Oil change and additives

I change the oil in my volvo and my wifes lexus about every 8 to 10,000 miles.I use mobile 1 extended performance oil in both.

my question is do i need to add an additive (lucas oil treatment.)at each oil change. at the present time i do.my volvo has 163,000 miles on it and the lexus has 108,000.am i wasteing my money???

Why are you using an additive? Are you experiencing any problems? If not, quit using additives. The Mobil 1 extended oil that you use is already complete.

Agree; you don’t need those additves. I would keep using Mobil 1, but change oil a little more often. Try 7000 miles for both cars.

I think your intervals are fine.

I would sooner take a dump in my crankcase than put an oil additive in a healthy engine.

  "I would sooner take a dump in my crankcase than put an oil additive in a healthy engine".

Wow, that presents a VERY vivid image!!

Especially Lucas…

How many bars of EXLAX would THAT take?

Forget the additives. Depending on your type of driving I’d change the oil more often; especially if it involves a lot of short hop, stop and go driving.
For some people, going 3 or 4k miles is too long.

Could that be defined as blowby?