greenpool

Hi Guys, let me come clean and let you know that i know very little about cars : \ i just purchased skyline v35 and found that it had a switch to turn VSD on and off. i honestly don't know what this..i've tried searching google but i couldn't find anything conclusive. can one of you car-smart people tell me what this is and whats the benefit of having it on? (and if there are any disadvantages like higher fuel consumption etc.) thanks in advance! p.s: hope this is the right forum..