If you do actually use the car a lot when the temperatures are near and below freezing, then that grade would fit the bill. But I guess that you get hot weather in summer, just as we do in Scotland sometimes and so the recommended 20W50 would be more appropriate in summer.I live in the US in the northeast where it gets cold in the winters. I am currently using 10W30 oil in my '70 500F. Is this wrong?
If you do actually use the car a lot when the temperatures are near and below freezing, then that grade would fit the bill. But I guess that you get hot weather in summer, just as we do in Scotland sometimes and so the recommended 20W50 would be more appropriate in summer.
I am not an expert but I don't think you would be damaging the engine other than possibly encouraging leakage and burning a bit more oil past the piston rings and valves.