3,750 mile oil change intervals (why such an odd number)

No, it is just half of 7,500 which is probably the change interval for "normal" service and 3,750 is the "severe" service recommendation.

Most cars today recommend 7500 miles for normal service. Half that for severe, thus the 3750. You may fall at either of those or someplace in between, depending on your driving conditions and habits. I shoot for 7000 miles, but I drive under good conditions, half highway driving. Short trips in winter lowers the distance, as does hot summer in the desert. You may want to cahge ad different intervals in different seasons.

Read the manual, assess your driving, choose a miles that suits you. Oil change outfits still say 3000 miles, but they are motivated by profit, not your well being. Some call it cheap insurance, I call it a rip off. I've never encountered an oil related engine problem and I often keep a car for

200,000 miles.

I change at either 5,000 miles or 10,000 miles. I use 5,000 for vehicles still in warranty and those I drive less frequently. I use

10,000 miles for vehicles out of warranty and over 100,000 miles that I drive frequently. I use Mobil 1. Never had an oil related problem either and the 5 and 10K intervals are VERY easy to remember.

Matt