It mostly comes down to the site. Now that we're all designing for responsive, it's probably more prudent to have a responsive logo--as in, multiple versions of your logo, depending on the screen resolution. Having just a small logo on the left works well for all screens, but imo it seems barren on a larger monitor.
Yup... I don't think there is any real single answer, just options. IMHO, I believe a car site should have a car logo, just as you have. Sure, its going to be big on full screen, though who cares if you have the space.
I would get around issues as a two stage logo, being the image of the car would be on a sprite with other forum images (one-time request), loading as a background on the left as is for full screen views. I would then use a font either loaded locally or a default one (if possible) for the text. That way the text is all just text and CSS. Scale it appropriately using media queries to remove the car from smaller screens, whilst reducing the text. That way you can reduce the header heights and such all in one go with media queries, having the professional text styled as you have it without sacrifice, but fitting all devices. You could even drop the URL portion that way on phones, having just the name showing so its all business getting at content quickly.
That is just me though... I'm all for reducing requests on the server as much as practicably possible whilst meeting all devices.
Again though, there are so many ways you could do what you want to do... depending on what you ultimately want to achieve.
It does depend on the forum type. I felt it was important on my site to go with something impressive (competitor site still running phpBB on default skin). Could have just used the logo, but the cars define the site so wanted something unique looking.
Will probably refresh the image with a different picture when we go to 1.2.