If it's a flyer then you'll definitely need much larger text, there's nothing wrong with a simplified flyer (i.e. no colour, short, concise text with like standard font centering etc.) if it's not a professional business. The last thing you want customers doing is driving over thinking it's some top-end car maintenance shop (or even worse: thinking that it's beyond their league) if it's not.
I'm not sure what your business strategy is, whether it's cost leadership (low prices) or product differentiation ("we show your car love which you can't get elsewhere, or do some sort of special vacuuming which other places don't") but that's what you need to show on your flyer, information about the service and your contact details. Don't make it wordy, most customers aren't going to be calling you because your flyer looks awesome but because they see a service being offered which they need/value.
I don't think there's any need to make an elaborate over-the-top flyer, all of Cookie's advice sounds good (to me anyway
).
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