didn’t seize up or throw a rod out the side of the block. I told him he really needs to get the oil changed regularly, even if it’s at jiffy lube, or some such place. Better than nothing . . .

He phoned a few days later and told me the truck was running better than it had in a long time, and that it’d passed the smog with flying colors.

That was a few months ago, by now. I haven’t heard anything about the truck, so I assume all is still well.

My only thought about poorly maintained mowers and the like is, if changing the oil causes their early demise, they aren’t something you can depend upon. I don’t have a flat lawn to say the least. I avoid junkers like the plague. When I was a stud, years ago, I still only lasted one year without a self propelled. Now that I’m an olderfarder, having an unreliable lawn mower and having to drag it somewhere and discard it is not an option. I know all you guys out there are younger, better shape and generally like to live life on the edge. I can " see my destiny" using crappy, poorly maintained lawn mowers and power equipment. I would use up all my money I tried to save using Junkers in therapy. ;=()

@dagosa–I am with you about unreliable lawn mowers and equipment. I’ve maintained the engines on my push rotary mowers. One mower is 26 years old and runs great. My other mower is 22 years old and it is the one I use most often. I did install a new short block on this mower some 10 years ago. I have a 2 stroke rototiller that really gave me fits even though I maintain it well. I finally found that non-ethanol premixed fuel made it start much more easily. I have a relatively flat lawn, so I have stayed away from the complexity of a self propelled mower.

I look back in envy the days when I could just mow a lawn with a push mower with a simple motor that only had to turn a blade. But for me where I live now, it’s like asking for a car with a motor whose only job is to generate electricity for the stereo. I hope law makers get together and figure out something that makes sense in making gasoline storage as dependable as it used to be. Am waiting, waiting…

I make a small amount of money finding derelict mowers and fixing them up. Generally the first thing I do (after I “triage” the mower anx determine what to fix and what to scrap) is change the oil, so I can’t speak from personal experience.

I’d guess, though, that the mower wears excessively from neglected oil. …then the excessive play in the mower makes it, effectively, need a very high-viscosity oil. Once you put lube in that resembles oil more than grease, you can’t keep the bearings/journals oil-filled.

So maybe these neglected motors could live a while on gear oil.

I was wondering that myself. I figure the thickest gear oil possible might keep one running a little longer. Either way, I view an engine in this condition as junk whether it can be made to run or not. I figure they should just be considered goners unless it is some specialized piece of equipment. Junk push mowers are everywhere and can be had for free so it isn’t worth spending much time on them. A generator or something a little more unusual is worth a little more effort.

I used to run junkers myself and now don’t mess with them. I do sometimes swap my current good engines that have been well maintained between decks when I wear one out.

In 2002 I bought my son a car my grandma had back in Ohio when she stopped driving. a 1983 Pontiac Bonneville 3.8 v6. We drove it ok from OH to NM then gave it the go-over at 94k miles
Tune up
oil & fluid changes
halogen headlight sealed beams
a few other bulbs
– now, here is a truly grandma driven car that had merely 5000 miles a year on it…
– BUT –
aparently it was also a grandma maintained car too.
Grandma maintained ?
She put gas it and had it washed !
Drove it less and less the older she got therefore paid less and less attention to maintainence in the latter years too.
Don’t know when the last oil change was, it was grandma’s car so we said we’d take it when she offered it.

He didn’t have it but maybe two months and while driving it became harder and harder to go …pedal to the metal and the car just got harder to roll like someone holding back on it with a chain.
He pulled over and called me for assistance.
As we tried to crank it over you could see the crankshaft barely turn 1/4 inch as the starter engaged with a solid , dead end, whunk.

Fresh oil change…engine locked up !

Still don’t know why, we just gave it to my wholesalers.

“so maybe these neglected motors could live a while on gear oil”

Why not. Most motors on lawn mowers and blowers outlast the the rest of the machine when many succumb to rust or worse, hit rocks and stumps and just break. Most of these neglected motors keep running because, even though they are neglected, they are used well below their maximum running time. They would never last the same number of hours when used commercially with regular oil changes. When I brag about my lawn mower lasting 17 years, what I fail to talk about is the actual number of hours of use in a climate it gets stored during the winter. It may be less then the same mower used commercially for just a couple of years in the south, year round or blower used in Northern NY. Unfortunately, we don’t have a true use hour meter on our mowers and only guess at it’s longevity. That’s why, even abused, lawn mower and snow blower motors have a good reputation (undeserved for some) for longevity. I can brag about my 17 year old Toro snow blower but it doesn’t mean squat because it really doesn’t get used much when I shovel all storms under six inches in depth and use the tractor when it’s real deep.

A little off topic, but one of the neighborhood teenage kids was asking me the other day about home-brew go carts and home-brew motorized bicycle conversions, using an old lawnmower engine. Curious, if I wanted to build a go-cart from the typical rotary lawn mower engine, is there a good & frugal method to convert the direction of rotation that comes out of the mower to what is needed to drive the wheels? Somehow it needs to get a 90 degree rotation.

Belt drive with a twist ?
Also, look at the drive on a conventional snow blower with the rear cowling removed. It converts 90 degrees. Don’t know if a snow blower drive gear can be used…but it’s worth using it’s premise.