Oil brand/viscosity and coolent temp?

[Drew99GT]

I know they shouldn't be related, well, perhaps if you ran 20w-50 in a car requiring 5w-20. My car has electric cooling fans that don't turn on till 215 degrees. 5w-30 penzoil made my car run right at 200-205, even while idling in stop and go traffic. Whenever I switch to Castrol 10w-30, my car heats up faster, not oil temperature, but coolent temperature. Well, it seems any 10w-30! Cars and trucks with belt driven fans probably wouldn't notice a difference, but does anyone else notice a difference like this between different brands of oil or viscosities?

 

[Drew99GT]

I have no clue how I posted twice, but I apologize!

 

[Bill J.]

This past summer, I experienced this phenomenon right after I flushed the transmission with Amsoil synthetic ATF. I would pull off the highway (same 20+ mile trip, go into the same McD's drive up and the cooling fan would kick on about 15 seconds later. After the trans flush it would take about 3 minutes. I also noticed the A/C ran cooler and I could keep it at a lower fan speed.

I was running Mobil 1 10-30 then but I felt the 10-30 was not the right viscosity for the car, so now it is switched onto Mobil 1 0-40. I think the car likes this grade, we'll see what the analysis says. I have to wait until summer to duplicate the test with the 0-40.

 

[mdv]

quote:

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Originally posted by Drew99GT:
Whenever I switch to Castrol 10w-30, my car heats up faster, not oil temperature, but coolent temperature. Well, it seems any 10w-30! Cars and trucks with belt driven fans probably wouldn't notice a difference, but does anyone else notice a difference like this between different brands of oil or viscosities?

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If we're talking about initial warm up time and the same temperatures, using a 10W-30 over a 5W-30 would cause a difference in how well the oil flows when the engine is first started. Since 10W-30 shouldn't flow as well, the engine is going to have to work harder to move the same amount of oil through the system. This extra work should reduce the warm up time.

That's my thought anyway, though I think it would have to be fairly cold to see a major difference. The difference between the same weight of different brands can explained in a similar way.

 

[Drew99GT]

Maybe it is because of the warm up and it just carries on as the entire motor comes up to temperature. With the 5w-30, as soon as the thermostat would open, the temperature would drop dramatically, then level off at about 200 degrees, but now it just goes right up to about 205 and stays there. But when I hit a dirve thru like was posted above, it instantly shoots up to 215 until the fans turn on. Hmmmmm, maybe 5w-30 is what my engine likes? Especially in cold weather? I just wanted to try out 10w-30 instead of 5w-30 because of some of the issues mentioned on the site, and the coldest it's been getting here is about 10 degrees F.