Oil Change Interval For Seldom Used Small Engine Queston

[PGB1]

Hello All!
The manuals for most of my small engine equipment say to change the crankcase oil at "X" number of hours or annually. One engine is a Honda GX340. It's manual says "X" number or hours or 6 months.

I'm curious why that Honda engine wants 6 months between changes, assuming hours are not reached first. Is it necessary?

I don't know if this is pertinent, but the tank is drained, the engine is run to stall for lack of fuel and the float bowl & lines are drained between uses. (No steel parts) The valve from tank to carburetor is left closed. Fuel always has fuel stabilizer in it.

Thanks for sharing your expertise!
Paul

 

[bertsmobile1]

Honda is being safe
combustion creates acid by-products that end up in the oil where they hopefully are neutraised by the anti corrosion addatives in the oil blend .
Added to that is gravity will cause the heavy contaminants to settle on the bottom of the sump where they form sludge that is difficult to remove and of course water from the air will also condense and drip into the sump.
Prior to the wide spread use of external filters there was a product called "flushing oil" so an oil change was a 2 stage process. drain the original oil. refill with the flushing oil run the engine then drain the flushing oil & refill with running oil.
Large stationary engines will often have running oil & sitting oil particularly if they have external oil tanks

 

[PGB1]

Thank You Bertsmobile1 for taking time to reply & explain.

Do you think after the engine oil is changed the only run time before the 6 month deadline was 20 - 30 minutes of maintenance running I'd be safe to extend the oil change interval to 12 months? (The GX340 is on a generator, so usually it only gets 3-month maintenance runs between 6 month changes. If I use it for a project or a power outage, I change the oil after the use.)

Thanks Again For Helping!
Paul

PS: (Not really related to mowers or small engines- Simply nostalgia of which Flushing Oil reminded me)
Your mention of Flushing Oil reminded me of my 1964 Nova Station Wagon & 68 Buick. One could buy what was called "Re-refined Oil" which was cleaned up used oil. It was really inexpensive.

I'd drain the engine oil, add 2 quarts of this re-refined, plus a quart of kerosene- or if I was rich that week- I'd use VMP Naphtha instead of kerosene. Then I'd idle the engine until hot, drain the mix, swap filters and fill with fresh oil.

The theory was that the kerosene or naphtha in the oil would help it loosen & suspend the gunk for draining or catching in the filter. When I had to change the oil pan gasket & dropped the pan, I was amazed that there was none of the usual black jello on the bottom of the pan. Maybe the concoction worked?

Lots of "Old Days" methods, like Flushing Oil, are now lost. Perhaps it's because they caused damage or perhaps because someone found out how to make money by selling something.
Radiator leaks were sealed with filings from a scrap of copper or ground black pepper and an egg. Automatic transmission slipping was temporarily fixed with a teaspoon of salt. (I know that one had to do damage.) Power Steering pump leaks were fixed with a tablespoon of partly dried, thick oil paint, which was also good for a thread sealant and thread locking compound.

For recycling the old oil, shops would pay something like 5 cents a quart. I think road spraying companies paid for it too. But Detroit had paved streets, thus no spraying companies were nearby. (I wonder how much lead was sprayed on the roads back in those days. Good old days? Perhaps not.)

 

[bertsmobile1]

We invented stable detergents that both hold the crud in suspension and prevent what did not get removed by the filter forming mud in the bottom of the sump.
Kerrosene is actually abrasive .
Nothing wrong with re-refined oil, that is basically what semi-synthetics are but the oil companies did such a good job circulating total BS about re-refined oil that it failed on the retail market .
Ships, trains , mines all use re-refined oil as do some trucking fleets where sump capacity is measures in gallons not quarts .
Oil can be reused indefinatey all you do is filter , break it down into the individual molecules , adjust if needed then reassemble .
This is what is done to make semi-synthetic oil , bakers flour , pastry flour, most margurines and a massive amount of bulk products we all use daily.
However in many cases it is cheaper to start with raw crude oil
Raw crude is chockers will all sorts of stuff , like sand & other rock minerals , water and heaven only knows what else so is often far dirtier than used engine oil .
However the US $ is heavily dependent upon oil futures to retain it's value so there was little to no support for any business that circumvented the futures market .
When the BS trade embargos were inflicted upon South Africa the oil companies there, mostly Shell & BP had no problems re-refining oil hundreds of times for diesel engines
Cars had to run gasahol or e-85 as it is called now and again they ran fine after some rubber parts were replaced .


If you run you generator 3 or 4 times a year then annual or even bi-annual oil changes would probably be fine provided you do not get a lot of water in the oil ( turns it milky )
I wish some of my customers would do that and the same with their fire pumps

 

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