t3chn1c0 asked if this would work on a 4.0L jeep. I read this & I have a 92 ford w/ 300 l-6 & I have 89 xj w/ 4.0. I pulled cap off the ford & it fit on the jeep. My 92 has a small cap like the jeep. I am going to get the larger cap & it should work. I'll keep you posted.