I've used it on my wife's 2001 GMC Jimmy. I put some in the fuel tank and some in the oil. When I had the oil changed I noticed really small black pieces of build-up came out that I had never seen before. I think the ratio is 1 oz. to 1 gallon of fuel and 1.5 oz. for each quart of oil. I read somewhere to change the oil after about 100-150 miles of driving. I haven't put any in the vacuum hose yet but that is coming. It says to slowly pour 1/3 to 1/2 of a can into the vacuum hose of a warm engine, turn engine off for ten minutes, then restart engine. Exhaust will be extreme for a short period.