Straight 30 or 15W40 for hard use air cooled small engine?

[MSCH]

In this case it does matter. See SAE J300. HTHS of 2.9 vs 3.7 matters a lot in high temperature / high load applications. Just ask CUJET about all the rod failures on generators running 5w-30 after hurricanes in Florida. 5w-40 is just a 5w-30 on mild steroids; it's not anything close to a straight SAE30.

I like 15w40 but I don't think any of these engines are picky, contrary to what anyone else has to say.
usually have 15w40 laying around extra, but I wouldn't go out and buy something special for any of my small equipment.
Then again, I hardly ever change the oil in my generators or pressure washer as they only run a couple hours a year.
Lawntractor gets it once a year.

 

[kschachn]

It's not about being "picky", it's about ensuring adequate MOFT for the expected operating temperature. Those Florida generator engines ran hot and the oils being used were unable to provide sufficient film thickness.

 

[MSCH]

It's not about being "picky", it's about ensuring adequate MOFT for the expected operating temperature. Those Florida generator engines ran hot and the oils being used were unable to provide sufficient film thickness.

I'm in FLA... neighbor has been thru 3 generators in 3 hurricanes... he runs em out of oil. He's a dummy.
and that is probably the most reasonable reason most small engines fail, not because of viscosity but because of no oil at all.
my 2 cents..

now to get back to original question, I'd suggest 15w 40..

 

[kschachn]

I'm in FLA... neighbor has been thru 3 generators in 3 hurricanes... he runs em out of oil. He's a dummy.
and that is probably the most reasonable reason most small engines fail, not because of viscosity but because of no oil at all.
my 2 cents..

now to get back to original question, I'd suggest 15w 40..

Yeah @Cujet noted in his posts that despite many of the generators having a low-oil shutoff they still failed.

 

[Cujet]

The post hurricane generator failures were almost universally on 5w-30, as required. most have low oil sensors. It was stagnant hot and humid air, coupled with 24/7 high load operation. Such as a 4500W water heater on a 5000w gen.

I had 2ea Honda powered water pumps fail on the required oil. The dealership covered the engines, as they only made it a couple of days each. The idea that an air cooled engine without an oil cooler or oil pump, run on 5W-30 automotive oil, at near 100% of rated output, on a hot and humid day, can hold up with 270+ degree oil temps is just incorrect.

 

[oil pan 4]

I use Mobil1 v-twin 20w-50 oil in my pressure washer.
I stuck a thermometer oil cap in it and observed 260f oil on a nice 80F day. On a hot 100f day the oil could easily hit 280f.

 

[oil pan 4]

the post hurricane generator failures were almost universally on 5w-30, as required. most have low oil sensors. It was stagnant hot and humid air, coupled with 24/7 high load operation. Such as a 4500W water heater on a 5000w gen.

When a consumer grade generator is rated for say "5,000w" if you read the manual they're only supposed to maintain that power level for a short period of time, like 5 minutes max. The max continuous load is usually going to be about half of what it's "rated for".
Also with my pressure washer, the hardest running little engine I run, it runs max speed at wide open throttle and hits 260F on a nice mild 80F fall day.
Generators running near max load for most of a tank of gas at a time are probably hitting close to 300f.

 

[IndyIan]

The post hurricane generator failures were almost universally on 5w-30, as required. most have low oil sensors. It was stagnant hot and humid air, coupled with 24/7 high load operation. Such as a 4500W water heater on a 5000w gen.

I had 2ea Honda powered water pumps fail on the required oil. The dealership covered the engines, as they only made it a couple of days each. The idea that an air cooled engine without an oil cooler or oil pump, run on 5W-30 automotive oil, at near 100% of rated output, on a hot and humid day, can hold up with 270+ degree oil temps is just incorrect.

Humid air actually allows more heat transfer, but your point still stands, 5W30 may not be enough for some small engine applications. I think in Florida a better question is straight 40 or 15W40 for your small engines.
I get away with 15W40 in -10C to -15C in the tractor and atv with no starting aids. The snow blower has 5W30 synthetic in it, as its not electric start and doesn't get run above 1 or 2C. My old riding mower gets finish the bottle on the shelf oil though, as its not really run that hard consistently.

 

[Braapdaddy]

I started out with 8 generators but one fell victim to a tree in the ice storm and my highest hour unit aprox 1200 hours rattled its frame apart on one of its last rentals so those 2 be came my parts donors for the others

Zero oil related issues or failures on the 15w40 plus I have no real control over the time a customer runs the unit other than going out to check on it after a few days

I believe the longest run was somewhere over 200 hours logged on that oil unintended ....

 

[z71bill]

I am focused on hot weather - I have plenty of 5W30 and 10W30 full synthetic for cold temperatures.

I have 12 quarts of 15W40 and 8 quarts of straight SAE 30 on hand.

Plus 4 quarts of 5W40.

Wife needed a few things at Walmart so I went along - I let her go her own way and I usually end up over in the oil section (I bet I am the only one that does this even when I don't really need any oil).

They had a giant display of Rotella, both SAE 30 and 15W40 -- I was surprised the SAE 30 cost $2 more than the 15W40. My guess is they sell 10X more 15W40 and it has more competition from other brands.

Do I have enough oil to last a nasty power outage? I think I do but I noticed a small space in my garage oil cupboard and it needs to be filled with a gallon jug of something!

