Viscosity and hours between oil changes in small air cooled engines.

I too have mulled what weight oil to use in my generator and other OPE. I've come to the conclusion that if it's a splash lubed system to use a 5w-30 just because I want the oil quickly flowing down the block to the sump so it can get splashed around again. I don't want a 40 or 50 weight taking more time getting back to the sump to get dispersed again. It's doing no good hanging out of the walls of the block while on it's way down. The main thing is the small amount of oil they often hold. 16 ounces isn't much if it's not getting back to the bottom of the block. To me, a constant flow of thin oil is better than no or a small amount of a thicker oil any day. And since the system isn't pressurized, seems to me that a thinner oil will get into tight areas better than a thicker oil will. Changed every day in extreme conditions should keep it fresh enough to protect the engine. And, I don't trust the low oil cutoff either because I think there would be enough residual oil on the switch to keep it from shutting the ignition off and not necessarily enough to lube the engine. I use Pennzoil Ultra Platinum 5w-30 in all my OPE. Pressure washer, snow blower, push mower, and generator.

As far as pressurized systems, I run Mobil 5w-40. I like the idea of the slightly thicker oil in an air cooled engine but the splash lubed systems just don't hold enough for my liking. And even being filtered and pressurized, I usually run 50-75 hours on a recommended 100 hour change. It's cheap and I change the filter every other time...the manual recommends 200 hours on the filter BTW. On a hot day, I have used my infrared heat gun to measure the oil temperature and have seen as high as 265 degrees for hours on end.
 
When the oil is moderately cold there’s a lot less difference in viscosity that’s you’re imagining between a 30 and a 40-grade, even a 50-grade. When it’s hot that will make zero difference in drain time. And “tight areas” is irrelevant.

Thin oils are never better at protection MOFT always wins.
 
How would tight areas be irrelevant? If a higher viscosity oil can't get in between, say, the piston and wrist pin area and the thinner oil can, then there is going to be metal to metal contact.
 
How would tight areas be irrelevant? If a higher viscosity oil can't get in between, say, the piston and wrist pin area and the thinner oil can, then there is going to be metal to metal contact.
So you’re saying you have some sort of technical proof that this doesn’t occur with say a 40-grade as opposed to a 30-grade? Something other than your feeling that it does not. That the oil molecules are too big to fit.
 
No technical proof other than if higher viscosity always wins then why doesn't every engine just get 100 weight and call it a day. Obviously there is a need for thinner viscosities for tighter tolerances to get lubricated where a higher viscosity cannot physically get into. What I'm saying is that in a non-pressurized oil system, you are relying on oil to get into tight areas via gravity or just parts moving and oil flying around and that's why I prefer a lighter weight oil. I totally agree that a higher viscosity oil is better at keeping metal components apart from each other as long as the heavier oil can get in there. And maybe a 40 or 50 weight oil at 250 degrees can get in there but I'm just not willing to try and like I said earlier, I want that oil to get off the part and back to the sump to get kicked back up by the dipper on the connecting rod to lubricate parts again.
 
I too have mulled what weight oil to use in my generator and other OPE. I've come to the conclusion that if it's a splash lubed system to use a 5w-30 just because I want the oil quickly flowing down the block to the sump so it can get splashed around again. I don't want a 40 or 50 weight taking more time getting back to the sump to get dispersed again. It's doing no good hanging out of the walls of the block while on it's way down. The main thing is the small amount of oil they often hold. 16 ounces isn't much if it's not getting back to the bottom of the block. To me, a constant flow of thin oil is better than no or a small amount of a thicker oil any day. And since the system isn't pressurized, seems to me that a thinner oil will get into tight areas better than a thicker oil will. Changed every day in extreme conditions should keep it fresh enough to protect the engine. And, I don't trust the low oil cutoff either because I think there would be enough residual oil on the switch to keep it from shutting the ignition off and not necessarily enough to lube the engine. I use Pennzoil Ultra Platinum 5w-30 in all my OPE. Pressure washer, snow blower, push mower, and generator.

As far as pressurized systems, I run Mobil 5w-40. I like the idea of the slightly thicker oil in an air cooled engine but the splash lubed systems just don't hold enough for my liking. And even being filtered and pressurized, I usually run 50-75 hours on a recommended 100 hour change. It's cheap and I change the filter every other time...the manual recommends 200 hours on the filter BTW. On a hot day, I have used my infrared heat gun to measure the oil temperature and have seen as high as 265 degrees for hours on end.
You are over thinking this.

