The short answer
- Conventional oil: 3,000 to 5,000 miles
- Synthetic blend: 5,000 to 7,500 miles
- Full synthetic: 7,500 to 10,000 miles, sometimes 15,000 in newer European cars
- Trust your manufacturer's recommendation in the owner's manual
- Trust your oil-life monitor if your car has one — they're surprisingly accurate
Why intervals got longer
Two reasons. First, modern synthetics resist breakdown at high temperatures far better than old conventional oils. Second, modern engines are tighter — fewer contaminants get into the oil in the first place. Combined, that means a synthetic oil can do its job for two to three times longer than a conventional oil from the 1970s.
When you should go shorter than the manual says
Some driving conditions are harder on oil than the manufacturer's average assumes. If most of your driving is:
- Short trips under 10 minutes (engine never fully warms up — water and fuel build up in the oil)
- Stop-and-go traffic in Dallas-area heat
- Towing or hauling heavy loads regularly
- Dusty conditions or unpaved roads
- Track days or hard performance driving
...then run the conservative side of the recommended range. That doesn't mean 3,000 miles for synthetic — but if your manual says '7,500 to 10,000,' do 7,500.
Texas-specific notes
Heat and dust are the two North Texas factors. Sustained 100°F+ summer driving puts more thermal stress on oil. If your car spends August idling in carpools, lean toward the shorter end of the interval. If it spends August in a covered garage and most of its driving is highway, you're fine going long.
What to do if you can't remember the last change
Change it. Then start tracking. Most modern cars track oil life in the dashboard menu — learn how to read it. If yours doesn't, just write the mileage on a sticker (we'll do that for you) and check it monthly.
