Here is an example of why it depends. I just got my daughter's used oil analysis results back. I changed her Castrol edge 5w30 oil at 3,694 miles which she drove over six months. The label says the oil is good for 20k miles or 1 year, Mazda recommends 10k miles intervals for oil changes. The filter is good for 10k miles as well.
Her wear metals were good and below 5ppm/1,000 miles, however her fuel dilution percent was 2.9% which is at a percent where it can start to reduce the oil viscosity at an exponential rate causing it to shear below the 5w30 grade and into a 0w20 territory. Her viscosity had not sheared out of grade yet but I guarantee it would have if done at the dealer 10k mile interval. Maybe it could be stretched to 5k miles but I'd rather not risk higher wear metal deposits and potentially more engine wear.
Based on her results and now the trend across 3 different oil changes, I want her oil changed every 3,000 miles or every six months. She mostly drives to school and back which is 2 miles each way. Occasionally she drives on the freeway but the more frequent short trips means it is better to change her oil more often. She doesn't drive far enough to get the oil to operating temperature which, if she did, would help reduce fuel dilution.
That works for her car the way she drives it and based on the oil we use. For my wife and I who are on the freeway more often, our sweet spot is 5-6k miles. We both have turbo direct injection engines. I drive more stop and go rush hour traffic miles compared to city, while she is probably 50/50 city/highway.
Her wear metals were good and below 5ppm/1,000 miles, however her fuel dilution percent was 2.9% which is at a percent where it can start to reduce the oil viscosity at an exponential rate causing it to shear below the 5w30 grade and into a 0w20 territory. Her viscosity had not sheared out of grade yet but I guarantee it would have if done at the dealer 10k mile interval. Maybe it could be stretched to 5k miles but I'd rather not risk higher wear metal deposits and potentially more engine wear.
Based on her results and now the trend across 3 different oil changes, I want her oil changed every 3,000 miles or every six months. She mostly drives to school and back which is 2 miles each way. Occasionally she drives on the freeway but the more frequent short trips means it is better to change her oil more often. She doesn't drive far enough to get the oil to operating temperature which, if she did, would help reduce fuel dilution.
That works for her car the way she drives it and based on the oil we use. For my wife and I who are on the freeway more often, our sweet spot is 5-6k miles. We both have turbo direct injection engines. I drive more stop and go rush hour traffic miles compared to city, while she is probably 50/50 city/highway.