Blue smoke

[Lewis8144]

I was on the M6 (2nd biggest Carpark in the Uk) and going past Manchester Liverpool etc so the speed was varying from walking pace to 30-40 and back for about a1-1/2 hours. Traffic then sped up and I was doing 75-80 when I happened to see a puff of blue some come from the exhaust. The engine oil was106°, no loss of power or anything else untoward. Slowed down to 70 then after 10-15 miles stayed around 75. Is the smoke anything to worry about or just a result of all the crawling speed?

Thanks in advance for any answers