how often should the oil be changed, and what kind of oil should be used in a 2000 mustang, with 120,000+ miles
I change at 3000 mostly and use regular Mobil 5000 in my 500K Buick, my 180K Olds, and my 12K Acura. Also use it in my lawn mower.
Use the oil recommended in the owner’s manual and change at the frequency recommended in the maintenance schedule that came with the car.
There’s no need for “special” oil as a vehicle ages.
I’m going to play devil’s advocate here and disagree.
At 120,000 miles, the car that the Owner’s Manual describes no longer exists. The engine’s clearances, compression, are not what the vehicle’s engineers specified (or prehaps even fully within “service” limits), the amount of blow-by the oil has to endure has risen, etc. This can have an effect on the vehicle such that a different viscosity and/or drain schedule is optimal. (Rule of thumb: higher viscosity and shorter drain interval.)
In a similar manner, an aged engine w/ a bit of carbon can require higher octane than the manual specifies (hot spots and such).
Meanjoe makes some good technical points, but if the engine is running well and not brning excessive oil I’d still recommend using the periodicity and oil recommended in the owner’s manual, although I admit that I personally don’t like to go past 5,000 miles between changes for those cars that recommend longer intervals.
I’ve yet to see an owner’s manual that tells you to change oil type or increase oil change frequency after a certain mileage, and engines with 250,000 - 300,000 miles are common.
I don’t think most engines’ service limits have been reached at only 120K miles. I would not want to own such an engine.
so is it ok to wait until 5,000 miles or is 3,000 better
Fresher is always better. However, if you check your owners’ manual I suspect you’ll see 5,000 miles or more.
NOTE: I recommend against taking it to fast-lube chain shops for this. Find a reputable independent shop. Fast-lube chains cause way too many problems. The oil changers are often poorly trained kids who know little about cars and are pushed to do the job as fast as possible. This forum is repleat with stories of stripped drain plugs, oil not refilled, tranny fluid drained and oil overfilled, and all manner of problems from quickie-lube places.
As long as the vehicle is not using excessive oil between changes, I would stay with the same oil and schedule that car has always had. If it works, why change? If this is a new vehicle to you and you don’t know its past history, start with the recommended oil and keep an eye on it.
I am going to guess that the recommended oil is 5w30. Try it. Check the owners manual for the schedule, but if the schedule hasn’t been maintained in the past, the oil will get very dark, very fast. I don’t mean a dark carmel color but a deep brown to black color. If that happens, change it again. Sometimes you have to do two or three oil changes a few hundred to a few thousand miles apart to make up for the sins of the previous owner. Its worth doing though.
If the oil consumption is high, you might switch to 10w30.
I’m still using the oil I started using when I bought my 98 Pathfinder back in 98…Now has 345k miles (daughter brought it home this past weekend). And still use the same interval (5k miles)…Still doesn’t burn one drop of oil either.