I'm probably in the minority here, but I abandoned the use of any form of Dolby on a cassette machine many, many years ago and never missed it. My main cassette deck is a Nakamichi 482Z. Now it won't record any more (can't be fixed as the critical part doesn't exist, except in other units) but it still plays the old recordings fine.
Your car machine is likely to have Dolby B, if anything. Dolby C has a stronger level of processing and goes lower in frequency, yielding more apparent increase in S/N. I've forgotten the details of Dolby S.
I prefer to live with the hiss since I think the actual sound is better than with Dolby. I always hated being able to hear the processing and the change in the noise floor when listening on headphones when strong high frequency transients like drum machine parts were recorded. It's much more natural without that processing. YMMV.
Cheers,
Otto
As I recall Dolby S was a consumer version of SR which was used professionally and on feature movie release prints. Stereo feature movies on ordinary 35mm film were made possible by Dolby reducing the noise on the two now much narrower optical tracks.
Actually I think, Otto, you would be in the majority of home users who also abandoned using Dolby on cassettes.
Dolby was used very sucessfully at the pro level from the mid 60's on but this was with pro machines which could easily be aligned and serviced. Dolby was cruel on any non linearity in the record/playback chain but the public mostly wasnt told that downside. Many if not most cassette machines had no external facilities for aligning bias/record level, were only 2 head types, and there were other ways for the alignment to go out and for the Dolby tracking to go off by a little or by a lot, and sound terrible.
But I disagree that Dolby always sounded bad, even on cassette. On a well set up recorder you would be struggling to hear any artifacts, just less hiss. Ray Dolby did his homework.
For many years I recorded conference speakers direct to cassette and I always recorded with Dolby B switched in. In no way did I expect the Dolby tracking to stay accurate right through to consumer casette copies played on their home machines, but it meant that the original recording contained a lot less hiss than it otherwise would, or put another way, more headroom available. These days I can go back to those original recordings, personally decode them accurately, with adjustments if needed, and have a recording which is much less hissy than if there had been no NR, and has few if any mistracking artifacts.
This to me is much preferable to having to resort to "after the fact" denoising and noise gates, which are all the rage these days, but which by nature cannot retrieve information that was buried in tape hiss. You have to reduce noise at the beginning. After that is too late.
As for Dolby decoding working consistently in a car cassette player, a bit of a gamble IMO. Too many things to go wrong.
Tim