Follow the manufacture of your vehicles recommendations. Or change the oil/filter every 7,500 miles.
Around 5,000 miles with conventional oil and 7,500 with synthetic.
5W30 ....and synthetic or conventional is fine, synthetic is higher cost but lasts much longer between changes so the long term cost about evens out
if you drive normally, mostly highway, and not in dusty conditions then I would recommend you change it every 7,000 miles. If you drive mostly city then every 5,000 miles. I do not recommend you use a synthetic blend. Either use conventional oil or 100% synthetic. With 100% synthetic you can go 8,000 miles.
Oil last forever but oil does get dirty. Synthetic oil like conventional oil does get dirty. You can extend your oil changes slightly if you synthetic oil but no more than two or 3000 miles.
5000 miles
You can if you want , as long as the engine is sound , doesn't burn oil or leak oil I've been using synthetic engine oil in my 1995 Ford Explorer since 2001 , I've noticed that I get a little bit better gas mileage on the highway which saves on the cost of gas but my oil changes cost me more money using synthetic oil and when its - 30 / - 40 I think it helps it start easier in the cold
If you mean how long to go in between oil changes, I think that even under the severest conditions every 2000 miles should be fine.
Acids have the ability to respond actively to temperature changes and pressure changes. So it should be avoided.
5w30 supertech synthetic works great for me and is at a good price any brand as long as its 5w30 will work. do make sure however you use 85w90 synthetic lube in the trans very important and it should be synthetic
Whether changes about every minute while climate changes over a long period of time
I was looking at the 2002 Lincoln LS Owner Guide and it calls for 5W-20 semi synthetic . ( as long as you have no oil leaks , or are using oil , then 5W-20 , 100 % synthetic should be better ) P.S. I'm not a mechanic / technician but I have been using 100 % synthetic in my 1995 Ford Explorer since 2001
Every 3000 miles/5000 Kms or every 3 months. If driving in an especially dusty environment or idling the engine for especially long periods, then change oil more often. If using synthetic oil, longer periods between oil changes are acceptable (check with Dodge or synthetic oil manufacturer for those oil change schedules).