Originally Posted by r.furborough
On the contrary, gasoline used to be added to diesel fuel during the winter months by truck dirvers to prevent waxing, it used to be common practice and if used in moderation caused no engine damage.
Maybe that used to be the case, but not any more. Modern diesels use very high pressure pumps. The lubricity of modern ultra-low-sulphur diesel is marginal for these pumps, even when un-diluted. If you add gasoline to it, you could lower the lubricity below an acceptable threshold and cause severe, and incredibly expensive, damage to the fuel system.
In fact there has been discussion on the sailing forums
of the marginal lubricity of modern ULSD, and the need for additives to increase lubricity, even on older engines with much lower pressure fuel pumps.
On the latest generation of "clean diesels", in the event of fuel pump
failure, VW has taken to testing the fuel for any gasoline, and will deny your warranty claim if any is present. The repair cost is about $7000.
If you want to add something to diesel, how about one of the excellent additives designed for the job?