The SAE 30 is calling me - LOL

 

[MSCH]

The post hurricane generator failures were almost universally on 5w-30, as required. most have low oil sensors. It was stagnant hot and humid air, coupled with 24/7 high load operation. Such as a 4500W water heater on a 5000w gen.

I had 2ea Honda powered water pumps fail on the required oil. The dealership covered the engines, as they only made it a couple of days each. The idea that an air cooled engine without an oil cooler or oil pump, run on 5W-30 automotive oil, at near 100% of rated output, on a hot and humid day, can hold up with 270+ degree oil temps is just incorrect.

maybe the idea that running a small engine at or near 100% of its capability for a long period of time and expecting it to hold up is unreasonable expectation. Do you think it would make much difference if they use a higher viscosity oil?

I have 2 gensets.. a 8000W with a honda engine, house is prewired thru a transfer box to 6 circuits. 3 are the well which is intermittent use, the other circuits are just the fridge, freezer, a few lights and wall sockets.. thing runs at about 20% of its rated capacity during hurricane duty..

als have a Predator 3500, which I use for the RV... sleep in the Rv during hurricane blackouts. Predator is only working about 25% running the Ac in the RV.. other than the surge when the AC kicks in.. I don't think either of them are overowrked.

so maybe it is the use pattern of the end user having an undersized generator causing the problem, more than the oil.

 

[MSCH]

I am focused on hot weather - I have plenty of 5W30 and 10W30 full synthetic for cold temperatures.

I have 12 quarts of 15W40 and 8 quarts of straight SAE 30 on hand.

Plus 4 quarts of 5W40.

Wife needed a few things at Walmart so I went along - I let her go her own way and I usually end up over in the oil section (I bet I am the only one that does this even when I don't really need any oil).

They had a giant display of Rotella, both SAE 30 and 15W40 -- I was surprised the SAE 30 cost $2 more than the 15W40. My guess is they sell 10X more 15W40 and it has more competition from other brands.

Do I have enough oil to last a nasty power outage? I think I do but I noticed a small space in my garage oil cupboard and it needs to be filled with a gallon jug of something!

The SAE 30 is calling me - LOL

View attachment 186410

you are good with either oil you choose.

 

[z71bill]

maybe the idea that running a small engine at or near 100% of its capability for a long period of time and expecting it to hold up is unreasonable expectation. Do you think it would make much difference if they use a higher viscosity oil?

I have 2 gensets.. a 8000W with a honda engine, house is prewired thru a transfer box to 6 circuits. 3 are the well which is intermittent use, the other circuits are just the fridge, freezer, a few lights and wall sockets.. thing runs at about 20% of its rated capacity during hurricane duty..

als have a Predator 3500, which I use for the RV... sleep in the Rv during hurricane blackouts. Predator is only working about 25% running the Ac in the RV.. other than the surge when the AC kicks in.. I don't think either of them are overowrked.

so maybe it is the use pattern of the end user having an undersized generator causing the problem, more than the oil.

I like staying under 50% rated load - the excess above that is for starting things up like the HVAC fan. Course in a pinch I would run it as hard as I needed to - I have a backup generator.

Expecting a 3000 watt unit to run close to max for hours and hours is not a good plan.

That said using 5W30 oil in hot Florida temps running close to max load and going several days between oil changes is just plain dumb.

Most of these small units take 1/2 a quart or less - why push the oil change interval to save < $2?

 

[bchannell]

Don't overthink it, either will keep it running for a long, long time.

 

[awguy]

I'd use whatever the owner's manual says but full synthetic.

 

[z71bill]

I'd use whatever the owner's manual says but full synthetic.

Owners manual is misunderstood - it isn't recommending the best - it is setting the minimum requirement that you must do to keep the warranty. Which is not very long. My generator - purchased new - sat in the box unused until one month after the warranty expired.



Doing what is in the owners manual is like telling your kids to do the minimum amount of homework just so they get a C?

IMHO synthetic oil is GREAT in some applications - my generator recommended oil change interval under constant use in high temps is every 24 hours- I change it at least every 24 but usually before - if convenient.

I think the difference between synthetic and regular oil with 24 hour change intervals is insignificant as far as wear - but could improve gas consumption - factor in how expensive synthetic SAE 30 is and it is not worth it - I have some semi synthetic 15W40 that I grabbed on clearance for cheap - I don't recall - $12 a gallon??

Manual says 5w30, 10W30 or straight 30 weight -

If you think 5w30 synthetic is a better choice than a diesel rated non synthetic SAE 30 / 15W40 turn in your Bob is the oil guy badge and exit the in back of the building. LOL Just kidding.

 

[fantastic]

Wife needed a few things at Walmart so I went along - I let her go her own way and I usually end up over in the oil section (I bet I am the only one that does this even when I don't really need any oil).

My wife knows the drill & will say to me "I'll meet you back in the oil section" . Got to stay up to date on the latest changes..If any .

15w-40, 5w-40, or Full Synthetic 10w-30 is what I run in small engine stuff.

 

[Rogueman2016s]

Amsoil has a good oil for outdoor power equipment and small engines. Straight 30wt would be my choice

 

[dlundblad]

A 5w30 isn’t good enough for hot temps? I think the key would be to keep the oil changed every 50 hrs or whatever is suggested.

In the event of a long term outage, I’m guessing an oil change every 2-3 days isn’t on people’s minds.

 

[Soft Cars]

If the engine is a splash lube engine with a little oil dipper fastened to the connecting rod cap, I wonder if 15W-40 is "splashible" enough.