The most important factor in a splash lubed system is that the oil level is full. I've worked on small engines for customers going on 16 years now. I've had customers bring me 30+ year old machines with the original oil in them that they have never changed, only added when it was low. The machines might smoke a bit on start-up, but otherwise run fine. Small engines have very loose tolerances, and very little complexity inside. Oil getting into tight spaces isn't an issue like it is on modern automotive applications with hydraulic controlled variable valve timing. You could run anything from a 0w20 to 10w60 and they will be fine as long as there is enough of it in there to get splashed around. Every single engine failure I've seen that was lubrication related the engine had either no oil at all, or had been running very low on oil for quite some time.

My advice to anyone looking for generator oil is pick something that fits your maintenance schedule. If you check the oil every time you fill the fuel tank and plan on changing it every day, then basically anything that is oil will work, preferably something in the viscosity recommended by the manufacturer. If you rarely check the oil, run the generator for multiple tanks of fuel unattended, or work in extreme heat, then a HDEO might be a better choice just because they are less likely to be consumed.
 
Plus if a 40 or even a 50-grade oil couldn't get into tight spaces or was really a problem in cold weather then my 21 year-old snow thrower would be in the scrap heap by now. Sometimes I really wonder how large people think that an oil molecule can be.

The notion that I'm advocating a 100 "weight" oil is just silly and isn't germane to this discussion.
 
I have a +50 year old B&S MontgomeryWard 5HP 2200 Watt generator that I use HD 30 Wt oil in. We used it for 2 weeks in 2009 when we here in Western Kentucky had a massive ice storm. We have 2 homes so it was taken from house to house and boosted freezers for co-workers. Oil was changed once. Still runs good. Put in back to sleep till the next big event. My only complain is that the 3 quart gas tank runs out after 45 minutes.
 
I run 10w30 Full Syn. QS in all my small engine equipment with non ethanol fuel and stabil in every tank. Never had any engine issues and my equipment is always ready to go.
 
The mother of my son in law called me and ask about generators, she knows I have 3 of them - she wanted to buy her son a generator for Christmas.

I gave he a few choices - she picked a 3500 watt inverter - should handle what they need.

I decided a good Christmas gift for my SIL would be "everything else" he would be needing to hook his new generator up to his house.

I installed an inlet plug & interlock on his breaker box, and started putting together everything I could think of. Power cord, a few gas cans, spare spark plugs, funnel, siphon pump, fuel stabilizer, oil drain pan, and a few other items -then I got to oil.

The owners manual calls for 5W30 synthetic and straight 30 weight for above 50 degrees (maybe 40) so I grabbed a jug of SuperTech 5W30 full synthetic, a quart of SuperTech HD30 (for break in) and a few jugs of Pro-Select SAE 30 4 cycle. The Pro-Select is Lowes house brand and is designed specifically for 4 cycle air cooled engines.

After looking at the Pro-Select oil I decided to buy some for myself too.

I now have these oils on had for generator and lawn mower use.

SuperTech 5W30 full synthetic
SuperTec HD30 conventional
M1 5W30 full synthetic
Chevron 5W40 full synthetic
Chevron 15W40 synthetic blend
SuperTec 15W40 conventional
Honda 10W30 conventional
Pro-Select SAE 30 conventional

So no matter what - I should have something to use to keep my generators running form below zero to over 100 degrees!
Yes I over think stuff --
 
I've 2 generators. Choose your full syth. oil viscosity on ambient temps. My Generac 10k unit needs to start at -30F in winter. All-time record high at its location is 92F. It gets 0-30w M1. It has an oil cooler, so I'm not worried about avg. summer high temps in the low '80's.
The portable BS powered unit it replaced was impossible to pull start at 0F with 5-30W in it, you could only pull start it with a 0 bottom number oil in it. 5-30w pulling the recoil would lift it off the ground and not spin it fast enough to start.
My other BS powered unit gets 5-30W ST synth. in it as its stored in a warm garage.
Generac running on propane is 8 yrs. old zero issues, serviced via its monitor. BS powered Craftsman 5600w is 18 yrs. old now and ran 11 days straight after Hurricane Sandy. Fires right up and stored on stabilized E0 gas. In storm conditions it gets whatever gas is available when my E0 supply is depleted.
Manufactures get to torture test their motors so we don't have failures so go by the temperature range recommendations for viscosity.
Everyone tries to overthink the manufactures testing, don't, they have blown up more motors than we have owned.
Good oils changed on schedule and good fuels will never let you down.
 
My generators operate in temps from -30F to 90F+, I typically change the oil every 75hrs which just happens to be about one full weekend of use. I use the same oil year round, either a 0W-40 or a 5w-40 depending on what I have enough of on the shelf. Lately it's been more 0w-40 since I sold my diesel truck. A typical weekend for my 3500w generator has a load of 1000-2500watts nearly continuously and I don't shutdown till Sunday afternoon, I use an extended run system and refuel on the run. Never had an issue with my oil, doesn't burn any, oil doesn't seem sheared down, color is barely darker than new.

