Of course! Being a mustachian is about being *smart* with your money, it doesn't mean living the life of a monk. Everyone chooses things that are "worth it" to spend on... the point is that it's supposed to be a *CALCULATED* risk. Meaning, you know exactly how much longer you're going to have to be an employee (how long it's going to delay your FIRE) with each and every purchase you make. So it the value/cost ratio is high enough to you, and you know it's going to cost X weeks/months/years of retirement but you've decided it's worth it for you to make the trade, then you can do it.
In fact, I'd say being a car enthusiast might make it *easier* to be a Mustachian! That means you know enough about cars to not get ripped off like so many people do! It means you know, even more than most people, how stupid it is to buy a brand-new car and take such a massive depreciation hit the day you drive it off the lot. So you won't do that. You know how a car should be maintained, so you end up paying less in repairs than most people (and less for the maintenance too! because you can do a lot of it yourself). It means when you do buy a car, whether it's an econobox or a muscle car, you're going to pay a fair price for it and not get ripped off because you're too lazy to look up the kelly blue book value before you buy. And you're smart enough not to get ripped off by ever doing a trade-in. You know exactly how much gas mileage you're losing by driving a Mustang instead of a Metro, so you're not going to do something stupid like drive your muscle car on a 100-mile commute every day. You'll either keep your commute ultra-short, or just have your fun car as a weekend thing and get something more efficient for the daily driver.
Etc etc, it goes on... being "into" cars means you can buy the cars you want and *still* pay less than most people do!
(I enjoy the same privilege but with computers... I've been into technology my whole life so I know exactly what devices I need to buy to meet my uses, and which ones I want for "fun", and which ones don't appeal to me even though I've never tried them, because I know everything about them so I don't have to get my info from salespeople that have their own agenda, I don't have to pay somebody else to replace a failed hard drive or whatever, I know exactly what free software I can get that does the exact same thing as expensive commercial software, etc etc. In the end, it means I get to enjoy my "toys/gadgets" and still pay less than the typical person does... because I do things like, instead of paying several hundred extra for a "smart tv" I get a regular one and buy a $35 chromecast stick, etc etc)