Engine oil substitute (5W-20 or straight SAE-20)

pwyld · Jun 9, 2016

My tractor manual (IH 300U) recommends straight SAE 20 oil for my engine cranckcase. I can find SAE 30, but finding it a little difficult to find straight SAE-20.

My question is can one use 5W-20 weight auto oil as a substitute? My understanding is the 5W is for cold starting in the winter, but when the engine gets hotter the viscosity will become a 20 weight at operating temperature.

I understand that automotive oil will have additives in it, but would this really be harmful to a gasoline tractor eingine or would it be better?

Any thoughts out there?

chuck2015 · Jun 9, 2016

(quoted from post at 05:04:00 06/09/16) My tractor manual (IH 300U) recommends straight SAE 20 oil for my engine cranckcase. I can find SAE 30, but finding it a little difficult to find straight SAE-20.

My question is can one use 5W-20 weight auto oil as a substitute? My understanding is the 5W is for cold starting in the winter, but when the engine gets hotter the viscosity will become a 20 weight at operating temperature.

I understand that automotive oil will have additives in it, but would this really be harmful to a gasoline tractor eingine or would it be better?

Any thoughts out there?

Just run the 30 weight oil?

gene bender · Jun 9, 2016

Any grade oil will be just fine like 10-30 ect car engines are gas so is the tractor use it and go for it

jimg.allentown · Jun 9, 2016

My understanding (not necessarily correct) of oil viscosity is that the first number is the actual viscosity of the oil at ambient temperatures. The second number is the viscosity at operating temperatures.
So, to me, a 5W-20 oil is basically a 5 weight oil that doesn't thin out as much as a straight 5 weight oil would. I'm sure one of the oil experts here will correct me on this.

What I will say about this is that I would hesitate to use modern low viscosity oils in older engines. Most modern automotive engines are using more tightly controlled clearances along with some VERY sensitive mechanical devices - like hydraulic tensioners on timing chains and variable valve timing. As such, they have a whole new set of requirements for lubricants. An older tractor engine might have larger clearances and altogether different lubricant needs.

I would think that your safest option would be to use the straight 30 weight. Might crank a bit harder, but otherwise just a bit heavier oil.

T in NE · Jun 9, 2016

I'd just run 10- or 15-40 in it.
The book doesn't call for a multi-grade because they
didn't exist back then.

If it gets really hot in summer and you're working
it hard, maybe 20-50 in summer.

dpendzic · Jun 9, 2016

it has been my understanding that oils of years ago used a different set of parameters to determine viscosity so they were thicker than modern day oils of the same rating---I would think the straight 30W would be just fine.

dhermesc · Jun 9, 2016

Correct. 10W30 at operating temp has the same viscosity as 30W at operating temp (about 210 degrees) - when "fresh". After 100 hours of use though the 10W30 MIGHT (probably) have less viscosity than straight 30W after the same amount of use. The bigger the multiple between the "W" number and the last number the more likely the oil will break down - especially in conventional oils. 5W40 has a multiple of 8 - not nearly as stable as 15W40 (multiple of 2.67) (usually). 10W30 has a multiple of 3 and 5W30 has a multiple of 6 - the 10W30 is less likely to lose viscosity (use will lose less viscosity) than the 5W30 (USUALLY).

A lot of this also has to do with the QUALITY of the motor oil. A good QUALITY 5W30 MIGHT be able to out perform "Casey's" 10W30 that's on the shelf in the C-Mart. In my opinion 10W30 Castrol GTX is one of the best conventional motor oils you can buy - while the next guy will tell me I don't know &^%$ and it is something else.

Grampy · Jun 9, 2016

I've shared the same concern about older engines, but after some study, I went to 15-40 in all of them at least 15 years ago. Have '0' problems with it. Where I formerly worked - a surface coal mine -- we phased out straight weight motor oil back in 1983. Even Detroit Diesel reluctantly gave up and said 15-40 was OK. Every gas engine on the place except pickups also went to 15-40. Never had a problem.

