I apparently don't understand oil weights

[LouNY]

Every manufacture has a different suggested oil weight for different temperatures,
that particular manufacturer in that specific application decided that 5w-30 would not be the recommended oil for operation
in temperatures above 50F.
Your specfic application from your particular manufacture desires a synthetic 5W-30 for all temperatures.

 

[deezler]

Another thing to keep in mind might be the quality of residual oil film for "cold" starting.

The last number on a multigrade oil is the HOT rating, at 100C. But on a hot summer day you are still only starting the engine at 30 or 40C max. A 5w30 oil is still thinner than a 10w30 oil at 40C - they really only converge to the same 30W rating at truly hot temps (100C).

Tried to find a good image to represent what I am saying, but it was surprisingly difficult.

 

[LouNY]

It has always amazed me how similar the viscosity of gear lube and motor oil are,
that a 75W-90 gear lube isn't really much heavier then a 10W-30 motor oil,
untill you get to higher temps then the motor oil is actually more viscous.

 

[RalphVa]

This is from my generator Install (left) and Operator's (right) manuals. If 5W30 is supposedly only good below 50F, why are they spec'ing it for all temperature ranges?

Also note, they supply 'organic' oil, but recommend synthetic.

View attachment 689323

5w30 is good for the 212 F it sees against your thermostatically control cooling water typically at 190 F.

 

[RalphVa]

Another thing to keep in mind might be the quality of residual oil film for "cold" starting.

The last number on a multigrade oil is the HOT rating, at 100C. But on a hot summer day you are still only starting the engine at 30 or 40C max. A 5w30 oil is still thinner than a 10w30 oil at 40C - they really only converge to the same 30W rating at truly hot temps (100C).

Tried to find a good image to represent what I am saying, but it was surprisingly difficult.

The plots are a straight line when fitted against log of viscosity vs. 1/T. Here's a graph of the crankcase and transmission/diff oil ranges. The transmission/diff oils are just rated at 40 C vs. 100 C for engine oils.

 

[grsthegreat]

This is from my generator Install (left) and Operator's (right) manuals. If 5W30 is supposedly only good below 50F, why are they spec'ing it for all temperature ranges?

Also note, they supply 'organic' oil, but recommend synthetic.

View attachment 689323

they want engine to break in with non-synthetic oils is the only reason. they recommend swapping to synthetic after 25 run hours.

 

[bcp]

I worked for over 3 years in the 1960's as a petroleum lab technician, and this thread really shows how much I've forgotten. Or how much things have changed.

Bruce

 

[Username Taken]

Bob Is The Oil Guy

Bob Is The Oil Guy

bobistheoilguy.com

 

[Sberry]

It isn't the hot rating. It's the cold so to speak. If the ambient is below the hi number they suggest a lower weight oil. Got nothing to do with it's hot performance. They are saying when the ambient is cooler use lighter. It's still about cold starts.

 

[RalphVa]

It isn't the hot rating. It's the cold so to speak. If the ambient is below the hi number they suggest a lower weight oil. Got nothing to do with it's hot performance. They are saying when the ambient is cooler use lighter. It's still about cold starts.

That makes sense. I tried to find someone to talk to who made those charts and could not find out how.

 

[Username Taken]

That makes sense. <snip>

But it is completely wrong

 

[RalphVa]

Well, the upper outside temps on the charts do not make sense otherwise, unless they're for air cooled engines. All oils in water cooled engines run at around 212-230 F, being cooled by coolant at 190 F thermostat setting. VW TDIs, millions of them, run around with 5w30 in their crankcases. None have ever had an engine failure due to oil, according to VW.

 

[Sberry]

How would the oil know how warm it is outside once its running?

 

[Sberry]

If 5W30 is supposedly only good below 50F, why are they spec'ing it for all temperature ranges?
It isnt "only" good there,,,, they just reccomend the 5 for lower temps.

 

[Sberry]

Bout like 110 and 220 volts.

 

[Sberry]

Gotta love the guys on Bob,,,fussing over their 5K changes endlessly and telling everyone how they should really sample to get at the truth,,,, then a guy pulls it at 41K and its still 50% and he is going to hell for sure. More living proof we can "research" more and know less.
I have seen a lot, a lot of stuff stops equipment, wears it out over long times. Its really people more than machines. Changing the engine oil can be a good thing but its not the only thing. Rear lube and keeping the vent open pays off, doesnt have to be like a bat out of hell but a freshen with new fluid about 1/2 way thru doesnt hurt. I know people obsess about having an oil change,,, break out in a sweat at 3500 miles but can somehow drive a car till the fins on a rotor are thru and blows out a caliper,,,, but,,,, I cant understand it,,, I have the oil changed all the time. Try splainin how they noit directly related and skipping a change wont hurt but wearing the pads thru just cost 500$,,, but get those deer in the headlights look,,, well I wouldnt want to have to replace the engine so I change the oil every 3K and simply dont see how the wheel fell off,,,, after all I change the oil regular,,, I am a firm believer in that.
19.95 oil special and all of a sudden an expert in car maintenance.

 

[Username Taken]

How would the oil know how warm it is outside once its running?

Most engine wear (about 90%) happens at cold starts.

Once an engine is running it depends on how it's being used. Severe duty can break oil down. Heat breaks oil down.

In a diesel, as longs it's in good shape, run 5w-40 synthetic and just drive it.

 

[LouNY]

^^^^^^ Too simple

 

[RalphVa]

Most engine wear (about 90%) happens at cold starts.

Once an engine is running it depends on how it's being used. Severe duty can break oil down. Heat breaks oil down.

In a diesel, as longs it's in good shape, run 5w-40 synthetic and just drive it.

Exactly. That's why it's very important to get a small "x" # in a xw30 or xw40. A tad fuel credit for xw30 vs. xw40, but it's on the order of 1-2%. Main thing is to get a small first # which allows the oil pump to "grab" the oil instantaneously vs. sitting there "warming" the oil by not pumping it for a few seconds, with your bearings and upper valve train starving for pressure lubrication.

A synthetic will stand severe duty and heat a lot better because it has a higher boiling point for a given grade of oil.

 

[Sberry]

Read Bob for 5 minutes, pull 5K sample and become expert.