So an idea I've had for a while is wondering if the increase in the oceans are helped along by the water vapor released by cars.

So I did some math.

Well ok, not alot.
I used this figure:http://blueskymodel.org/gallon-gas
(Scroll to the bottom) of 8.3 lbs/gallon of gas.

Then this: https://www.eia.gov/tools/faqs/faq.cfm?id=23&t=10
136 Billion gallons of gas used in the USA in 2014

Multiply 1,128.8 bilion lbs of water.
Density of water as a liquid:
http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html
8.3 lbs/gallon
(Convenient)
Which basically gives 136 billion gallons of water produced per year in the US by car exhaust. 

Thats a lot of water.  Not exactly lake amount but for the US only that seems like alot yearly.

yeah, density of water is really important when we are talking about increasing in the oceans, especially when the temperature is changing
https://amazingconverter.com/density-converter/density-of-water-lb-ft3