Since I got to work early this morning, I will take a few minutes to type my opinion.
Disclaimer, I stock Redline 10-20-30 and 40 race oil all the time. I am a Schaefer distributer and also sell a lot of Royale purple.
Part 1; For a race car you want race oil. Street oils and race oils use the same base stocks, but the additive package is different. Street oils have additives for long life, high detergent, strict emmissions, gas mileage, and relatively low RPM. In a race environment, you do not want any of those qualities. In fact you want just the opposite in many cases. We change our oil regularly, want performance not MPG, and need the high RPM additives not found in street oil.
Part 2; Synthetic oil is still dead dinosaurs. Different weight oils have different size molecules. Imagine, 10w is golf ball sized molecules, 20w is tennis balls, 30w is basket balls and 40 is beachball sized. Pour your multi weight oil on the floor in a single layer of molecules/balls and lay a sheet of plywood over the oil. The big molecules are going to do all the work. If you have only one size molecule in that bottle, the work is shared among the entire bottle.
Part 3; Your engine builder has determined what bearing clearance you have. If you have golf ball size bearing clearance, you need golf ball sized molecules. Imagine the force required to squeeze a beach ball into the space of a golf ball. It will go, but it takes a lot of effort that results in heat and lost power. Matching the oil molecules to the bearing clearance is important. It is also almost free horsepower.
Conclusion; Since we can not measure the molecule size and most of us don't know our bearing clearance, what do we do? First, get a real oil pressure gauge and find out what your oil pressure is at the end of a session, fully warmed, at race speed (6500rpm). I have found 40-45psi to be the optimum number. Anything below that can cause engine wear. Anything above that is wasted power. Then adjust to a thicker or thinner oil as needed.
Dyno testing; I have tested a lot of oil on the dyno. And yes it does make a difference. We tested 19 different oils from all the big manufacturers on the same day, in the same car. I found a 9 horsepower difference between the best and worst. Amazingly the best and worst where different weights from the same company. Do not believe the commercials you see on NASCAR television and in magazine ads. Expensive is not always better. I use Schaeffer in all my cars, from front runners to backmarkers. I buy it in 55 gallon drums for use in the shop.
Even cheap Walmart oil will work. But this is one of those little things that seperate a 100% car from the rest. A high school teacher says "Knowledge is power". In this case "knowledge is horsepower".
dave
Dave Wheeler
Advanced Autosports, the nations most complete Spec Miata shop
Author, Spec Miata Constructors Guide, version 1 and 2.0
Building Championship winning cars since 1995
4 time Central Division Spec Miata Champion car builder 2012-2013-2014-2017
Back to Back June Sprints Spec Miata 1-2 finishes 2016 and 2017
5 time June Sprints winner in Mazda's
6 Time Northern Conference Champion Car Builder
2014 SCCA Majors National point Champion car builder
2014 SCCA Runoffs winner, T4 (Bender)
2014 Central Division Champion, ITS (Wheeler)
2013 Thunderhill 25 hour winning crew chief
2007 June Sprints winner, (GT1, Mohrhauser)
Over 200 race wins and counting.
www.advanced-autosports.com
dave@advanced-autosports.com
608-313-1230