It is more likely that it will down to the type of driving you are doing. An engine that is involved with more stop start work, or sitting in ques for periods of time, will not run as effeciently as one cruising on a motorway. Many years ago I was involved with a lub oil company and we carried out analysis of engine oil from identical vehicles some involved in mainly city operations and some on motorway work. The latter ones consistantly achieved 10 times the length required between oil changes.
From a personal perspective I run a 2.2 auto and it has covered circa 5k since last oil change and the oil still looks good. Have you changed the type of oil recently as a "higher spec" oil can some times clean out the gunk left by a previous oil. Y ou can some times then encounter oil leak problems so best to keep to the same grade.
Hope it helps
