Oil - Another "why" question

[Beltzington]

I have read literally hundreds of articles and reviews on oils and still can't seem to get my brain around the logic of using a heavy weight oil for hotter outside air temps. Why would you use 10w-30 for -20F thru 100F and 15w-40 for -10F thru 120F? I understand the lower cold startup winter weight however the operating weight makes no sense to me as the engine operating temp is well over the outside temp once the engine warms up to, let's say, 180F for discussion. If 10w-30 is ok for a warm engine why recommend 15w-40? My guess is it was nothing to do with outside air temperature and more do with them hedging against the quality of chemicals used to modify the viscosity to increase the span between winter and operating weights. SO, based on this assumption my take-away is if you always use a high quality oil "Brand X" than 5w-40 is the best choice for all situations.

Anyone see this differently?

 

[Oldpath05]

Heavy weight oil is recommended for tractors because it gives more ballast, keeping the front end down.

 

[dickfoster]

Heavy weight oil is recommended for tractors because it gives more ballast, keeping the front end down.

Is that to keep the front end down on your way to the snipe hunt?

 

[Oldpath05]

Is that to keep the front end down on your way to the snipe hunt?

Think you need to use synthetic oil for that.

 

[bdog]

I too wondered the same thing until I had a truck with a digital oil temp gauge. Your oil gets hotter than your coolant temp and your oil does in fact get hotter when it is hot outside than when it is cold.

I don't remember the exact numbers but on my diesel truck my oil was significantly cooler after several hours on the road in 30-40 degree temps than it is while driving in 100 degree weather. It wasn't 60-70 degrees warmer but more like 10-20 if I remember correctly. I can see at 100+ temps the oil being thinned out enough to necessitate the 15-40 vs 10-30.

 

[namesray]

I have read literally hundreds of articles and reviews on oils and still can't seem to get my brain around the logic of using a heavy weight oil for hotter outside air temps. Why would you use 10w-30 for -20F thru 100F and 15w-40 for -10F thru 120F? I understand the lower cold startup winter weight however the operating weight makes no sense to me as the engine operating temp is well over the outside temp once the engine warms up to, let's say, 180F for discussion. If 10w-30 is ok for a warm engine why recommend 15w-40? My guess is it was nothing to do with outside air temperature and more do with them hedging against the quality of cstophemicals used to modify the viscosity to increase the span between winter and operating weights. SO, based on this assumption my take-away is if you always use a high quality oil "Brand X" than 5w-40 is the best choice for all situations.

Anyone see this differently?

This seems like a interesting topic to me. Good question. Your theory makes sence. With 5w 40 you get the best of all the operating conditions and ranges. I too ask a lot of questions about oils. I have asked on tbn here, mechanics where I work, equipment dealers, even kubota corporate. I never get a in depth detailed answer.

I can tell you this. I work for the state highway dept. I have been told (and believe) by the mechanics that ALL equipment and vehicles get the same oil, 15w 40 diesel oil. This means the big trucks, loaders, exevators, graders, down to the gas engine pick up trucks and cars stating 5w 20 oil, and even the lawn mowers and push mowers stating 30 weight oil. The bigger equipment of course. The pickups and cars all last over 100,000 miles with never an engine failure. And the lawn mowers through out the years always work too. This all happens in the northern Pennsylvania climate, both summer and winter.

The only issue I have ever heard they had was with the new tier 4 engines in the big equipment/trucks. They were using the older class of engine oil with higher ash contnt and it was clogging the regen dpfs quicker then should have.

So I am thinking it is all a hoax. As long as it has oil, it'll work better then no oil! So my search for more info on oil types goes on. I am contemplating if it would be ok to switch from kubota oil to shell rotella t oil for my tier 4 tractor engine. Save about $10 per gallon.

 

[3930dave]

I have read literally hundreds of articles and reviews on oils and still can't seem to get my brain around the logic of using a heavy weight oil for hotter outside air temps. Why would you use 10w-30 for -20F thru 100F and 15w-40 for -10F thru 120F? I understand the lower cold startup winter weight however the operating weight makes no sense to me as the engine operating temp is well over the outside temp once the engine warms up to, let's say, 180F for discussion. If 10w-30 is ok for a warm engine why recommend 15w-40? My guess is it was nothing to do with outside air temperature and more do with them hedging against the quality of chemicals used to modify the viscosity to increase the span between winter and operating weights. SO, based on this assumption my take-away is if you always use a high quality oil "Brand X" than 5w-40 is the best choice for all situations.

