How hot is too hot?

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Nick R

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Took this today, after an hour of mowing the lawn with the tractor. Grass wasn't particularly super high, but it was high enough. Engine RPM at max is 3100RPM, Briggs 21HP OHV single cylinder.

Thought this seemed a bit hot... Then again, I don't want to know how hot the pressure washer was running, after 40 minutes of full load in the same temps. Temps were around 93 degrees, for the record. Both engines running Rotella T6 5W-40

imag0138ot.jpg
 
I have a dipstick thermometer on my air-cooled BMW twin. It's always above 220 (has a thermally controlled valve that won't flow oil into a radiator when the temperature is lower), and if weather's hot I start worrying only significantly north of 250.
 
That's oil temp right? Pretty much normal. Pretty good actually for 93 degrees. How is it 93 degrees in NY? It only gets up to 85 or so in Houston.
 
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I use 10w30 T5 in my Cub Cadet with a Kohler engine. Most I ever see is like 180 or 190 even after 1.5 hours of mowing. Maybe I'll use my temp gun on it to see if its accurate.
 
My 135i sees this routinely. You're running the right oil for it, though if you really run for over an hour straight, you could consider a straight 40wt. Of course since its cool in ny, the 5w-40 is surely smarter.
 
I wonder what the viscosity of Rotella T6 5W-40 is at 238 Fahrenheit?

If it is less than 10, then I would think that you would want a thicker oil. If it is 10 or greater than the oil is probably still thick enough.

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Regarding oldhp post of "I'm thinking a syn 5W30 would run cooler. What does the manual say to use?"

There have been post here on BITOG about how much cooler an oil of less of a viscosity would run, and the difference is negligible, something like 5 to 15 degree Fahrenheit difference. Certainly not enough of a decrease in temperature to make it worth giving up the extra protection that the thicker oil provides when you run an air cooled engine in hot ambient conditions.
 
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It seems to me your engine should be running at 3600 rpm's instead of 3100! That alone will cause it to run hotter.
 
Originally Posted By: oldhp
I'm thinking a syn 5W30 would run cooler. What does the manual say to use?


A 40 wt oil is not recomended for this engine. I have the exact same mower as yours. I'm using M1 10-30 and even though I don't have a oil temp guage the oil filter never seems very hot to me. Remember a thinner oil will probably run cooler and will be easier on the oil pump. I checked my manual and no where is 40 wt oil called for. Try a quality 10-30 and see what happens. I've been mowing every 4-5 days for 2 months now and and no oil use .
 
Originally Posted By: gman2304
It seems to me your engine should be running at 3600 rpm's instead of 3100! That alone will cause it to run hotter.







+1, not doing it any favors running it that slow.
 
238 F is not that much hotter then 100 C (212 F) the temperature that most hot oil viscosity is specified at. A decent quality mono weight 30 would be less likely to shear compared to a multi-weight. But a good quality multi-weigh xW-30 would also work well.

Years ago I talked to a man who worked on out door power equipment for many years. He said that he had seen many engines that were damaged with multi-weight oils, and he strongly recommended mono weight 30 instead of multi-weight. So if you are going to use a multi-weight in OPE be sure it is a high quality oil.
 
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Originally Posted By: Chris142
My water cooled bikes oil gets that hot. I don't think that's too hot.


Hmm.....my 2000 Sportster 1200's oil temp runs around 200 degrees on a hot day. Hottest I have seen is 220.

Not sure what temp the oil runs in my mowers but if it makes a difference...which I figure it does.......I remove the hoods on the mowers when running them.
 
Originally Posted By: JimPghPA


Years ago I talked to a man who worked on out door power equipment for many years. He said that he had seen many engines that were damaged with multi-weight oils, and he strongly recommended mono weight 30 instead of multi-weight. So if you are going to use a multi-weight in OPE be sure it is a high quality oil.


Curious as I've heard that too. Did he say what happens? Owners manuals barely touch the subject other than 10w30/40 may cause increased oil consumption. Is it a case where someone puts in the oil, never checks or changes it and seizes it when it runs out? Or is it just not lubricating properly?

I know I use wheat ever leftovers I have in the OPE. I think it's got some 2003 vintage 1/2 bottle of Rotella in it now. Up next is some 2000 or so Mobil 1 5w30. I do check every time I start the OPE and change at the beginning of the season.
 
3100 is used as spec by some mowers. I don't recall for certain but I think my ZTR with one-lung 14hp briggs also governs for 3100. I could be wrong on mine, but I have seen it before when I was looking at riders.

The temps look fine. Wouldn't surprise me if it touches 250-260 when it's hot. Cyl head temps can climb a good bit higher on air-cooled engines.

Nice to have installed that gauge. Good mod!
 
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