Why does consumption increase the longer oil in use?

Not open for further replies.
Jun 11, 2002
Fort Smith, AR
I have a 95 Club Wagon with a 5.8L engine. I've noticed that the engine consumes more oil the longer it is left in service. When the oil is fresh, the engine uses none for the 1st 1,000 miles. A couple of ounces the 2nd 1,000 miles. Upto a 1/2 quart the 3rd thou. And from 4-4,750 miles recently, it used a full quart. Seems to follow the same pattern regardless of brand, or type of driving. Why is this?
A couple possibilities: a) the oil may be thinning with use, shearing to a thinner viscosity or being diluted with fuel and being burned b) the oil is getting dirty and not ring sealing as well as new oil Have you done a UOA at the end of an OCI?
I make this point to people whom I coach on car maintenance. Funny thing is, when I was a young boy of 14-15 (25yr ago) my Greaser cousin-in-law made this point to me and further explained that when you find yourself adding oil often, it's time for a change. I could have been even younger, and possibly this is my earliest memory of an oil issue. (sniff) I also remember the Kendall of my uncle and Grandpa Clark's Rislone (c.1976). The whys include about everything you can imagine like increased friction from contaminates and all the aforementioned causes.
[Off Topic!] While we are talking about the good old days and oil consuption I have one for you. I can remember when it was normaly for new cars to use some oil dureing breakin. It was normal for the car to not burn a drop and then all of a sudden it would use 1/3-1 quart in what seemed like over night. Once it did this you knew the engine was broken in. It would not use any more fo r a long time. All of my recent new purchases have been consuption free even dureing break in.
I did a uoa on this engine about 10K miles ago using Penn HM 5W30 for 3,500 miles. Fuel dilution, insolubles and viscosity were all within normal parameters. However, that sample may have been helped by an AutoRX treatment I did on the van about 7K before the uoa was taken. At that time Blackstone suggested I stretch the duration out to 4,500 miles. You might be right Pablo...time to do another.
John, my Audi S4 used oil for the first 10k or so. About 1 1/2 qts in the 1st 7500 miles, then about 1 qt in the next 5k. Ever since, it's used less than 1/2 qt every 5k which is my usual OCI. so I rarely add anything. 130k on her now.
Not open for further replies.