Rather than looking at "two points" (not really, but you might get my point), look at the vis v. temp curves of the two or more oils.
Clearing up common misconceptions with Oil weights
- Thread starter Decreppo
- Start date
My (mystery car/truck) engine oil temp reports a couple degrees under 200f regardless of ambient - with a modest load. Been looking at the DICreadout in ambient temps of high 60's to over 100F. (DIC values verified with OBDii scantool - but not physical external probes)
Coolant temps were varying from 196 to 221.
After a cold start, you will see slower oil warming as you approach sub freezing temps and experience a lower average oil temperature due to the improved heat extraction from the external (pan) sump and lower block area - again with modest loading.
Where requirements can change is when you are pressing the engine to develop high torque and horsepower over an extended period of time. Like mountainous hauling or motorsports competition. This heats the oil from piston underside and cylinder head exhaust runners (under the valve cover oil runoff) and also higher oil mechanical shear rates from the crank journal spillage and oil pumping.
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So, on your point 1, absolutely no need to increase a grade** in summer months due to ambient - if the vehicle is operated moderately.
Towing, or heavily laden dipping heavily in the throttle for extended period where high oil temps are experienced you may wish to spec an oil with higher HTHS or KV 100 to maintain hydrodynamic /safe operation with infrequent forays into boundary regime (see R. Stribeck)
Adequate oil pressure is not enough here - exposing another automotive myth.
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** Specification: IlSAC GF-6A/B- Resource Conserving Lubricants
Coolant temps were varying from 196 to 221.
After a cold start, you will see slower oil warming as you approach sub freezing temps and experience a lower average oil temperature due to the improved heat extraction from the external (pan) sump and lower block area - again with modest loading.
Where requirements can change is when you are pressing the engine to develop high torque and horsepower over an extended period of time. Like mountainous hauling or motorsports competition. This heats the oil from piston underside and cylinder head exhaust runners (under the valve cover oil runoff) and also higher oil mechanical shear rates from the crank journal spillage and oil pumping.
_____________________________________________________
So, on your point 1, absolutely no need to increase a grade** in summer months due to ambient - if the vehicle is operated moderately.
Towing, or heavily laden dipping heavily in the throttle for extended period where high oil temps are experienced you may wish to spec an oil with higher HTHS or KV 100 to maintain hydrodynamic /safe operation with infrequent forays into boundary regime (see R. Stribeck)
Adequate oil pressure is not enough here - exposing another automotive myth.
___________________________________________________
** Specification: IlSAC GF-6A/B- Resource Conserving Lubricants
Based on what I have learned here so far, you can typically go to the next higher grade without doing any harm to your engine. By doing so, you get better wear protection than you would get with a lower viscosity. Do you need better wear protection? Here's some great info (you've probably already seen or may already be familiar with); skip to the 17:30 mark, and when done with that, skip to the 20:52 mark.
You can go to any SAE grade you want without harm as long as the winter rating is appropriate for your starting temperature.
70 grade oils are used in Australia in vehicles for which we have much thinner recommendations.
You could do a lot worse than just taking the following general practice:
- Start with the viscosity on the oil fill cap as a reference, go up one one hot grade (i.e. 20 grade to 30 grade). This is fine year round all the time.
- Select the cold (w-grade) needed for your location applicable time period. This could be anything from 0w to 20w depending on where you live.
There are non-viscometric reasons to prefer 0w grades now (better base oils), but that's a separate consideration from viscosity per se. This is why many respected members here prefer the 0w grades to get better bases, even though they live in areas where there's no need for the higher viscosity index based on winter temps.
It's worth reminding ourselves that higher VI doesn't *just* mean thickening less with cold, it also means thinning less when hot, and that's almost never a bad thing either.
- Start with the viscosity on the oil fill cap as a reference, go up one one hot grade (i.e. 20 grade to 30 grade). This is fine year round all the time.
- Select the cold (w-grade) needed for your location applicable time period. This could be anything from 0w to 20w depending on where you live.
There are non-viscometric reasons to prefer 0w grades now (better base oils), but that's a separate consideration from viscosity per se. This is why many respected members here prefer the 0w grades to get better bases, even though they live in areas where there's no need for the higher viscosity index based on winter temps.
It's worth reminding ourselves that higher VI doesn't *just* mean thickening less with cold, it also means thinning less when hot, and that's almost never a bad thing either.
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Given that it very rarely drops below +20 deg F where I live, I would be fine switching from the recommended 0W20 to 5W30. I'd get better wear protection and still be good on cold weather starts, while any loss in power of fuel economy would be insignificant.
It's cold here, gets to -60* most winters. 0w isn't that common to sell. One customer runs 0w30 Delo, another 0w40 Penzzoil (fleet if Dodge trucks)
Little but of 0w20 for Chevs.
Otherwise most else use 5w, or even 10w.
The diesels, 15w40 is the main one. I'd imagine more due to cost over 5w40 though. It's roughly $6a gallon difference and we're talking shops that use 300+ gallons a week.
And here's that distrust and conspiratorial thinking I talked about.
Patman
Staff member
I can’t even imagine how hard it is to start in -60 temperatures with anything higher than a 0w oil
I can’t even imagine how hard it is to start in -60 temperatures with anything higher than a 0w oil
It has to be heated. Either block heater or stick a heater under for a few hours.
Patman
Staff member
When I bought my first brand new car at age 18, it had a block heater as standard (which most Canadian cars did back then actually) I ran 10w-30 in that car (1988 Dodge Shadow ES Turbo) and even though I parked it in my warm garage I always used the block heater. Even though the temperature inside that garage probably never went below 50F, I felt that it was beneficial to have my coolant warmed up a bit for the cold starts. Even at 18 years old I knew that the most engine wear occurs in the time period between a cold start and when the engine is up to temperature.
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