Is that an order or do you only follow what's written by the mfg?

They should be the best ones to advise you on what is best for your car.

Do what you want and ignore the manufacturer at your own peril.

I always change my own oil and until recently always used the absolute best, Amsoil synthetic oil. However, because of the cost, I recently changed to using Royal Purple synthetic oil. Having three cars, three golf carts, a diesel tractor that takes 10 quarts of oil, a zero turn mower, an ATV, and several pieces of small engine equipment, Amsoil got too expensive. Royal Purple is a small step below Amsoil in quality, but is still a very high quality product at about 1/3 the price. As far as what an oil change costs, I have no idea since I do it myself. That being said, the cost could vary significantly based on both the quality and quantity of oil as well as the quality of the oil filter. I like to use WIX XP (extended performance) oil filters. Don’t cheap out on inferior quality oil and filters, it will cost you a lot more in the long run.

always have relied on the advice of engineers with engine maintenance experience, and only read the manual for the quantity. . both gas and diesel.

I prefer to listen to the people who engineered the product. Some people think they know better than the manufacturer about what multi-viscosity rating of oil should be used. Never understood the logic of making arbitrary decisions.

I don't know under what constraints the engineer designed, there always are, nor the marketing and legal review the manual went through to minimize legal exposure. The maintenance engineers have to keep the machine going and sees all the constraint issues which the design engineer can't possibly design for within the constraints. . having lived and worked with a family of design and maintenance engineers, with all different types of engines and gears, that's who I listen to. .

but if you think that's arbitrary, then the only possible correct answer is in the manual.

We are talking about cars. The only choices for oil is the API rating (or one of the other similar industry ratings) and the multi-viscosity rating. Engines with variable valve timing mechanics require specific weight oil. Not clear why someone would want to second guess that but do as you want since it is not my problem. Feel free to argue with someone else.

Volvo XC60 Maintenance Schedule

Engine oil Every 10,000-miles or 12 months
Fuel filters Every 40,000-miles
Oil filter Every 10,000-miles or 12 months
Air filter Every 20,000-miles
Coolant Every 10,000-miles
Spark plugs Have them inspected every 70,000-miles
Brake fluid Once a year or 10,000-miles

Filters only job is to filter the oil. Oil breaks down & when this happens oil doesn’t do what it’s suppose to do protect your engine. Think about it when you change your filter does your engine oil amazingly turn clear, I doubt it. Oil breaks down & eventually doesn’t do anything.

It might of been but it’s not the same!

I have to change my synthetic 0w20 oil and filter by time not mileage.

I don't put on that many miles on so according to Toyota it's 7,500 miles or 6 months whichever comes first.

It's sure hard draining all that clean oil out after only 6 months of driving but that's what my manual states.

Short trips are brutal.

Toyota recommends that you have your oil changed every 10,000 miles, but to continue with the 5,000-mile service intervals for fluid top offs, inspections, and tire rotations.

Reading this thread, I realize I have not had a tune-up in about twenty years. Are they still a thing? I also use to get new shocks every couple of years. Also, no longer necessary?

I change the oil every 5,000 miles, and buy new tires and brakes when they wear out. That's it. I don't care what the manual says. When the car has 80,000 miles, I'll buy a new one.