Regarding fuel used by automobiles...is it OK to own a car or not (or how about a motorbike)?

My question may sound rather odd and a bit extreme to some people (especially since i'm writing from the UK where we rely heavily on the automobile) but I have for the last few months had alot of doubts and thoughts in my mind regarding the toxic waste gases produce by cars and other automobiles. My concern is this: In Islam we have a duty to protect the environment we live in and not damage natural habitats of other living beings but at the same time we are using motor vehicles which spew out gases and which (in theory) assist in harming the environment through acid rain etc or is burning fossil fuels just the same as burning firewood? I know the car is an indispensable part of todays busy lifestyle and helps save alot of time and energy (which could even be used for the deen) but is it OK to own a car or not (or how about a motorbike)? Presumably I assume it's OK since the advantages outweigh the disadvantages and it could be used for the progression of the deen but I still want to be sure. I hope you can shed some light on this matter Mufti saab, jazakallah khair.