Anyone see this differently?

Up until not that long ago, most charts like you posted were created with conventional oil in mind - vehicle manufacturers knew that many consumers did not want to be forced into buying synthetic oil.

The xW40 option on the old charts was to give people hauling heavy in extreme heat a way to minimize oil consumption. Modern synthetics have low volatility at high temperature, but the easiest way to reduce consumption with older conventional oil was to bump up the viscosity.

A good quality modern 5w40 is a versatile oil, that will cover many applications.

Rgds, D.

 

[KubotaToy]

The same as namesray stated about the highway department, my father has used bulk 15w40 on the farm from the cheapest wholeseller he could find since 1974. 15w40 was used in every tractor, truck, utility vehicle on the farm, never experienced a problem. I used 5w40 in all my equipment and will in my truck when the warranty ends. Bottom line, use whatever oil that makes you feel good but keep oil in it and change it on a reasonable basis.

 

[Beltzington]

Thanks for the comments, I always go through this every time I due my annual service on the tractor. I think I may have asked my question poorly, so let me try again.

If I know I will never be operating below 0F or above 105F is there a best weight oil? Synthetic 5-40, 10-30, or Dino 15-40. Or should I just stop worrying about this and start thinking about problems I can solve like global warming

 

[Oldpath05]

"(Or should I just stop worrying about this and start thinking about problems I can solve like global warming)"<<<Yes exactly, get rid of your diesel guzzling tractor and switch over to a battery powered tractor and we can all live in harmony, sit around the battery powered camp fire and sing Kumbaya, no more worrying the brain numbing kunfusing motor oil numbers and diesel fuel color., I'll be behind you all the way..............

 

[RjCorazza]

In my area I may see single digit temps and have to use the tractor. My previous L3410 got 5w30 for 15 years. I decided on 5w40 for the new L4060 because my preferred oil brand does not offer a CJ4 spec oil in 5w30. Any of the weights you list will be fine, just make sure the oil meets whatever specs your tractor and emissions systems require.

 

[Beltzington]

"(Or should I just stop worrying about this and start thinking about problems I can solve like global warming)"<<<Yes exactly, get rid of your diesel guzzling tractor and switch over to a battery powered tractor and we can all live in harmony, sit around the battery powered camp fire and sing Kumbaya, no more worrying the brain numbing kunfusing motor oil numbers and diesel fuel color., I'll behind you all the way..............

My Deere runs forever on a few drops of diesel, maybe time to upgrade. Sorry for your pain.

 

[Oldpath05]

Sorry for what pain. pain in back, pain in the foot, or pain in the neck, some people have no sense of hummor:thumbdown:

 

[Copperhead]

While true, a 5w40 will give you the best of all operating temp conditions, it is also less shear stable than a 10w30 or 15w40. It requires more viscosity improvers, which can shear under extreme pressure. It is a balancing act. Yes, even a PAO synthetic 5w40 requires some viscosity improvers. Now it is true, there are some PAO 10w30 oils that don't require viscosity improvers.

I have been using a 10w30 syn blend in my commercial semi truck for quite a while. Better used oil samples than I got with a 15w40 in the same motor. 540,000 miles on it now, and it is a factory reman motor. Mater of fact, the same 10w30 HDEO CJ-4 / SM syn blend that goes into my Detroit 12.7L motor is also the same oil I use for almost everything else i own from portable generators right on up thru my CUT. Winter, Summer, it doesn't matter.

One has to factor hydrodynamic and boundary lubrication, shear stability, along with characteristics of the add pack component formulation in all this. Weight alone does not give the complete picture. Both synthetic 10w30 and blend 10w30 oils have cold flow pour points that are within a few degrees of any 5w40. Unless one is in the interior of Alaska or the harsher Canadian provinces, (or a special application engine), a 10w30 will fill the need of just about anyone. I run my semi thru the Dakotas, MN, Wisc, Mich, just about all the midwest all winter long on a 10w30 (and I shut the motor off at night when I stop for a break). Same oil gets used to pull the same loads in 100F ambient temps also. The engine uses about 2-3 qt in 22,000 miles. It holds 40 qt. Not bad for a 2000 factory reman motor with over half million miles on it after the reman.

