Any idea on the shelf life of Chevron Techron Fuel Injector Cleaner? I have a couple of bottles left that are probably 5-6 years old. Since I always use Top Tier gas, I only use Techron occasionally, maybe once every 5,000 - 10,000 miles. Two engines are GM DI, not sure about the 2012 Acura 3.7L. Read an article that said Honda announced DI in November 2011. Thanks.