[Shotimes] Re: synthetic oil and oil pressure and race fuel

[Leigh Smith]

You mentioned over 250F. I wonder how much over? If it only hit 260F why
worry about it?....
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I know you push your car prety hard, so this is unfortunately a little
long...
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I agree you'd like to keep the oil temp under 250F or so, but on the track
for long periods that just may not be possible without an aggressive cooler
setup. I used to have a 7500 rpm small block chevy with 411s and an oil temp
guage. Any extended cruise over 50 mph (3000 rpm) and the oil temp would
climb past 240F like 10F per 5-10mph. Piston speed friction and valve spring
pressure generate most of the oil heat. I've seen as high as 300F. My road
race open track time was oil temp limited before I added oil coolers. Chevys
racing recommendations are 150 to 270F at all times, with good oil pressure.
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Cold oil increases oil pressure, hot oil decreases it... Get it hot enough
and your idle oil pressure just about goes to zero! BTDT
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I would not eliminate the stock oil to water cooler. It actually performs 2
functions. It warms the oil with a cold motor more quickly to above 180F.
Cold engines are where most bearing damage / wear occurs. Also water cools
5-10 times as well as air. If you've ever added a trans cooler, they
recommend keeping the stock water based one and adding an air based one
downstream. Do the same for the oil. If you remove the stock one you could
easily be removing more heat capacity than you are adding.
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On the other hand, the water based cooler is never going to drop the oil
temp below 205F if the water temp is 190F. You could run the oil as cold as
180F but it should stay below 250-260F for longevity.  If you rig up an
external oil filter, you'll have a hot oil hose that you could run thru an
external air to oil cooler. I suspect the factory oil flow is filter first,
cooler second. That would mean your new air cooler would take the edge off
of the extra heat, but the factory one would still be there to make sure the
temp is above 190F. A sound design.
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If you wanted to add a huge oil cooler, and bypass the factory one, you
might be able to get temps down near 180F, but then you would need a
thermostat as well. And the oil would warm up more slowly increasing rod
bearing wear.....
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Past 260-280F dino oil breaks down quicker (carbonizes) leaving deposits,
etc. If you see oil temps like that you would be well advised to change the
oil after every event. Synthetic has much more temp resistance, and leave
much less deposits anyway, so that oil changes due to high temp would not be
necessary. Another thing that happens with very hot dino oil is that some of
it literally evaporates, (the low molecular weight organics) causing your
oil level to drop and forcing you to add oil. That doesn't happen with the
synthetics either. Those (dino oil) deposits cause both engine wear and the
piston carbon deposits increase the pinging tendency upping the octane
requirement, which may impact the timing tune-up.... another topic - but
yes, it's all related.
Lee