This thing worked amazingly for some of the clogged grease fittings on my twenty-year-old Toro Proline walk behind lawnmower; I had to use it several times on some of the fittings, but they all finally came clean. I used light machine oil, but understand from some reviewers here on Amazon and elsewhere that I could have used WD-40 or even mineral spirits. It worked great for me, and I intend to use it occasionally just to keep the fittings clean, as I had ignorantly and unintentionally let some of them go too long between maintenance and discovered the hard way that machines just won't work without proper maintenance.