The release of 60 million barrels of crude oil and its derivatives from the Strategic Petroleum Reserve over 30 days is obviously a short term supply, as the crude oil is not produced, it is simply released from storage. The global crude oil market consumes approximately 88 million bpd (according to IEA), so this 30 day release of 2 million bpd is 2.25% of the daily oil consumption.
So, imagine what would happen to crude oil prices if just 2.25% of crude oil demand was reduced PERMANENTLY by conversion of the demand to CNG?
According to recent news reports, the US could lose up to $1.5 Billion due to buying high and selling low on the 30 million bbls it's releasing from the SPR. That's just for 30 days of benefit, because on day 31 guess what the price of crude oil will do? Go back up!
Meanwhile, House Bill 1380, the Nat Gas Act, would cost between $5 and $9 Billion, but would create PERMANENTLY reduced oil consumption.
The US release of SPR for a 30 day price benefit (which will actually INCREASE oil price by encouraging demand and discouraging increased supply by suppressing price in the near term) makes the case for why the US should incent CNG adoption.