Electric Vehicle Forums - Oil additive as part of dealer service????

I just had the 5000 mile service done on my TCH at the Southern California dealership where I bought it and noticed an entry on my receipt that says "oil additive". I called the service department later in the day and asked what this was and the guy described it as an additive that helps keep the oil from breaking down as quickly since oil changes are done on 5000 mile intervals.

Now this may be reasonable, but I've always been a little sketchy on additives, especially in terms of voiding vehicle warranties. I asked the guy if this was per Toyota specifications and he said it was. This may seem like a dumb question to ask a dealership service department, but I had my reason .... they were going to put in 5w-30 oil until I grilled the "service advisor" so much that he went and discovered that the actual oil cap has 0w-20/5w-20 printed right on it. This didn't fill me with a lot of confidence, especially when he said that their service techs would make note of this requirement.

I did get my 5w-20 oil, but has anyone else had the dealer put an oil additive in as part of the service? I've searched some posts and the consensus seems to be that oil additives are useless. I'm OK with that, just as long as it won't hurt anything. I think I'll try another dealership for future service visits.