The valid range limits for the Simple and Complex Models given in § 80.42(c)(1) and § 80.45(f)(1), respectively, give the ranges outside of which fuels cannot be evaluated with the compliance models. What are you supposed to use if the fuels to be evaluated are outside of the specified valid range limits?
If a target fuel contains one or more fuel parameters which are outside the valid range limits, the compliance models generally cannot be used to evaluate that fuel. To use the compliance models, a refiner may reformulate the fuel such that it falls within the valid range limits. A refiner may also augment the Complex Model through vehicle testing to widen the valid range limits.
Finally, if the refiner's individual 1990 baseline fuel contains any parameters which fall outside the specified valid range limits, he may qualify for extension of the valid range per § 80.91(f)(2)(ii). This paragraph on valid range extension has been clarified in the Direct Final Rulemaking signed on June 27, 1994. (7/1/94)
This question and answer was posted at List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (pdf)