As with anything, it's not that simple. Longer oil change intervals don't necessarily account for every driver and driving condition, and there's little margin for error. In the day of 3 months or 3,000 miles, missing an extra month or an extra thousand miles didn't extend into the realm of sludge build-up.
But if your recommended interval is 6,500 miles and you go over another thousand, you are well beyond acid build-up and getting into heavy sludge territory. Another consideration that we will cover in a post very soon is Gasoline Direct Injection. These systems should be serviced regularly during an oil change, or there is undoubtedly significant trouble ahead. Injector and induction cleaning should always take place before draining the old oil.
It is essential to follow mileage intervals very closely and complete the service items shown in your owner's manual. Be careful not to fall victim to the $24.00 oil change that's a gateway to expensive, bloated service tables created by some dealers. The truth directly from the manufacturer is in your manual. Most importantly, consider the severe service schedule: Central Florida's stop-and-go driving, short trips, dusty conditions, and hot weather. Likewise, Uber or Lyft drivers, those towing boats, and heavy hauling are also severe service conditions. Every day we see evidence of harsh Central Florida driving conditions. We advise most customers to observe the "severe conditions" service schedules.