265,000 miles on an 04 hemi, and for the past year, I have been having to add first 1/4 quart, and more recently, 1/2 quart every thousand miles. Using 10w30, and a quart of Lucas high mileage. Changing the oil at every 4000 miles. Well, that Lucas said to use 2 quarts in an 8 quart tank, so I did that. No difference. That stuff is expensive, so this last oil change, I decided to drop back to one quart lucas and only change my oil every 5000 miles, instead. Well, I have 1900 miles on this oil change, and it hasn't burned a drop of oil. Whassup with that?
I've had that happen before too the exact same thing. It went back to burning oil on the next oil change though, so watch for that, I got lazy after 4 months of not checking my oil every sunday morning. I got in the car fired it up and got that nice engine noise that tells you it's time to dump some in... because clearly the fancy oil pressure gauge I bought and added was a waste of my time since I apparently don't know how to read it or something. Also, if you think the Lucas is too expensive, just start blending in 10-35 or 10-40. Or go to 10-35 altogether. That's really all the Lucas is doing, is blending in a super high viscosity oil to make yours stickier.
Oh, I still check it every thousand miles. Too old of an engine to not do so. What happened to that eye and cheekbone?
Huh??? New one on me, a used oil analysis will prove differently... Additives do deplete in K miles(not 100s), but won't cause the level to drop noticeably... Oil usage has many variables, at 6000mi my '07 Grand Marquis is still dead on full(I do one year oil changes or 8k mi using synthetic)... I've added a quart or two to my other vehicles in less miles... Where'd it go??? I dunno, they don't leak or smoke... Common issues are leakage past rings and/or valve stem seals, a defective PCV valve can cause usage as well
I guess better words the additives burn off...not evaporate like water. This is why the oil level drops. The more additives in a quart...the less "oil" in a quart.
A certain amount of oil burns off at extended driving temperatures too. If you drive infrequently enough to only put on 8000 miles a year... you probably aren't going to see that happen much.
The '07 Grand Marquis is the "tripper", 95% of the mileage is highway(yeah it sets a lot)... The two that use oil are "around towners" almost exclusively... Oil is seldom at full operating temp... Unless oil temp is running in excess of 240*F, there should not be enough evaporation to notice...
If one wants to broaden their horizons, study up on the oil NOACK Volatility tests(ASTM D-5800)... It's a fairly recent development that defines limits of oil evaporation by weight at 150*C... Not all oils are created equal by a long shot but for the commonly specked 5W-20 oils used in modern engines it must be less than 15%... Heavier grades have a lower NOACK so are better at retaining their mass... Still if oil temp is less than 220F, high NOACK ain't your problem...
Same can be said about comparing a '07 Crown Vic to a '04 Dodge hemi pickup truck. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=28&cad=rja&uact=8&ved=0CFgQFjAHOBQ&url=http%3A%2F%2Fdspace.mit.edu%2Fbitstream%2Fhandle%2F1721.1%2F28293%2F55030522.pdf%3F..&ei=96pIU96UIueL8AGL5oHQAw&usg=AFQjCNGhzAMvgeoqTimcQhhk4lRahkvLqA
Yep, evaporation occurs mostly at idle when the oil pump sees its highest periods of inefficiency. It's caused by insufficient coverage of hot surfaces causing burn-off when the coverage gets too thin. Doesn't matter what the overall temp is when you get hot spots idling at red lights. This is the intent of mixing viscosities to achieve the balance your engine wants. Too high and you start blowing through the rings, too low and you get hot spots. When you get it just right, you get that 1 magic oil change where you don't burn any oil.
