Now that I have put some miles on the Volvo that I bought in mid-April, I have developed a few questions. It is a 99 V70 non-turbo that I bought with 196,670 miles. After about 1600 local miles, I drove it from Kentucky to northern California, and shortly after my return I drove it New Jersey and back. I now have about 205,750 on it.

According to the paperwork with the car, the oil had been changed at a quickie place with 5W30 Valvoline synthetic about 2000 miles before I got the car at a cost of $81.38. I changed the oil 1000 miles after I got it because the oil was filthy, it was using oil, and the filter was about the size of a shot glass. Since they had the previous owner on a 3000 mile change schedule, and the book cites a 7500 mile interval, I suspect they felt justified to not actually change it every time. There is no way I can back that up, but after I changed it, it was still clean enough at the 3000 mile mark that it was hard to read the stick and the consumption seemed to be reduced. I used 10W30 synthetic and a Mann W917 filter. I changed it again today with the same.

So much for the history. For this change I over shot the 7500 mile mark by about 500 miles, but 7000 miles of that were the highway miles for the two trips with very few heating/cooling cycles. Over the course of the 8000 miles I went through about 4 quarts of oil, so the average is a quart every 2000. But, the usage rate is not consistent. I did not keep careful track while on the trips, but I know that between fill ups there was often little or no difference on the dip stick, and then the next check might show it needed a good bit to bring it to the max.

A couple days ago the oil was about 2 “Xs” above the minimum. I did not add any because I was planning the change. Today I checked it before the change, and it was about 2 “Xs” below the minimum. I think there was less than 100 miles in those couple days. The car was not on completely level ground for these checks, but it was in the same place both times. It was slightly nose low and left side low.

Here is something else I found interesting. The owners manual says it takes 6.1 quarts with filter, and it says there is 1.6 quarts between the min and max marks. After dumping 5 quarts out and putting on a new Mann W917 filter, I added about 6.2 quarts. This brought the oil only to half way (3 Xs) between the min and max marks. At this time I had done my best to find level ground in the driveway.

So, it seems that the dipstick is calling for quite a bit more oil than the book calls for. I know that running too much oil might contribute oil consumption. However, the rapid oil consumption seen in the last few days on the old oil was when it was below the halfway point on the stick, which would have been below 6.1 total quarts.

It is not leaking anywhere I have noticed. Also, I have twice picked up code P0420 for cat efficiency below threshold. After the first time I replaced the rear O2 sensor on the advice of the parts store reading the code based on his observation that the voltage output of the sensor looked wrong, though I did not see the output myself. He owned an S80 himself, so he may have been a cut above the average parts house guy with the code reader. The same code returned in about 3500 miles. I suspect that oil burning is causing a problem with either the O2 sensors or the cat, or both.

Anybody got any ideas about the erratic oil consumption? Any thoughts on the cat efficiency codes being related to the oil consumption? Sorry for being so long winded.

Thanks,
Charley