Sent an oil sample (Mobil1-10W30) to Blackstone Labs and got the report back, via e-mail today. There was only 2,524 miles on the oil, (132,700 miles on car) but it looked really dark, which is why an analysis was done. This was not the first time Mobil 1 was used.

The oil report stated "this was a 5W/30 diesel-use engine oil." What does that mean, I poured it out of Mobil 1 10W30 containers to put it in the car. I bought them at Costco.

My big concern - the fuel percentage showed up as 2.3%, which slightly sheared down the weight to a 57.4 SUS Viscosity@210F,(should be 59-68) and the insolubles were 0.5%, which may indicate continued cleaning of internals.

None of my other cars (3) ever had any fuel in the oil on past analyses.

I would appreciate any recommendation on what to look for. Oxygen sensor? Leaky injector(s)? Regina engine management system?

The car does not use any observable oil. What do I check first.

If anyone is interested I will post the whole oil report, let me know.

Plugs, Distributor cap and wires were changed out 1,500 miles previously.

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92-944, 94-944, 97-960 - Amsoil lubes throughout,, K & N air filters, Silverstar headlights, Green Diamond Tires

Diagnosis from my certified Volvo/Mercedes technician of 35+ years experience: "Bad Oxygen Sensor". On the earlier cars (this is a 92') a slowly failing (130K+ miles)will not set a code. The aging sensor cannot keep up with quickly changing engine management functions, and so the extra rich condition, as evidenced by slowly decreasing gas mileage, and the oil test results.

With a new oxygen sensor installed the car runs great. The gas mileage is back up, maybe even better than the last 50K.

The fuel pressure regulator was fine.

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92-944, 94-944, 97-960 - Amsoil lubes throughout,, Silverstar headlights, Green Diamond Tires

P.S. the newer cars with the latest engine management systems will "set a code" if the oxygen sensor is out of specs. by as little as 2.5%.
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92-944, 94-944, 97-960 - Amsoil lubes throughout,, Silverstar headlights, Green Diamond Tires

Look for a rich engine condition: old oxygen sensor, ECT sensor failing, fuel pressure regulator dying, something of that sort.

BTW, I hope they sent you the correct report.

If you use Mobil 1 consistently, you should have good reports.