Oil Pressure

[tacoman]

I have noticed that my oil pressure is a little low. Happened slowly. I have run the Catipiller oil analysis on it about every 4 th oil change. It all looked normal except the oil viscosity was reported as being slightly lower than the reference sample. I was using low cost oil (Chevron 5-30). The was the reference sample was the same. Went to 5-30 Castrol and it seems to have helped. Question how could the oil have been deluited? Only thing I can think of is fuel but from where? Leaking injector? No water, metal or antifreeze in the oil, just low visc. Anyone with the same experience?

 

Tacoman

[88pathoffroad]

Normal breakdown of dino oil under use in an engine will do that, AFAIK.

[hardwaretoad]

Interesting question. I'm not familiar with the Catapillar oil analysis, but I can guess what it entails. By "low" on the viscosity, do you mean lower than 5w? Like 0w? 5-30 gets pretty darn thin viscosity-wise to begin with, the whole idea with running it in the winter. Are you testing new, unused oil, or are you testing it after 3-4k miles when you drain it? It might be a matter of the "low cost" oil ~ probably breaks down faster than the quality stuff resulting in the lower vis rating. Might just be a little too low cost, if you get my drift.

 

You say there's no contamination by other engine fluids ~ is that a visual check or do you have access to a lab analysis? Most contaminants would be easy to see, I'll admit. "Oil & water"...

 

What was your oil pressure before? And now? I mean, has it dropped from 60psi to 10? It might just be a failing oil pump... -thnkboutit-

[mws]

Something to keep in mind: Oil viscosity is not a "constant". There are slight variations from brand to brand, formula to formula, and even batch to batch within a given formula. Maybe you just had a slightly "thinner" batch of oil that time around.

So I wouldn't get too excited with small variations from lot to lot. If it remains a lower than you're comfortable with, try some other brands of oil.

[hardwaretoad]

Ditto on mws' fine reply. I've used Castrol for a couple of decades in all types of imports & all types of engines ~ inline 4's, flat 4's, inline 6's, V6's, flat 6's, rotary's ~ all with excellent results. Sounds like Castrol did your's a little good, personally I'd stay with it. Just stay away from the bargain bin crap no matter what brand you go with & you'll be fine...

Edited March 26, 2005 by hardwaretoad

[oilman]

could be a failing oil pump, or just a bad sensor, or

gasoline will make its way into the oil over time especially in an older engine, this can cause a drop in viscosity. oil analysis is really looking for metal in the oil which could warn of failing bearings, even specifically which bearing depending on what kind of metal. I dont know what you are paying for that analysis, but I think it might be a waste of money. oil analysis is something used on large diesel engines, to warn of impending failures, so that the engine can be rebuilt, before it fails. most often seen on boats, large equipment, and stationary power units, where $5-$10000 dollars to rebuild is a deal compared to $50000-$100000 to replace.

in a car it is usually just easier, cheaper, and wiser to replace with a factory rebuild, rather than have the local garage rebuild it himself.

as far as conventional oil goes like someone said as long as you stay out of the "bargain bin", oil is oil, more money just buys you more time between oil changes. I have run NAPA brand oil in everything I own and maintain, including several diesels, and it does just fine as long as you are religious about changing it.

for cars and small trucks I like 10-40 in the summer spring and fall, and use 5-30 for just a few months in the winter. but if you live in a really hot or cold climate you might want to adjust that. here in maine temps run -10F to 90F over the year

Edited March 26, 2005 by oilman