LAWNMOWER OIL VISCOSITY

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931
Location
Michigan
My .02 on viscosity: Lawnmower oil (especially that used in tractors)in my opinion ought have a far higher viscosity or weight than an automobiles because as oil gets hotter, it gets way thinner in aircooled engines. As we know common car oil has been 10W-30 (not too long ago). This allows the oil in hot temperatures to go no lower than ten-weight and no thicker in cold temperatures to 30-weight. This would never do in a Harley for example or in my opinion a big V-Twin tractor engine, as the oil would be so thin the bearings would wear out in no time. Tractors needs heavier oil since the engine always runs warm. That's why in my tractor's V-Twin I have run either a 30wt conventional for break-in or a 15W-50 PAO or Diester oil. 10W-30 synthetic's are probably great for a 21" mower.. but beyond that my money is on a 15W-40 or 15W-50 and maybe even a 20W-50. Thanks for taking the time to read this and my experience is based on UAO's that took time and $$$ to prove the point to myself if nobody else. The one time I used a 10W-30 in the V-twin it consumed oil and the UOA was crummy.
 
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5,215
Location
Houston, Tx, USA
Anymore it's xW-40 or xW-50 for me. HDEO's only. I choose either 5W-40, 0W-40, 15W-50 or 5W-50 synthetic or a 15W-40 conventional. If I'm changing the oil for somebody else (who might not change it as recommended), I go straight HD-40 for it's shear and consumption resistance.
 
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Messages
6,070
Location
northern Alabama
 Originally Posted By: Pete591
[snip]As we know common car oil has been 10W-30 (not too long ago). This allows the oil in hot temperatures to go no lower than ten-weight and no thicker in cold temperatures to 30-weight.[snip]
huh? Someone needs to review the basics.
 
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1,373
Location
Somerset County, PA
 Quote:
The one time I used a 10W-30 in the V-twin it consumed oil and the UOA was crummy.
I noticed what seemed like more oil smoke than normal at startup (25 HP Kohler v-twin) when using 10-30 Rotella dino, but it didn't consume more than usual. I pretty much use that or straight 30 (usually Rotella T) in everything that's summer-use only. For snowblowers, it's M1 5-30. The diesel stuff gets RTS 5-40 or J-D 0-40 year-round. \:\!
 
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1,093
Location
Kentucky
 Originally Posted By: benjamming
 Originally Posted By: Pete591
[snip]As we know common car oil has been 10W-30 (not too long ago). This allows the oil in hot temperatures to go no lower than ten-weight and no thicker in cold temperatures to 30-weight.[snip]
huh? Someone needs to review the basics.
This is a joke, right? No one who has been on BITOG for almost a year with 400+ posts could still know nothing about motor oil. I think this is just If I am wrong and you rally do not know, I apologize and highly recommend you read lots of other posts for a while.
 
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7,742
Location
MI
FrankN4, I saw that and scratched my head also. Pete, your oil choice doesn't jive with small engine manufacturers or about 90% of the professional lawn contractors that post over at lawnsite.com. They are putting thousands of hours of use on their mowers, most with 30w or 10w30, per Kawasaki/Kohler recommendations. Now, here's a hypothesis for some expert to answer. I have been told that going from a 90w gear lube to a 140w gear lube in a gear box will cause it to run hotter due to the increased "friction?" of moving that thicker oil around. Would this idea hold true in an air cooled engine? It runs hotter trying to move that thicker 15wWhatever around? Maybe a bad thing? Less power, etc.. Maybe a 15w40 at higher temp is the same viscosity as a 30 weight at lower operating temps?
 
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5,069
Location
Saratoga, NY
Pete591, i don't know if I'm explaining this correctly, but a 5W-30 oil should be explained something like this: At freezing (0 Celsius/32 Fahrenheit) the oil acts like a 5 straight weight. At boiling point (100 Celsius/212 Fahrenheit) the oil acts like a 30 straight weight. Of course, there is a lot of play in those numbers and viscosity stability is a whole other issue. 5W-30s quickly become 5W-20s in harsh applications. I used a 15W-40 for most OPE in the summer when I looked after Dad's equipment. On cool mornings, it cranks over better than a straight 30 (and Briggs & Stratton are now saying straight 30s can damage your engine in freezing temps) and once the engine is at temp, it acts like a 40 weight ... just a tad thicker than the straight weights used for years ... but with a killer add-pack to deal with heat, fuel contamination, etc ...
 

