Which transfers heat better, thick or thin oil?

[James408]

I am somewhat confused on this topic. I have read, I think on this sight that the thicker the oil, the higher your oil temp will be.

I have read elsewhere that thicker oil will will keep your engine cooler vs. a thinner oil. What is the truth?

 

[medic]

This was recently discussed in another post. The are multiple opinions there, but the general thought is that most oils absorb heat at the same rate, just some move through the engine quicker.

Check this thread: web page

 

[MolaKule]

Generally speaking, the denser and thicker the oil the more heat it can abosorb, but it takes a longer time to absorb the heat.

A thinner oil, while having a slightly lower heat capacity, actually transfers heat quicker because it moves faster.

The real trick is to move the oil fast and cool it as soon as possible.

 

[1sttruck]

Most 'heat transfer oils' seem to be thin. Better heat transfer is similar to tracers in ammo, in that tracers 'work both ways'. A thin oil flowing more freely thru a cold engine will also cool the oil more.

 

[toolboy62]

I don't have any gauge data to back this up but I can tell you this, I've been running 15W50 Mobil 1 in my Porsche 944. Just last week I started a new job which involved a truly grueling commute around the DC beltway. After sitting in stop and go traffic for a while in 90 degree heat I was getting serious detonation while trying to accelerate. I blamed it on Shell gas (I usually run Chevron with no problems but anymore I don't regularly drive by a Chevron station so I have to take what I can get.)

I changed my oil to Mobil 1 0W40 over the weekend. Not only does my car feel much better, but oil pressure has dropped only marginally, and guess what - despite being stuck in miserable traffic trying to get home from work today, ZERO detonation. Now it was only 80 degrees not 90 today, but still... I have to wonder if the oil didn't have something to do with it. I didn't fill up my gas tank until I was almost home, so the fuel in the tank was the same as that I was running the latter part of last week.

nate

 

[1sttruck]

AeHaas (speling) provided some data that showed that a fairly heavy oil (50W as I recall) in one car resulted in high oil temps, a thin oil slighlty less, an an oil just right resulted in the lowest temps.

 

[Doug Hillary]

Hi,
toolboy62 - the oil temperatures in coolant cooled Porsche engines (especially 944/928) is very well controlled. It usually runs at between 85c and 95C (core temp 91-93C)

A heavier than specified oil in Porsche engines does have some consequences - M1 5w-50 is Listed and M1 15w-50 isn't

Your oil pressure gauge will be more "alive" with the correct grade of oil. Next oil change you may also consider M1 5w-40 T&SUV but M1 0w-40 will do the job well

Did M1 15w-50 cause your detonation? It is unlikely but these engines do breath strangely and oil volatility and foaming play a major role in Porsche's oil Approval protocols

Regards
Doug