Correct Viscosities Vs Ambient Temperatures

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6
Location
kryp
I live in JHB, temperatures here in winter go down to 5 in early mornings but warm up to average of 15-20degrees C. Summer it averages from 15-20 in the mornings and gets sometimes hot maybe 25-35 degrees C. I'm fully aware of thinner oils are far better,having better starting abilities and running smoother,with better fuel economy. [Wink] I'm currently running RL 5w40, its winter here, no problems but suggestions concerning viscosity ALL year round.... [Frown]
 
Messages
3,833
Location
NEPA
Ambient temps should not matter as far as viscosity for operating temps go. You must have a reliable oil temp guage to determine if your engine oil is running warmer in summer. Some cars experience no difference winter or summer, and changing visc would be pointless. Now, ambient temp does matter as far as starting visc goes and the "W" rating should be optimized for colder conditions. A low "W" rating in warm ambient temps is no problem.
 
Messages
1,294
Location
Western Washington
quote:
Ambient temps should not matter as far as viscosity for operating temps go.
Ambient temperature can have a big effect on operating viscosity. Naturally, the effect could be large or small depending on the car. For example, on a 70-90 degree summer day, my Accord will produce oil temperatures of 215°-230°. I've seen it get as high as 235° on a 100° day with lots of idling with the A/C on. On the other hand, If it's 50-60 degrees outside, I rarely see the oil temperature get above 205° or so. Lately, driving 65-70 mph on the freeway at night with air temperature in the 50's, my oil temperature doesn't break 195°. It's like I'm running a thick 40 weight/thin 50 weight oil, when the jug says 10W-30!
 
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2,435
Location
Mizzou-land
Palut, Where are you oil temps measured? In other words, where is the thermometer/thermocouple/sending unit physically located?
 
Messages
1,294
Location
Western Washington
quote:
Originally posted by GMorg: Palut, Where are you oil temps measured? In other words, where is the thermometer/thermocouple/sending unit physically located?
The oil temperature sender is in the drain plug. So it's sump temperature.
 
Messages
2,435
Location
Mizzou-land
I would guess that sump temp would be affected by ambient temp to a much, much greater degree than oil temps at lubricated surfaces. I would also suggest that oil temp on a cylinder wall during an exhaust stroke is affected very little by ambient temp (once engine is warmed to equilibrium). So, I agree with your position up to the point where the oil starts the transit through the engine.
 
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13,132
Location
By Detroit
Your lowest temp is 5C? Thats about 41F. You could run straight 30 weight in those temps. If you like to run Redline, I would go over to 10w40. I understand (somewhere it was posted on this site) that Redline has no VII except for the 5w40. I'm sure the RL 5w40 is fine, but you don't need a 5w by any means.
 

PLRR

Thread starter
Messages
6
Location
kryp
Its for a F355 Challenge Ferrari. Its essentially a race vehicle because its on the track only, but Shell recommends a 5w40 and there ain't no way i'm putting a GrIII oil in my car, oil temp's are high with Shell aswell, but it was recommended a 5w40 because the computers inside don't show high or low oil pressures with a 5w40. Suggestions
 
Messages
1,203
Location
Oregon
I agree with Palut from what I have seen with cars with oil temperature gauges. As far as oil temperature once its starts to transit through the engine. Its kind of hard to for me think that a oil being pressurized would get any cooler from what I have seen at work around pressurized Hydraulic and air systems. The harder the pumps work the more heat in the systems. Here is an interesting article I've posted before some might want to check out. Link to article
 
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