DeltaRed · Jun 9, 2016

Multiviscosity is perfectly adequet/acceptable for your tractor. Multivis did not exist when your tractor was built,Hence the
recomendation.Run 15/40 oil year around.I run 15/40 fleet diesl in all(10 runners) my
tractors,combines,trucks,pickups,motorcycles,ATV,lawnmowers....... for 40 years and have never had a failure.One oil for all.
Simple and no confusion or 'mix ups'.

David G · Jun 9, 2016

I think 5W is too thin, I run 15W-40 in everything.

old · Jun 9, 2016

A whole lot depends on where you are located. If you say in Alaska your would want something like a 5W30 or even a lower first number if they make it. But if you in say New Mexico where it get real hot you might want a 20W-50 like I use here in Missouri. But you have to remember back when that tractor was made the oils of the time where not near as good as they are now

rustred · Jun 9, 2016

well any oil is better than what the manual is saying, as its outdated.depending on weather just use 10-30 , 10-40 , or 20-50 . the 15-40 is the diesel oil and that is ok too. 20w is so obsolete.
its the old detroit diesels or " jimmy's " that require the straight 30 weight oil.

MarkB_MI · Jun 9, 2016

10W-30 north of the Mason-Dixie line, 15W-40 south.

Brent Zappe · Jun 9, 2016

many years ago when I was in Automotive schools they would talk about engine oil. back in the late 79's they had told us that the oil could only be guarantee for the lowest wait it said. As engines started to get more stuff like turbo and super chargers which requires the four cylinder to have (a high torque) requirs a muliti grade. the oil starts as a 5 wait when engine is cold but as it warms up it will thickend to a 20 wait. this will give you the protectiion of a 20 wait.when it is required for this engine to have. the problem is that today engines require a mulity wait oil not just one wait.

buickanddeere · Jun 9, 2016

(quoted from post at 08:04:00 06/09/16) My tractor manual (IH 300U) recommends straight SAE 20 oil for my engine cranckcase. I can find SAE 30, but finding it a little difficult to find straight SAE-20.

My question is can one use 5W-20 weight auto oil as a substitute? My understanding is the 5W is for cold starting in the winter, but when the engine gets hotter the viscosity will become a 20 weight at operating temperature.

I understand that automotive oil will have additives in it, but would this really be harmful to a gasoline tractor eingine or would it be better?

Any thoughts out there?

No Shell oil dealers in the area ?

buickanddeere · Jun 9, 2016

(quoted from post at 12:42:29 06/09/16)

(quoted from post at 08:04:00 06/09/16) My tractor manual (IH 300U) recommends straight SAE 20 oil for my engine cranckcase. I can find SAE 30, but finding it a little difficult to find straight SAE-20.

My question is can one use 5W-20 weight auto oil as a substitute? My understanding is the 5W is for cold starting in the winter, but when the engine gets hotter the viscosity will become a 20 weight at operating temperature.

I understand that automotive oil will have additives in it, but would this really be harmful to a gasoline tractor eingine or would it be better?

Any thoughts out there?

Click to expand...

No Shell oil dealers in the area ?

Much to my surprise Shell has dropped the 20 weight ? Some 10W-20 something will do.http://rotella.shell.com/products/t1.html

farmall300u · Jun 9, 2016

I have a 300U and I run Rotella 15W40 diesel oil in it for 10 years, engine is great. I tried 5W-30 2 years ago as it was on sale, used 2 qts every 5 hours running bush hog in tall weeds. Switched back, no oil usage.

jm. · Jun 9, 2016

My thoughts on that 40 year old unit is use the 15/W40 or 30 wt . Twenty weight is just too thin for that worn engine.. Just my experience

CenTex Farmall · Jun 9, 2016

This is true.

10W-30 is 10 weight oil that when warm exhibits properties of 30 weight. The viscosity modifiers are straight when cold and coil up like spaghetti when warm. (rough analogy)

CenTex Farmall · Jun 9, 2016

Bingo!