 

[DEWFPO]

I once had a car with twin turbos and a small 6 cylinder gasoline engine with a manual transmission. It also had an oil temperature gauge on the dashboard. On long hard pulls up over the continental divide in Colorado the engine oil temp would hit 250F even when coolant temps were at 195. The owner's manual said that when engine oil temps hit 250F you should get your foot out of the turbos to allow it to cool down, which it would do fairly quickly. The oil spec'd for that engine was dino 5w30. The oil was always black even within a few days of an oil change. That was 13 years ago. I was surprised the manufacturer (AUDI) didn't spec synthetic oil for this application.

DEWFPO

 

[CurlyDave]

Thanks for the comments, I always go through this every time I due my annual service on the tractor. I think I may have asked my question poorly, so let me try again.

If I know I will never be operating below 0F or above 105F is there a best weight oil? Synthetic 5-40, 10-30, or Dino 15-40. Or should I just stop worrying about this and start thinking about problems I can solve like global warming

There is an answer, and it is very complicated. Way back when, from '67-'72, I was in graduate school and my thesis advisor was a rheologist (a guy who studies flow of fluids). Oil is not a simple fluid, and the viscosity enhancers they add have some very unexpected effects. One of these is called the Weisenberg effect. If you do the math, and believe me, it makes calculus look like a Sunday school picnic, there is a force which tends to center a shaft in a journal bearing caused by the viscosity enhancer. This obviously reduces wear.

Bottom line: the wider the range of viscosity the higher this force is. Other things being equal 5W-30 is better than 10W-30.

 

[dragoneggs]

There is an answer, and it is very complicated. Way back when, from '67-'72, I was in graduate school and my thesis advisor was a rheologist (a guy who studies flow of fluids). Oil is not a simple fluid, and the viscosity enhancers they add have some very unexpected effects. One of these is called the Weisenberg effect. If you do the math, and believe me, it makes calculus look like a Sunday school picnic, there is a force which tends to center a shaft in a journal bearing caused by the viscosity enhancer. This obviously reduces wear.

Bottom line: the wider the range of viscosity the higher this force is. Other things being equal 5W-30 is better than 10W-30.

Curly, thanks for taking me back to my fluid dynamics classes and the reason I drank a lot of beer in college. Not sure which was worse the hangover or the math headache. :laughing:

 

[bdog]

Thanks for the comments, I always go through this every time I due my annual service on the tractor. I think I may have asked my question poorly, so let me try again.

If I know I will never be operating below 0F or above 105F is there a best weight oil? Synthetic 5-40, 10-30, or Dino 15-40. Or should I just stop worrying about this and start thinking about problems I can solve like global warming

In those conditions any of the three would work fine. The 5w40 would technically be the best but it certainly isn't necessary and the others would be fine. If I were making the choice I would look at the temps you will operate in. You said you won't be out of the 0-105 window but which end are you likely to be closer to? If the cold end go 10w30 if the high end 15w40. Being you are in Georgia I would think probably the 15w40. I live in Texas and I buy 15w40 by the drums.

 

[RalphVa]

Use a good 5w40 oil to fill in all temps on that chart of yours. Think synthetics have little to no VI additive to do this.

You want the low 1st # to get oil to the top end on startups. That's when most wear occurs. A 15w oil will take a second or so longer to get up there, vs. a 5w or 0w oil.

Ralph

 

[Beltzington]

Bottom line: the wider the range of viscosity the higher this force is. Other things being equal 5W-30 is better than 10W-30.

This horse may still be alive so let me kick it a few more times. I'll differ the math to better minds, I always did well in college but I had to work hard at it. Based on your summary I'm curious if 5w-30 is better than 10w-30, wouldn't 5w-40 be even better? Specifically I am wonder if 40 weight is just to heavy for my operating envelope. Although anecdotal evidence seems to indicate otherwise.

Thanks folks.