In a nutshell, pick a decent oil and use it. Doesn't really matter what it is. Change it regularly but it doesn't need to be changed every 20hrs, most inverter generators with some form of eco mode recommend 50-70hr oil changes. These motors do not run full tilt like the older generators, they are much gentler on the oil running at 1500-2000rpm's than an older generator running at 3600rpm's full time.
 
Personally I find myself uncomfortable with the lack of specifications on Pro-Select products.
Says SL SJ SH right on the bottle.

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Says SL SJ SH right on the bottle.
Good catch! I was thinking of the 2-cycle oils that have no JASO ratings. Lowe's sells Pro-Select with no rating, Craftsman with JASO FB rating , and Husqvarna with JASO FD rating. All of the pre-mix sold there is also FD rated.

Getting back to your observation, I have to say that it has been a long time, five years or more, since I have had API SL rated oil lying around. Much of what has changed since SL has to do with fuel economy and extending the life of catalytic converters. Neither of those things are particularly relevant to OPE.
 
Why not tune the motor to how it should run, vice what the national boards say? What causes heat most in a Gas 2/4 stroke? Combustion, then friction, than ambient. Richen that mixture a bit, you’ll find running a 30 weight of any sort will be the best balance as higher weights retain more heat. More heat requires the need for large/increased cooling options (large fan over fins, larger oil cooler, etc).

Do your motor a favor and don’t put a bandage on a problem. Why not fix it at the source? We all should know that these more modern engines run to the edge of lean. Fix that, and your WHOLE motor will be happier. So will your brain trying to bandage instead of fix.
 
It has the GC190 engine.

It says in the owners manual - never use gasoline mixed with oil. 125:1 is pretty close to no oil - but still gives me a pause.

I have considered the 10W30 diesel rated oil a few times.

The 10W30 diesel oil with a SJ or better rating is not easy to find -

All good info - I have 5W40 and 15W40 diesel oil on hand - but in my change the oil every day system are they really better?


Let’s lean out the mixture even more by adding “No” oil….sounds like a great, and prudent plan to add even more heat related shearing.

Try 275-300:1 instead along with richening all three circuits of the carb. Or run some leaded and do a tear down to see if you really needed to help the upper cylinder/head…..

Scientific, Methodical, Tried and True, Common Sense should dictate
 
But this stuff interests me - and curiosity makes me want to figure out what is best.
Far as a 50 weight oil - no way I will do that unless it is something the manufacturer recommends -
First off, the viscosity of the oil is not going to dictate the change interval. The quality of the oil is.

Constant running under load is akin to highway driving; changing every 20 hours is a waste of good oil, and is similar to changing your car's oil every 1200 miles (20 hours X 60 mph as an estimate). You said it was not an issue to change the oil while refueling, but changing every time during a long outage while worrying about if your oil is good or not will be tedious.

To be certain of the oil's condition you need a UOA. Anything else is guesswork, and with this being an emergency generator you don't want to guess. Since you want to figure it out, maybe it's best to use science rather than opinion to do so. As tnt_motorsports said, he is running 100 hours and using UOAs.

In your position, Houston in summer, I would pick a good 15w-40 synthetic. Run it for 20 hours and send in a sample, gradually increasing the hours used according to the UOA results. I would bet that you could safely get up to at least 100 hours between changes.

For Winter, the 15w should be fine unless Houston's record low temperatures of negative degrees F are approached. In that case I would consider 5w-40.

As far as oil brand choice, there are numerous good ones out there; but since you're concerned with the durability of the oil and price seems to not a concern, why not go with an oil designed to be run further? I would use Schaeffer, but for example Amsoil is good as well.

Lastly, in order to be prepared I'd be running the generator now or in early spring, to get the testing out of the way and have the chosen oil installed and the interval set prior to hurricane season this summer.
 
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We have Honda generators at work that aren’t abused necessarily, but they are definitely used the way they were designed to be used. Construction like settings. Extreme cold and heat in all sorts of not so ideal conditions with heavy loads. Sometimes they only run for a few mins and other times they’re on for a day. They always start on the first or second pull too. Very impressive little machines.

5w30 “house brand “synthetic is all they see at their factory suggested intervals. Following that is the key IMO. Say it’s 50 hrs for conversation sake… in the event of an outage, I’m sure an oil change is the last thing people think about when the power has been killed for a week.

I realize this is BITOG and we do overthink things. If it were mine, id use either an A3/B4 or HDEO synthetic with some on hand in the even of an emergency, but wouldn’t hesitate to use whatever is on hand should the need arise.
 
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