Don't do it unless you like rolling the bones.

I, too, thought that synthetic was the greatest thing since sliced bread until I switched to it in a very nice, dealer-maintained, used 240 which I bought. At 112 Kmi., and after giving me flawless service for about 20 Kmi., I decided that the car was so nice it deserved synthetic oil.

What a mistake! Whenever the oil pressure light started to flicker while I lumped the car around parking lots, I checked everything which could cause such a problem culminating in dropping the oil pan to find an oil delivery tube seal almost puked out of its socket in the block. The seal was hardened and black and since the replacement seals were supple and red in color, I assumed that Volvo had noted the problem and changed the compound of which the seals were made. I plugged in the new seals, filled the motor with synthetic again and thought, what a pain in the ass, but problem solved.

The sweet feeling of success lasted until the oil idiot light started to flicker again in less than 1500 miles. I once again went through the dance involved in opening up the crankcase. And, once again I found the oil delivery tube seal in the block dislodged from its home. Now, this was getting serious so I checked all aspects of the delivery tube connection to the block as if it were part of the space shuttle. After fabricating some gaging and comparing the oil delivery tube socket to a known good block, I found the secondary machining of the block to be defective. I modified a new delivery tube to accommodate the slight boo-boo in the block and, after new main and rod bearings, lived happily ever after. By the way, amazingly, I found nothing wrong with the bearings, but I figured, what the hell, I already had the thing disemboweled.

It was only after I checked the log book for that car and realized that the low speed oil pressure came up lame within 300 miles of switching to synthetic that I held the synthetic as the cause. I have heard about leaking shaft seals when an older engine is switched to synthetic and the oil delivery tube seals are no different. The smaller, tougher molecular strings of synthetic oil must find their way into the interface of the delivery tube seal and the wall of its recess in the block. Then, if Lars was having a bad day on the production line at Volvo and a little nonchalant about punching those holes in the blocks, the seals are puked out when synthetic is used.

Right or wrong, that is why I will never again use synthetic oil in a 240.

Rich