As promised, here are the results of my expirement with oil weights versus engine run temperature. The temperature was SUPPOSED to be 80 here in Rhode Island today, but with the on-shore breeze it's barely over 70 (LOTS warmer today at the Boston Marathon!!)
Both of these test runs were made about 15 minutes apart between 1:30pm and 3pm today.
I started with Penzoil 10W-30 which had been run for about 1000 miles (the engine break-in period). Made a run to New Bedford (about 30 minutes round trip) on I-195. Kept the engine revs at 3500 the entire time (OK, so I "blipped" it a couple of times to pass people.....big deal).
Stopped right off the exit ramp in New Bedford, and read the temp from the dip-stick gauge and it was 222 degrees (F). Made the return trip on I-195 but kept the revs at 4,000 rpm and stopping right off the ramp showed a temp of 225 degrees (Which, I think, is where the thermostat is supposed to be holding the temp.)
Returned home, and changed the oil to 20W-50, then made an identical run as the first for speed. Stopped in New Bedford, and the temp was 198 degrees-F, after running at 3,500 rpm. Ran back to Fall River at 4,000 (blipped it around some old buck in a 996 Carerra - THAT was fun!), stopped and the temp was 220 degrees.
Interestingly, with either oil, once I got down under 3500 rpm the temp drops 7 - 10 degrees and stays there, but that was running south toward the shore on rt. 24 and the "shore cooling effect" is pretty dramatic today.
In summary: This was NOT a scientific performance, since the wind, outside temp and moisture in the air are all very variable around here right now. The outside temp in Fall River was about 73, while coming back to my house on the shore, about 7 miles away, drops the temp down to under 60 (!!) Ocean temps here are in the upper 40's F which has a great effect on everything close to the shore.
Anyway, I had heard that heavier weight oil could give as much as 20 degrees (F) difference, but I only saw a difference of about 5 degrees FOR THIS EXPIREMENT. Things may be different if this was a much hotter day as the oil should retain more viscosity, coat thicker and (hopefully) cool better.
Again, it would be cool if someone with an engine dyno could test a couple of different types of oil (as well as synthetics) for cooling performance, but that is beyond what I can do.
Gordon
PS: This was an interesting run: I saw a trailer with six (6) bare Cobra bodies heading East on I-195, saw that 996 Carerra going West, Was passed by a girl in a VW Golf Cabriolet that must have been going close to 100, and was beeped at, and waved to, someone that I used to work with ten years ago!! Speedsters seem to be magical!
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