Oil Discolorization

[Hokiefyd]

I searched on the topic and it returned no results. But I'm sure it's been discussed before.

Two of my vehicles (2007 Chrysler Town & Country and 2007 Toyota Corolla) use the 5W-20 grade of oil. In both, I have Pennzoil Platinum 5W-20, with a Purolator Pure One filter on each (in the correct part number). Both engines have shiny metal dipsticks. Judging only on the oil on the dipstick, the 2,000 mile old oil in our Town & Country (with 22,000 total miles on the engine) looks much darker than the 4,000 mile old oil in the Corolla (with 19,000 total miles on the engine). The 4,000 mile oil in the 'Rolla still looks like new -- a yellowy-golden color. The oil in the van has darkened to a dark maple-syrupy color (but obviously not that viscosity).

I'm not concerned that the oil in the van looks darker than the oil in the Toyota. I've read that the color of the oil doesn't really indicate how effective the oil is in the engine. But I'm curious as to why one engine has clearly discolored the oil more than the other, and at only half the miles. What does the discolorization come from? The van sees more "city" miles than the Toyota does, but I'd say both are relatively close in terms of the type of driving. Both have also seem similar ambient temperatures during this OCI (hot NC summer).

Is it good that my Toyota's oil is still lighter than the stuff in the van? Or is it good that the van's oil has already changed color? Does a darker color indicate more contaminants?

 

[rclint]

I'm by no means an expert, just some thoughts.

I think if anything it would be fuel dilution, and blow by gasses. Not meaning in any way the engine causing the oil to be darker is inferior, just that it is adding more to the oil. This could also be exaggerated by the displacement of the engine.

 

[Hokiefyd]

Thanks for your reply. Perhaps not so coincidentally, the van repeatedly returns about 10% less fuel economy than the on-board computer reports. In most cars I've owned, including former Mopar minivans, the OBC has been dead-on in terms of fuel economy. Perhaps I have a leaky fuel injector.

When would be the best time to pull an oil sample if I suspect fuel dilution? Would driving it for 20 miles before the oil change burn it all off so I wouldn't get it? Should I put it up on ramps and let it sit overnight, and do the oil change in the morning, and pull the sample then? I've never done a used oil analysis on this van, but suspecting that I may have a fuel injector problem, I don't see a better time for it.

Thanks.

 

[Hokiefyd]

Nobody? When would be the best time for me to catch an oil sample if I'm trying to find a problem with fuel dilution? Thanks.

 

[jesbo]

Sample the oil for UOA when you do your next oil change drain. I usually drain when the oil/engine is warm but not super hot. That way the oil is at operating viscosity and will fully drain. Collect your UOA sample mid drain, and cap it off right away.

Darker oil coloration could be due to many things. The engine may be operating much hotter, resulting in some oxidation that darkens the color. Could be due to more blowby or carbon in the combustion chambers that are captured by the oil, resulting in darker color.

 

[ZZman]

I would say more blowby. Some engine are built tighter or things seat better.

 

[Hokiefyd]

Okay thanks. I'm mid-way through this 5,000 mile OCI. I plan to put more 5W-20 PP in next time, and will sample the oil when it comes out, when the oil is warm after a regular drive (nothing special). I'll be sure to report back with the lab analysis (from Blackstone).