I have only had to get recovered home once. My car (Vauxhall Carlton), had suddenly developed a rattle and blue smoke under load. I was in Greenock, so phoned my son-in-law in Fife, and he said sounds like a broken ring, bring it home and I'll strip it down.
I also noticed the auto transmission slipping, so checked the fluid and it needed topped up! I thought it was two separate problems. On the M80, half way home, and the automatic transmission gave up the ghost. And that is when the RAC came to my rescue. Once again the gearbox was dry!
Before doing any work on engine I decided to phone a transmission specialist. Depending on his diagnosis depended on whether the scrappy got it or my son-in-law. When I told him the oil had disappeared and there was no leak his reply was, "and the engine rattles and blows blue smoke".
It was the modulator valve. The diaphragm was leaking and the carb was sucking the oil out of the gearbox. £50 replaced the valve, filter and fluid and I never had anymore problems.
I was so grateful for the recovery wagon and the RAC's assistance. Like any insurance, it seems expensive until you need to use it.