That’s the way Savage Most people just look at the viscosity rating and that’s it!!!!!!!!! The Viscosity is the pour-ability of Oil at a “defined” temperature. A Quote from the FPV and the Ford Service Training Institute. F6-270-Turbo Recommended Mineral oil SAE viscosity grade 15w~40 WARNING: Use of alternative oils may result in degraded performance, fuel economy and emissions. Do not use non-detergent or API class SC, SD, SE, SF, SG, or SH oils or additives. For example the 0W~40 Synthetic oil question not only meets FORDS specifications but exceeds it. How can you void warranty when you use oil which exceeds the factory specification???????? Some dealers are smart enough to know and some are not. My T3 came out of Fords factory with 0W~40 oil and every time the Ford dealer serviced it he would use Mineral oil 15W~40.. Time and time again I told them it was wrong yet they still used the wrong oil next service. After one service I fronted the service manager and he told me outright that (these dinosaur engines CAN NOT run a 0 weight oil) So I promptly introduced him to the Ford spec sheet stipulating 0W~40 FormulaR .. Needless to say he was at first lost for words then promptly apologized, then changed my oil to FormulaR at no cost. If you are so worried about the viscosity ONLY then do a test: In my BF F6 the oil pressure when hot at idle is only on the first mark on the gauge (lucky to be 1/8) with factory Oil from new. Change it to 10W~60 FormulaR and the oil pressure sits just a whisker under ½ at Idle. Then with 0W~40 FormulaR it sits on about 1/3 at idle HOT which is just about spot on in my book “if” I was only concerned about the Viscosity. Mmm strange how a 0w Synthetic oil hold its viscosity better when hot than 15w mineral oil????? One of the many but main reasons for switching to Synthetic oil is its longevity…. In theory it should last you twice as long as normal mineral oil and as such maintain it integrity over longer service periods under extreme operating conditions thus reducing engine wear and maintenance costs. What we usually see here is a switch to it not for its longevity but its ability to maintain engine component protection whilst running increased power over that same service period. Simply put in the transport industry you use synthetics and extend our service periods from 20,000km to anything as much as 60,000km subject to the TBM or schedule oil sampling. Your car! Use whatever oil turns you on! But at least check the specifications before you condemn an oil. <{POST_SNAPBACK}> Well said, Castrol EDGE, good oil for Turbos, I use BP Visco 5000, 5w-40, also good oil. Motor purrs like a kitten, Turbo spools great. If you look at your OIL CAP, xx-40, xx-50 is stated. For interesting oil articles go to www.bobistheoilguy.com Oil is not only Lubricant is also used for cooling, thinner oil removes heat quicker with its higher flow rate, thicker oils dont flow as quick. Thinner Oil also gets in to clearances better.