Are there any oil additives that when used in a normally functioning engine will prolong the engines life?
I don’t think so. Regular oil changes seem to be key, and in some cases of sludging engines, using a quality synthetic works well to mitigate issues. On the other hand, my vehicles are doing well with 5K oil changes and proper maintenance per the owner’s manual. One vehicle has exceeded 250K miles and two others are close behind. No use of oil additives to get there.
Charlie; the additives already in the oil make the car last its full design life! The SECRET is to change that oil on time, so those additives do not get depleted, and the contamination in the oil does not cause excessive wear.
Whenever a person turns 100 years of age they are always asked what their secret was. Aside from chosing ancestors with good genes, most just led normal clean lives! The same is true for your car.
Modern oils are great. They don’t need any help, in fact in my opinion you are more likley to cause problems by adding “addatives” than just following the instructions in the owner’s manual.
We very seldom see a modern car that has worn out prior to at least 300,000 miles. Very few cars wear out engines. Most cars die due to accident or lack of recommended maintenance.
Back in the 50’s life was different, but today you don’t need fuel or oil addaitives. If you want your car to last a long time, just follow the maintenance instructions in the owner’s manual.
One exception however. I do recommend chaning (not flush) an automatic transmission every 20 - 40,000 miles. Don’t wait unit it starts having problems, that is too late. Change the oil with dropping the pan and cleaning the filter.
Live long an prosper.