Rather than backing down, Valvoline is holding its ground, and turns up the heat. Marketers say the received a letter from Valvoline providing additional information and data to support Valvoline SynPower's significant performance advantage versus Mobil 1. In addition, marketers say the letter turns the table on ExxonMobil's challenge and Valvoline is now challenging ExxonMobil's claim for its Mobil 1 5W-30. According to the letter, Valvoline says the company conducted a number of tests and commissioned an independent laboratory to evaluate the performance of SynPower and Mobil 1 in the Sequence IVA wear test. Marketers were told the tests were run on a 5W-30 since it's the top selling grade. Now for the interesting part... According to a letter Valvoline marketers received, the result from Valvoline's testing indicate: * Valvoline SynPower's 5W-30 wear performance is at least four times better than Mobil 1 5W-30 * Mobil 1 5W-30 does not meet minimum API SM or ILSAC GF-4 specification because of its inferior performance in the Sequence IVA wear test The letter reportedly goes on to say that Valvoline notified ExxonMobil of the failed test results in September and that the company take appropriate action regarding their claim that Mobil 1 meets ILSAC GF-4 and API SM specifications, or provide substantiation that they in fact meet these specifications. As of today, Valvoline told JobbersWorld, ExxonMobil has been silent.