Why change the oil?
Team Owner
Joined: Oct 2004
Posts: 27,420
Likes: 64
From: San Clemente CA
Originally Posted by JmpnJckFlsh
Its not just condensation, which is bad enough, but even with modern engines there can be some accumulation of other combustion by-products in the oil pan. These combine with the condensation to make ACIDS which can attack the rod and crankshaft bearing material if allowed to remain and accumulate.
Also the engineer's comment that oil doesn't break down was probably about single viscosity mineral oils. Modern multiviscosity oils do their viscosity change trick due to "ultra long chain" chemical molecules in additive packages. During normal operation, these long chain molecules are "sheared" by the motion of the engine internals becoming shorter and losing their ability to affect the oils viscosity. They are, in effect, "used up".
I can't argue with Dave Hill's assertion that owner's change their oil too often, and GM's oil monitor is probably based on tens of thousands of test hours...but, I can't bring myself to leave it in there once it turns close to opaque brown...it's got to go, and the filter too.
Also the engineer's comment that oil doesn't break down was probably about single viscosity mineral oils. Modern multiviscosity oils do their viscosity change trick due to "ultra long chain" chemical molecules in additive packages. During normal operation, these long chain molecules are "sheared" by the motion of the engine internals becoming shorter and losing their ability to affect the oils viscosity. They are, in effect, "used up".
I can't argue with Dave Hill's assertion that owner's change their oil too often, and GM's oil monitor is probably based on tens of thousands of test hours...but, I can't bring myself to leave it in there once it turns close to opaque brown...it's got to go, and the filter too.
Le Mans Master
Joined: Aug 2004
Posts: 6,412
Likes: 1,295
From: Bluffton, SC
I just spoke to my Corvette tech about this. He feels that the condensation issue is there not because of storage, but too many short trips with a car. There's not enough time for the condensation to burn off. Synthetics, he claims, are better in that they provide more efficient heat diisipation than regular oils.
He also said that the C6 computer will figure drive time and mileage into its calculations and usually come up with an accurate estimate of when your oil should be changed.
I monitor my oil. If it looks dirty, I'll change it. Right now, I'll just wait and see how good the DIC is at estimating oil life.
He also said that the C6 computer will figure drive time and mileage into its calculations and usually come up with an accurate estimate of when your oil should be changed.
I monitor my oil. If it looks dirty, I'll change it. Right now, I'll just wait and see how good the DIC is at estimating oil life.
Le Mans Master
Joined: Nov 2001
Posts: 6,984
Likes: 0
From: Central Coast CA
Originally Posted by StanNH
If it looks dirty, I'll change it.
It is simple, oil does not break down, the additives do. I personally trust the computer as GM spent a lot of time and money developing it and it works. If you race often then change the oil sooner. If you are really ****, then you can spend all the money you want and change the oil every 500 miles. If you believe you can go 10,000 miles between changes, then do it but I would at least change out the oil filter sooner.
I have gone 7,000 miles on a 4 cylinder truck engine with regular oil and lasted around 165,000 before I sold it. Not one engine oil related issue. So I think the synthetic oil in my Z06 can easily go the length of what the DIC tells me to.
