F1technical.net

I was wondering...

If oil gets thinner (i.e. less viscosity) over time, will it allow an engine to produce more power due to less resistance?

Or does oil actually get thicker and the reverse is true?

I do not know if oil thickens or thins out as it ages. It does not matter. Motor oil and especially the additives undergo thermal and mechanical degradation. That means that eventually they will fail, and you will have metal to metal contact.
Oil is the lifeblood of an engine, and you have to make sure it is good enough to provide reliable lubrication.
Old oil is bad oil, no matter if it may provide a small improvement in performance, it just isn't worth the risk of destroying an engine.
Anyways, just watch any respectable team, they always use brand new oil, and change it all out regularly. If old oil was able to give a small performance boost, you would see teams filtering and re-using it. They don't, instead they pick the best viscosity andd type of oil to suit their needs, and use new oil, and change it frequently. I suggest you do the same.

I thought that oil doesn't degrade as long as you keep it within it's temp limits? I know they have additives, but if it doesn't degrade if you don't overheat it you could reuse it again right? After a good filtering of course. Or am I being my usual stupid self?

whats the oil number they use in f1 engine?
i mean my car is 15/30

adam2007 wrote:whats the oil number they use in f1 engine?
i mean my car is 15/30

Probably something as thin as water. Looking at the state of some of the used oil that I see, I'd say it's thicker as one of its jobs is to collect all of the crap that accumulates as well as cooling and lubricating.

do you guys use a zero weight Russ?

I've actually never seen a 15/30 before... is that a European thing?

Ray wrote:I thought that oil doesn't degrade as long as you keep it within it's temp limits? I know they have additives, but if it doesn't degrade if you don't overheat it you could reuse it again right? After a good filtering of course. Or am I being my usual stupid self?

Not stupid ray, you're fundamentally correct. But when oil is inside an engine, how can you guarantee the oil does not pass through a location where it overheats? Not a lot, but just a bit of degradation. Oil flows all over the cylinder head, and if some collects on top of a combustion chamber, some of it may have overheated.
Even more important, oil collects particles. Some of the larger chunks are collected by the filter, but a lot of microscopic particles remain in suspension. Media in an engine's primary filters pull out particles as small as 25 to 30 microns (a human hair is 67 microns in diameters). Secondary filters do better — down to 5 or 10 microns — but also add restriction to the flow. But what size particle can damage an engine? One micron particles can wear out things like pistons, rings, and bearings at an accelerated rate.
What's the investment in an engine, even better yet, a high performance engine where some bloke has laboured and poured his heart and soul into building a killer engine for the car he loves. What does a few cans of oil cost? It it worth the risk?
Bottom line, change your oil, don't be cheap or silly.

Well I myself would not put filtered oil back in my truck, much less a racecar. But I do know quite a few people that have never changed their transmission fluid and have had zero problems. How can that be?

Theoretically, old oil would produce more power in a small time window before additive depletion and oxidative thickening overtook any gains.
It wouldn't make sense to look to old oil for power when you could simply use thinner fresh oil.

ISLAMATRON wrote:do you guys use a zero weight Russ?

5/30 fully synthetic is the thinnest we use.

Strange issue this really, cannot see the point in running an old oxidated oil, regardless of theoretical viscosity. Such things can always be adjusted with a fresh lubricant anyway, no?

especially with the new zero weight oils out there

How do the 18 wheelers here in the US get away with running their engine oils for so long? I'ver heard something along the lines of 75k miles. Is that true and if so how?

Ray wrote:How do the 18 wheelers here in the US get away with running their engine oils for so long? I'ver heard something along the lines of 75k miles. Is that true and if so how?

high oil capacity? plus they burn alot off and just add more... but 75K seems extreme, I'm gonna ask a couple truck mechs I know to find out.

18 wheelers also redline at 1800-2000 rpm. They are actually fairly gentle on their oil.