FYI guys:
From an oil specialist:
"If your car is being used for mostly street use then you could use Mobil 1 0w40. For a balanced track and street use Shell Helix Ultra 5w40, it has high zinc and phosphorous contents which you want for wear resistance and load bearing. The VI of that oil is 187...You will be hard pressed to find another oil with such a high viscosity index. The VI tells you how much the oil "thins" as it is loaded with heat and mechanical stress, a high VI means it stays more consistent and doesnt burn so easily and it doesnt readily get so thin that metal to metal contact can occur. Dont be mislead by flash points, they are done by either PMCC method or COC and with different ASTM methods (typically D92 or D93) rather ignore this number...With Helix Ultra 5w40 you can go 15 000 to 20 000 km on a heavily tuned car making big power. On mobil 1 0w40, probably 15 000km to be safe... If you use the car extensively for tract work my advice is use Castrol Edge 10w60, its not fully synthetic but is very robust, BMW use this exclusively in their M cars...But dont go more than 7500 -10 000km on this oil, when it does burn it will leave deposits.
As a general rule of thumb, only use an oil if its 5w40 WITH (this is vitally important) a VI of over 170. That way you know it is a true PAO/ester based synthetic and its not bound to low emission engines, those oils are bad for wear but good for emissions. With the Supra, I'm sure you dont really care about emissions. One other thing, you want a sulphated ash content of 1.1% - 1.5%, this is an indicator of detergent and dispersant additives in the oil and are a very good thing!
I hope this helps and that you find an oil that makes you happy. I have used Shell Helix Ultra in every car I own, except our diesels which run Shell Rimula R6m 10w40 synthetic. My ST225 06' which I owned from new uses Helix ultra and to this day NEVER requires a top up between 20 000km intervals, I have almost 190 000km on the car, zero turbo problems, making 208wkw and its been running mods since 6 months of me owning it way back in 06'."
Some more info on the TDS of Castrol Edge 5w40:
Castrol Edge 5w40 Technical Data sheets:
http://www.castrol.com/liveassets/b...ts/downloads/p,q/Edge_BLACK_PDS_Sept_2011.pdf
http://www.castrol.com/liveassets/b...ts/downloads/p,q/Edge_BLACK_PDS_Sept_2011.pdf
PS: Find Attached documents to this post to see TDS of Shell Helix Ultra 5w40 and 10w60 , as well as Castrol 10w60 Professional and Castrol Edge Sport 10w60
I hope this helps :=):