Preparing for my 100k mile tune-up I put Seafoam in the oil and gas tank. I've used it plenty before with a few negative results. Previously the oil sludge the Seafoam broke free clogged the VTEC filter on my Honda. I didn't expect any drawbacks in the Suburban though. After two days (40 miles) it started up with one of the valves stuck and just clanging away. I spent this morning putting in new plugs and wires with fresh oil. It cured the sticking valve and no further trouble. Just wanted to add my $.02 on Seafoam. I'll continue to use as I've not seen anything work as well. I hear BG products are the best but they're 2.5 times the cost of Seafoam. For future Seafoam users I'd recommend using Seafoam intermittently and not waiting to 100k miles like I did.