The subject of
oil has been discussed many times in the past. Look for the old threads to get the complete story. Many of the high performance engine builders have said the
synthetic oils tend to make the engines leak. I myself use the Castrol 10W-40. I have had many high performance cars and bikes over the years and have never had any problems with the Castrol. Another
oil, I have used and liked, is Kendal GT1 10W-40. IMHO, either of these oils will work great in your Cobra.
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"The 427 Cobra is easily the highest performance car ever sold for street use. A decent 427 - not the worst, not the best, will go from zero to 100 mph and back down again to zero in less than 14 seconds. All thing considered, you can put together a pretty good argument that the 427 Cobra is the ultimate performance car, judged on any basis you want to name." Taken from; Corvette, The Sensuous American