Pete591

Thread starter
Messages
931
Location
Michigan
 Originally Posted By: Bror Jace
Pete591, i don't know if I'm explaining this correctly, but a 5W-30 oil should be explained something like this: At freezing (0 Celsius/32 Fahrenheit) the oil acts like a 5 straight weight. At boiling point (100 Celsius/212 Fahrenheit) the oil acts like a 30 straight weight. Of course, there is a lot of play in those numbers and viscosity stability is a whole other issue. 5W-30s quickly become 5W-20s in harsh applications. I used a 15W-40 for most OPE in the summer when I looked after Dad's equipment. On cool mornings, it cranks over better than a straight 30 (and Briggs & Stratton are now saying straight 30s can damage your engine in freezing temps) and once the engine is at temp, it acts like a 40 weight ... just a tad thicker than the straight weights used for years ... but with a killer add-pack to deal with heat, fuel contamination, etc ...
I had it a bit turned around. It does seem like a 15W-50 or 15W-40 offers better starting protection than a 30wt with better heat and maybe shear "cushioning" as well. I will maybe try a 10W-40 next time.
 
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4,252
Location
Central Wisconsin
Was told some time ago that 10W-40 was a no-no. Not sure why. I recall being told that it sludges more than other weights. Japanese motorcycles used it for years until they got their own oil brands. Some still call for the 10-40. 15W-40 works so well, I would think 10-40 would too.
 
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5,069
Location
Saratoga, NY
10W-40 is often not recommended because it was one of the first widely-used multi-weights. And early formulations had really terrible viscosity index improvers. In the real world, these would shear down and produce a mess of sludge in engines. It got a bad rep it's still trying to shake decades later. Newer 10W-40 oils (probably SG or newer) should be fine. In OPE applications, 15W-40 has the advantage in add pack (HDEO vs. PCMO) and shear stability. 10W-40 would have the advantage in cold weather pumpability.
 
Messages
15,056
Location
Canada
I think GC or XD-3 would make a great oil for OPE....strong base oil mix that is heat and shear resistant, and strong detergent/dispersant amounts to keep engine clean. Also, good in cold weather IF needed (snowblowers). GC gets the edge here a lot, as it is sold in quarts/liters, and is easy to get at most stores. So that's what I'd put in any equipment I had.
 
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3,338
Location
Kansas, USA
He could be right. Put Havoline 5w30 in my push mower to replace the PP 5w20. After 15 minutes in this 90+ degree heat it started smoking slightly, better than the 5w20 though. If you pulled the dipstick you'd think it was boiling water. Replaced the Hav 5w30 with Rotella 15w40 and although it still steams a small amount out of the dipstick nothing visible on the outside. It is overfilled a bit.. thanks to Briggs and Stratton not knowing how much their own engine capacties. If that even affects it any.
 

Pete591

Thread starter
Messages
931
Location
Michigan
 Originally Posted By: Eric Smith
He could be right. Put Havoline 5w30 in my push mower to replace the PP 5w20. After 15 minutes in this 90+ degree heat it started smoking slightly, better than the 5w20 though. If you pulled the dipstick you'd think it was boiling water. Replaced the Hav 5w30 with Rotella 15w40 and although it still steams a small amount out of the dipstick nothing visible on the outside. It is overfilled a bit.. thanks to Briggs and Stratton not knowing how much their own engine capacties. If that even affects it any.
I do know that with 5W's and 10W's my UOA's were not nearly as good as when using a PAO or Diester 15W-40 or 50. Amsoil 15W-40/Redline 15W-40/Motul 15W-50/M-1 15W-50 have worked best in V-twins I have tested and also in Tec's and B&S small engines with no visible sheen in the oil like we have been hearing about lately. A high ZDDP conventional oil like Bradd Penn is also a winner. I also use Motul 5W-40 in my 9HP Honda smow Blower with near zero wear numbers. It wold be nice if we had more UOA's posted here for small engines. If properly lubricated a small engine ought last 25+ years of contimuous service. Look at the old Lawnboys...I know of some that are this old. It's all about fresh clean lubrication and frequent changes.
 
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2,488
Location
MN
I have been using 5W30 Synpower for years with no problems in my 6.75HP B&S. It was 95+ yesterday and I got no smoking or consumption. I change every fall before putting it away for winter.
 
Messages
1,007
Location
Dallas, TX
Instead of following an owner's manual to the letter, experiment to see what your mower likes. As far as Briggs is concerned, I should be using Briggs 30W in my 6.5 Troybilt. I broke it in with that, but then switched to a 5W-30 syn, which it consumed at a rate I wasn't comfortable with. I switched to 10W-40 syn, consumption slowed, but I wanted it stopped. It now runs 20W-50 syn and consumption is nearly zero.
 
Messages
77
Location
Florida
The new Toro 20068 came with a 20 oz. bottle of Toro Premium 4-cycle lawnmower oil. Manufacture date is X-3-30-99. Exxon-Mobil gives a five year shelf life for engine oil.
 

JTK

Messages
13,161
Location
Buffalo, NY
Even back in 1979, Case recommended SAE 30 or 20w40 for the 10hp Kohler K341 in my Case 220 tractor; Joel
 
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