Since your 2005 Lotus Exige 2ZZ-GE NA does some road race/endurance type track events you can use either the Royal Purple HPS 10W-40 (part #31140, quart bottle), or Royal Purple XPR 10W-40 (part #01041, quart bottle).

If this Lotus Exige with the 2ZZ-GE NA engine was only being used for street driving (daily driving, spirited driving) with some occasional drag race we would recommend Royal Purple HPS 5W-30 (part #31530, quart bottle), or Royal Purple XPR 5W-30 (part #01021, quart bottle).

For daily driver duty and recreational use (spirited driving, occasional racing, etc.), the Royal Purple HPS product line will be the best overall choice.

HPS: http://royalpurpleconsumer.com/product- ... -motor-oil

For a dedicated competition vehicle, or if you just want the absolute best performance and protection, the Royal Purple XPR engine oils are the best choice.

XPR: http://royalpurpleconsumer.com/product- ... racing-oil

Since the HPS and XPR series are not licensed they do not have any chemistry restrictions they have to meet, so they will contain high levels of the ZDDP appropriate for use with performance flat tappet camshafts. The XPR series is going to be the most robust formulation we offer, but it is a little pricey for a recreational use applications. The HPS does offer a significant portion of what the XPR provides at a much lower price. However, both series contains our proprietary Synerlec additive technology.

Both series contains our proprietary Synerlec additive technology.

Synerlec: http://www.royalpurpleconsumer.com/abou ... /synerlec/

As far as oil temperature readings, there is no minimum and the maximum would need to be kept under the boiling point, ~600 degrees F (315 °C !). The engine would likely fail before you would even reach the boiling point of the engine oil.

Racing oil change intervals:

Racing oil change intervals are pretty tough to predict on your 2005 Lotus. However our general guide is that you can often double and sometimes even triple whatever oil change intervals were successful for you when you were using your previous brand of racing oil.

The variables that influence intervals include but are not limited to, number of races run per year, the total amount of oil your engine holds, the effectiveness of your oil cooler design, the length of time your oil is at peak temperatures (and what those temperatures are), and the amount of fuel dilution build up.

Fuel dilution can build up and become an issue over time, an easy low buck industry proven testing method is the oil blotter test.

Oil Blotter Test:
The Blotter Spot Method - Sample Preparation and Test Procedure: A Quick Guide : http://www.machinerylubrication.com/Rea ... pot-method
An Unusual Twist to the Blotter Test - The Lantos Method : http://www.machinerylubrication.com/Rea ... est-lantos
Spot Check Your Car's Oil : http://www.machinerylubrication.com/Rea ... ck-car-oil

If you have an very large oil capacity, sending an oil sample to a testing lab may be a financially viable option for you. Please feel free to email me a copy of the test results and either myself or my supervisor Chris Barker will be happy to go over your results and advise.

http://www.wearcheck.com/
http://www.blackstone-labs.com/

Thank you for choosing Royal Purple, and have a great day!

Best Regards