Another XC70 question.... sludging of oil...???

Since sludging is purely a function of infrequent oil changes, you can see the evidence of neglect by removing the oil filler cap and looking both at the bottom of the cap and into the cam tray. You will see the evidence of sludge, varish and carbon build up. In order for oil to sludge it must be hot. Oil temps in excess of 200 degrees F will cause dino oil to smoke and thicken. On daily drivers this usually occurs long after its useful life as a lubricant has expired. Since all engines use some oil, pushing the change interval means that the volume of remaining oil in the crankcase becomes less and less as time goes on. Since there is less oil, its contribution to engine cooling becomes less adequate and the oil runs hotter as the volume decreases, hence the sludge. If the volume gets low enough there is not enough free flowing lubricant to protect the bearing surfaces and the engine seizes.

I've seen high mileage (150K miles +) white motors that get regular synthetic oil changes that look and run as if they were brand new: not a speck of varnish under the cam cover, no deposits on the backs of the valves, no grainy carbon junk in the pcv, no lifter noise; just a perfect example of what regular oil changes with synthetic oil can mean to the longevity of a motor.

Bob

Bob,

Thanks for the (extremely helpful) info..... previous owner bought vehicle at 100,000km, and suspected it was abused/overused by original purchaser. Will check out areas you described... am better armed now...

Kevin

What evidence do you have that more expensive oil is of "better quality" and doesn't just have more advertising?

What evidence do you have that more expensive oil extends service life?

I always use dealer service with ordinary oil or changed my own oil using ordinary oil and never had any service life problems with the engine. This ordinary oil always met the specs that Volvo published.