Why do oils like 5w-30 cause increase consumption?

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I read all the time that using an oil like 5w-30 in a lawnmower will cause increased consumption. However, I’ve never heard the “why” . Why does this happen?
 
I think itt's due to the combination of the heat of a small engine and 5w30 being thinner. I always use HD 30 since the manual calls for it in warmer weather and it rarely gets below freezing where I live. (not that I mow during the winter) I would use 5w30 if I had extra but with three vehicles that use it, I rarely do.
 
I have been running synthetic 10w-30 and 5-30 for the last couple of years since I now have a blower on my 318 and it doesn’t get enough use to warrant changing it twice a year. It consumes more than the straight 30 I used to run. I won’t say that they are thinner oils but they flow better letting them get through the known pass through areas easier than straight 30.
 
Originally Posted By: TheLawnRanger
I think itt's due to the combination of the heat of a small engine and 5w30 being thinner. I always use HD 30 since the manual calls for it in warmer weather and it rarely gets below freezing where I live. (not that I mow during the winter) I would use 5w30 if I had extra but with three vehicles that use it, I rarely do.


Partially correct. A 5w-30 is not thinner than a 10w-30 or a 30wt at operating temprature. The reason 5w-30 may see an increase consumption is because they have to use viscosity improvers, this in return makes the oil a little more volatile than a 10w-30 and a 30wt. The general rule of thumb is the wider the difference from Xw and the XX (Xw-XX) part, there is a potential for the oil to be more volatile. The HTHS is also typically higher on a 10w-30 and 30wt vs a 5w-30. This because the oil does not need as many viscosity improvers.
 
I use PP 5w30 in my 24HP B&S mower and have not seen consumption over 100 or so hours. Oil doesnt turn brown either.

No problems for me.
 
Originally Posted By: volk06
Originally Posted By: TheLawnRanger
I think itt's due to the combination of the heat of a small engine and 5w30 being thinner. I always use HD 30 since the manual calls for it in warmer weather and it rarely gets below freezing where I live. (not that I mow during the winter) I would use 5w30 if I had extra but with three vehicles that use it, I rarely do.


Partially correct. A 5w-30 is not thinner than a 10w-30 or a 30wt at operating temprature. The reason 5w-30 may see an increase consumption is because they have to use viscosity improvers, this in return makes the oil a little more volatile than a 10w-30 and a 30wt. The general rule of thumb is the wider the difference from Xw and the XX (Xw-XX) part, there is a potential for the oil to be more volatile. The HTHS is also typically higher on a 10w-30 and 30wt vs a 5w-30. This because the oil does not need as many viscosity improvers.


^this drop that science, son. It cracks me up when someone's or so and so's car that needs a 0w-20 gets 0w-30, 5w-30 recommended to them or worse, 10w-30. This 0w-20 I use doesn't budge on the dipstick. Neither the Honda OEM 0w-20 or the Idemitsu although I just put that in.
 
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The thinner oil sneaks past the piston rings and upward into the combustion chamber to be burned.

Plain and simple and don't take a whole paragraph to explain.
 
Its because ILSAC has/knows (also) conventional 5w30...on the other side of the pond we have synthetic ACEA counterparts with HTHS 3.5min!

Yes you can get synthetic ILSAC variant...but it would be still with HTHS below 3.5
smile.gif
 
I think the possibility of higher oil consumption is referring to 5w30 conventional oil and NOT 5w30 synthetic. Here in FL I run 10w30 synthetic blend in my 20 HP B&S twin and notice no measurable consumption in 40 running hours. Ed
 
That chart was sobering.
I got the idea to use straight 40 in my near 40 year old Sensation lawnmower with a Briggs & Stratton 3.5hp w/rotating valve engine.
Seems OK but I'll try throwing 5W-30 in it next time I run it.
 
I'm not convinced they do cause higher oil consumption (specifically) but the vapour temperature will indicate when any given oil formula will generate blow-by gases and that is a consumption effect.
 
My Ferris ZTR has the B&S 28HP Commercial Turf engine. It has always had RP HPS 5/30 in it, never burned a drop but it only has about 90 hours on it.
 
Originally Posted By: Kira
That chart was sobering.


Yup, 5W-30 conventional oil is only good enough for temps up to 40 degrees F!!!

It seems they've learned the same thing I have. Thin dino oils do not properly protect hard working air cooled engines. I lost 2 Honda powered water pumps this way. Using Pennzoil 5W-30 in South Florida.

Here is South Florida, mower oil temps regularly reach 260+ deg F. That's high enough to warrant an oil more robust than 5W-30 automotive oil.

After a mow:

RtqUiBX.jpg
 
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It's usually because the 5w30 can slip past the worn rings/lose tolerances easier. Most small engines burn oil because they have been neglected, are well worn, or the piston rings don't seal very well.

A customer of mine has an old Briggs and Stratton flathead on a riding mower. It burns conventional 5w30 like it was water, Rotella T 15w40 slows it down a bit.

My Toro Recycler mower I've owned since new, and it can go all season without burning a drop of 5w30. Most of my customers I change their oil with HDEO because it burns off slower, and 99% of them never check the oil.
 
Conventional 5w30 might...but synthetic 5w30 won't...I have been running PP 5w30 for over a decade on a 1980's mower and it still runs strong with no consumption.
 
Originally Posted By: Cujet
Originally Posted By: Kira
That chart was sobering.


Yup, 5W-30 conventional oil is only good enough for temps up to 40 degrees F!!!

It seems they've learned the same thing I have. Thin dino oils do not properly protect hard working air cooled engines. I lost 2 Honda powered water pumps this way. Using Pennzoil 5W-30 in South Florida.

Here is South Florida, mower oil temps regularly reach 260+ deg F. That's high enough to warrant an oil more robust than 5W-30 automotive oil.

After a mow:

RtqUiBX.jpg



I assume that motor has no oil cooler on it? The B&S commercial turf motors have an oil cooler
 
I wonder if some of the additional consumption is caused by the looser tolerances of air cooled engines permitting thinner oils to blow past the rings until the engine gets to temperature?

Personally, I've found that some engines consume oil no matter what you put in them. The 305cc B&S Koolbore I had on my Simplicity snowblower used oil from brand new and for the seven years I owned it. It would use about six oz. every 15-20 hours or so of pretty hard work. Something that certainly needed to be watched. Most other engines I've owned, other than my Yamaha generator didn't burn any oil, no matter what oil I used. My brand new Yamaha EF2000is used oil for the first 900 hours of use then it virtually stopped consuming oil.

My preference for OPE is HDEO 15W40 - 5/10W30 blended 50-50.
 
Non of my OPE(riding mower with 21HP B&S, power washer with B&S engine, and my 5KW gen with a Subaru engine) use oil with M1 10-30.
 
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