Recently put car into VOLVO dealer, for high mileage service & full check up for long runs to Europe over next year.

1988 B200E injection 740 GL Estate with 244,000 miles on clock!
Having great faith in my OVLOV and trying to get the best out of it by getting dealer to do periodical 6 monthly 'major-service' on it, they have filled engine oil with Esso Ultron "Semi-Synthetic" oil, instead of normal "Texaco Havoline Premium" (non-synthetic) engine oil, that car has been used to for last 70,000 miles since car bought 3 years ago.

This may seem extravagant to some of you out there, but there are diplomatic reasons for running an old car, which doubles as a buisiness car as well as for pleasure & anyway its all tax deductable according to my accountants.
Car has always had genuine parts fitted. (I think these parts last up to 4 times longer than pattern copied cheaper ones).

I want this engine to last for at least another 150k miles & oil is religeously changed every 5k miles with a genuine volvo oil filter.
The dealer say's that this newer oil will not affect overall longevity of engine lasting at least for another 150k, However, I know that when these new oils were released 7-10 years before, it was generally thought that only new engines should be started with continued use of these oils, & that to use them for older engines would prove false economy as they will wear engines out quicker that started thier lives on non-synthetic oils.

But what do you long standing Volvo-head experts out there think?
Any comments & suggestions would be most welcome - and Thank You for your time.