My son and I were always skeptical about the "oil and gas resistant" claims of the various brands of "rattle can" engine paints. About 2 years ago we set up a good side-by-side comparison of the 3 major (only?) players- namely, VHT, Duplicolor, and Rustoleum. We were very careful to use identical metals (condition, type, and prep) for the testing, and (very important) we also used the (engine primer") proprietary to each brand. Finally, we made sure and let each paint brand properly/fully cure as per their respective manufacturer's instructions. (Typically 7 days MINIMUM)
While all of the paints were oil and gas "resistant", NOT "proof", over their non-engine paint counterparts, the VHT was the clear winner over both Duplicolor and Rustoleum which performed about the same. I would "guesstimate" that the VHT performed (lasted longer) by around 20-25% over the other brands when subject to gasoline. For our testing we tried both dripping gasoline and then rubbing a gasoline-soaked rag on the painted surface. While the VHT did better, it comes at a price- It is significantly more difficult to apply w/o drips/sags. You have to do more lighter coats to get the same coverage.
Michael