Hello Zulfiqar,
I've asked the same question, as in subject, to many experts by personally meeting them and all of them agreed that "Quality of Fuel does affect the Quality of Engine oil". But as I've gone through many posts and was scratching my head that Zulfiqar said it doesn't matter much but the cold engine running is not good.
And yet keeping your given answer as authentic, I've contacted with Liqui Moly. And their answer is as below.
Question from GoodMan7
In your previous email, you mentioned "because of poor quality of fuel in Pak." your recommended change intervals for engine oils are low. Well I totally agree with that. But we have one very very good mechanical engineer (especially for car engines, nick name Xulfiqar) and according to him, Fuel Quality Doesn't affect on Engine oil much but running cold engine is not good instead. Could you please help me to understand that how the fuel quality affects the life of engine oil?
Answer from Steffen, Liqui Moly's head office Germany.
poor fuel quality is one of the most common reasons for early oil break down! High water and sulfur contend in the fuel, low octane rate - all this creates deposits at the inlet valves and clogges up the injectors. Unburned fuel will come into the engine oil and thins the oil and creates acids. So the oil has a accelerated loss of performance. This is the reason why you have to change the oil earlier in case of poor fuel quality.
Looking forward your further comments.