Mixing oils of different viscosity to make a new viscosity for air cooled splash lubricated engines

General Discussion
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Yes it’s another oil thread. I know if oil A is allowed and oil B is allowed, any mixture of oil A and B can be used.

20W-40 is really hard to find. If I mix 1 part 40 and 2 parts 10W-40 will I get something like 20 (partial W)-40? 20 cold - 30 would be a better generator oil than non synthetic 10W30 for mild climates. I assume 10W30 and SAE 30 mixed should make something close. I assume the winter W rating may go away when mixing oil like this. I believe the W rating ensures that the oil can till be poured in low temperatures and not gel up completely, even if it is thick.

Is there a way to estimate or figure out what the resulting viscosity will be? Or should I test it? Making a tube with a hole in it to measure viscosity and putting it in the freezer or heating it up can’t be that hard.

Air cooled engines usually run hot, so non synthetic 10W30 and such should be avoided in the summer to prolong engine life. How hot it runs depends on the engine and load. If the manual says 10W30 can be used it might have more cooling fins and run cooler than others.

Also, single grade mineral oils lubricate a little better than non synthetic multi grade in any engine even if it doesn’t run hot, so there is no benefit to use multi grade in a tropical climate that never gets too cold. In mild climates, 20W30 might be sufficient for winter use. That’s why this topic is important to me.

My understanding is that the following is a very rough guide as to what can be used in splash a lubricated engine.
SAE 50 > 80 degrees F
SAE 40 > 60 F
SAE 30 > 40 F
SAE 20 or is it 20W? 20W-whatever > 20 F
SAE 10W > 0 F
SAE 5W > -20 F or -10 F or such

In the winter oil can get splashed away from the sump and it will cause the low oil shutdown to trigger! So that tells you something! If you have to start a splash lubricated engine below these temperatures I would run it at idle for 10 seconds then let it sit for up to a minute. Then 10 seconds and let it sit for 30. Then again and let it sit for 20. Then again and for 10. Then idle for 30 seconds before going to running speed.

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I am just going to throw in my two cents. I am not a chemist and I barely passed chemistry in high school; But quite honestly, back then there were only three known elements : Fire, Water, and Air… L :smile: L . . .

But over the years, I’ve read a lot on the subject and even some of it stuck (I guess the viscosity was too thick… Another L :rofl: L . . .

But when thinning or thickening by mixing different viscosities could lead to unpredictable changes in the oil consistency. Thinning of thicker oil or thickening of thinner oil may result, compromising the oil’s ability to perform optimally under varying conditions.

All oils have various additives and not all additives may be compatible…

First off, engine components rely on a specific oil viscosity to form a protective layer. By mixing oils with different viscosities could result in inadequate lubrication, leading to increased friction, wear, and potential engine damage.

Next, the mixing could altered Flow Characteristics. The engine oils are carefully engineered to flow at certain rates to reach critical areas. Mixing oils with different viscosities can disrupt this flow pattern, affecting the oil’s ability to cool and protect components effectively. I know Turbos are particularly susceptible to damage from inadequate flow…

Also, by Thinning or Thickening the oil by mixing different viscosities could lead to unpredictable changes in the Oil Filter Clogging. Again, getting back to the additives, some may be so Incompatible that they might form sludge or deposits that can clog oil filters and restrict oil flow.

Then, there are the Warranty Concerns, when you create your own “witches brew” of Oil Stew, you are deviating from the recommended engine oil viscosity specified by the manufacturer and it could void your vehicle’s warranty, leaving you responsible for any potential repairs.

So, my advice is stick to the recommended viscosity and if it’s difficult to find, buy extra when you do find it and do not expect to find in on sale at your favorite discount store… :+1:

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Agreed with sticking to the recommended oil, even if it’s expensive or hard to find.

Kind of reminds me of a gun collector I used to know. He had some unusual guns using unusual calibers of ammo not locally available. He’d often have to order the bullets custom loaded off the internet. But that’s an example of pay to play; don’t go into it thinking it will be easy or cheap.

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Maybe you should try asking these crazy oil questions on an oil forum… lol
Unless already banned from it…

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Are there cars or small engines that call for 20-40? That’s odd. Mine say 5-30 syn or straight 10 or 30 depending on season. Even in the 70s cars took 10-30 or maybe 40 if you lived in the desert. Rotella diesel oil is 15-45 so just use that.

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The owners manual for dad’s Yamaha ATV lists 20-40 as one of the allowed oils depending on the temperature range, For the oil change he bought a kit with 10W40 Yamalube from the dealer.

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Well shouldn’t be hard to locate then by just going to a Yamaha dealer. I suspect wonderful90s though doesn’t want to pay the $10 plus a quart and thus mixing his own from the $3 Walmart variety.

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mixing his own from the $3 Walmart variety.

Would you trust the [[[[[SNOWMAN]]]]] to be able to do that

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I rebuilt a 10 year old air cooled Tecumseh lawnmower engine in 1987 that had an oil pump. I doubt there are any splash lubricated stationary engines that are less than 50 years old. This is a non issue.

As for this ignorant statement…

It should be ignored. It is just wrong.

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I know my lawn mower is splash. I haven’t had the gebpnerstorbor pressure washer apart but they do not have filters so assume they are splash too. I have never had a lubrication problem with the splash systems. It’s important to keep the oil level full and not operate on un level ground though. Think of that Little Dipper at 1000 rpm’s and oil will be splashed everywhere.

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The brass-colored housing is an oil pump driven by an eccentric on the camshaft of a small engine (single cylinder). This is how it was done 50 years ago.

image

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That is what was in my Tecumseh. A little piston pump.

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A lot of small engines are still the splash type, they have just gotten more sophisticated than the old paddle style…

This video is for Briggs and Stratton by Briggs and Stratton…

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Saw that on a Tecumseh lawn mower! That little oil pump brings oil to the upper main bearing on vertical shaft engines.

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Well never had a vert tech, just horizontal snow blower engines. Had several of those apart but never noticed anything but a dipper on them. But it’s been maybe 30 years so could be mistaken. The tech was the best snow blower engine ever but you had to make sure not to run them low on
oil. Got one with the parts in a pail that had blown the rod through the block. A little welding and new rod and ran fine again.

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If you need 20w40, why not just use 20w50? It should cover your needs. But I now use 5w30 synthetic in all my small engines, no problems so far.

15w40 diesel or 5w40 synthetic diesel oil should work if 20w50 is too thick for you.