Mixed fleet oil for the win.

Janicholson · Jun 9, 2016

With Respect, The oil at freezing temps does not get thicker than a 5 wt. and at operating temps it doesn't thin down more than a 30 wt. It never thickens when hot, nor thins when cold. It is just staying closer to the same viscosity through the temperature swings. API based info. Jim

jacks · Jun 9, 2016

Centex, I agree with your reply, except I think that the second part is reversed. Almost all multi weight oils have a base viscosity of the lower number. They use viscosity modifiers to make the oil function with different effective viscosity especially at different temperatures. The viscosity modifiers are long chain molecules which coil up at lower temperatures and the oil functions at its unmodified viscosity. The coiled up molecules bounce around like tiny balls, which have no effect on viscosity. At higher temperatures the long chain molecules unfurl, increasing the effective viscosity. When the long chain molecules are unfurled, they are vulnerable to shear stress, and they gradually get cut into shorter and shorter lengths. The higher number of the viscosity range gradually reduces, and the oil thins at high temperatures. Small air cooled engines seem to have the oil operating at a higher temperature than most liquid cooled engines. Over on the "Bob is the oil guy" forum, someone measured a temperature of 275 degree F on his air cooled lawn tractor oil filter during mid summer use. This kind of temperature can degrade the viscosity improver molecules and shear them quickly, and I think it explains why many small engine manufacturers maintain their straight 30 weight oil requirement for summer use. I use Rotella 15-40 in all my diesel engines, and straight 30 wt in all air cooled gas engines.

jacks · Jun 9, 2016

Centex, I agree with your reply, except I think that the second part is reversed. Almost all multi weight oils have a base viscosity of the lower number. They use viscosity modifiers to make the oil function with different effective viscosity especially at different temperatures. The viscosity modifiers are long chain molecules which coil up at lower temperatures and the oil functions at its unmodified viscosity. The coiled up molecules bounce around like tiny balls, which have no effect on viscosity. At higher temperatures the long chain molecules unfurl, increasing the effective viscosity. When the long chain molecules are unfurled, they are vulnerable to shear stress, and they gradually get cut into shorter and shorter lengths. The higher number of the viscosity range gradually reduces, and the oil thins at high temperatures. Small air cooled engines seem to have the oil operating at a higher temperature than most liquid cooled engines. Over on the "Bob is the oil guy" forum, someone measured a temperature of 275 degree F on his air cooled lawn tractor oil filter during mid summer use. This kind of temperature can degrade the viscosity improver molecules and shear them quickly, and I think it explains why many small engine manufacturers maintain their straight 30 weight oil requirement for summer use. I use Rotella 15-4 all my diesel engines, and straight 30 wt in all air cooled gas engines.

CenTex Farmall · Jun 10, 2016

Good catch!

On second thought I DID goober up the explanation. As you said, the chains uncoil and get long and tangled.

I haven't been on BITOG in a while. Tons of information over there.

I can't disagree with the logic of using a straight weight for a high stress situation.

Years ago I remember at the flight school they ran, I believe, 20w-50 in the school's aircraft. There was always unequal heating between the front and the back cylinders but overall I believe they ran cooler than optimum. It was not uncommon to find slimy mess from condensation in the rocker boxes. I don't remember any of them having oil temp gauges but for a while they had a couple of Mooneys that may have had them. It's been too long for me to remember for sure. They did have six cylinder engines with a hotter tune and the cooling inlets were fairly small. They would overheat on the ground on a hot Texas day and you had to pay attention to that.

BarnyardEngineering · Jun 10, 2016

As I recall, manuals from that era had a chart which told you what weight oil to use in what temperature. There wasn't a single weight oil recommendation.

SAE-30 is fine to use in summer months.

Alan K · Jun 10, 2016

There are places that sell 20w yet. I agree that might be thin for an old engine. We
have always used 30w in the summer and 10w-30 in winter months.

Engine oil substitute (5W-20 or straight SAE-20)

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