Hi. As per the other contributors, the long-term answer is "No". I'm not impressed by 'tyre-softeners' on sale from various suppliers; it smells suspiciously like old-type "3-in-1" oil and all oils will eventually combine with the oxide and braid deposits from the rails to build up a red-ish hard patina on the tyre tread. This can be improved for a while by scrubbing with a 500 grit wet 'n' dry paper.
Newer Scalextric models (since around 2000) tend to come with a better range of 'rubber' compounds which are softer & grippier on "Sport" track. I don't like silicones or urethanes as they seem crude and often leak agents in long-term storage (e.g. the tyres supplied on the FLY Vipers).
I genuinely have no link or business arrangement with Sandbach Slot Cars on eBay UK, but for your older cars, from 70s Mini 1275GTs, Capris, Datsuns etc, through 80's F1 turbos onwards, Group C GTs etc, I find Mark's expanding range of Shore rubber repro tyres are excellent quality and value, being very close to the originals, well-finished, grippy and reasonably priced.