Onboard refueling control technology has been successfully applied to two vehicles with 98+% efficiency without a vapor seal in tests with 11.8 RVP fuel at 88°F. The elements of the onboard system were constructed out of components similar to those found in current automotive evaporative control systems. The entire system was designed for minimum pressure drop so that a mechanical or liquid seal is not necessary. The flow of fuel into the tank provides enough pressure to force the tank vapors into the canister. Control of evaporative emissions was improved to the extent that the 2 grams/test standard for a 9 RVP fuel was met with a fuel of 11.8 RVP. Effects on tailpipe emissions, and canister size are also discussed.