ATF as Diesel Injector Cleaner.

lol, woo im not alone! Boy im glad youre here - was beginning to question my own sanity! J

Thank you for posting the technicalities of why a synthetic oil can be less dense and therefore more likely to get pissed out of worn out old oil seals.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Huw" saying something like:

I've a feeling that the perceived easier leaking of synthetic oil is possibly happening when the engine is cold and the 0W or 5W rating is in effect. At normal running temperature the oil is at the same viscosity as a dino of the same grade and should be no more prone to leaking out than the dino oil. The low temp leaks, like all oil leaks, accumulate and give an overall impression of an engine leaking all the time.

How many times have we seen a very small weep accumulate and spread so as to appear to be much worse than it really is?

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Coyoteboy" saying something like:

Thank f*ck for that. Now I can put away the goat grease.

You seem to be under the impression that a 0w/40 is thinner when cold than when hot. I can assure you that this is not the case. It is more viscous when cold despite a 0w rating.

Huw

Oh jesus do i have to go through this AGAIN? FFS.

If your car runs on 10-40 dino oil and you put in the correct grade (10-40) fully synth it is NOT ANY THINNER OR LESS DENSE AND THEREFORE NOT ANY MORE LIKELY TO LEAK.

Its like talking to a brick wall. Please explain how you managed to extract "the technicalities of why synth is less dense" from my comments about viscosity? You MUST be a troll.

But you shouldnt be using a 0 or 5 rated oil unless your engine manufacturer states that this is the correct grade for your use and environmental conditions. You should use exactly the same grade as you do with dino oil.

You're equating density with viscosity again.

Where? I specifically said density is not linked to viscosity and viscosity is measured by the rate of flow through a fixed size hole. I cant be much more clear that im not, can i? Youre trying to suggest that two same-standard oils have different viscosities, contrary to the standardisation.

A less dense oil can flow out of smaller holes than a more dense oil, despite viscocities being the same.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Huw" saying something like:

Well, if a synth oil of say, 5W, is thicker when cold than a dino oil of

5W when cold, that makes a nonsense of the standards system.

What you wrote above was not what I was saying.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Coyoteboy" saying something like:

Well, quite; but many people bung in a synth oil in the hope and expectation of getting some of the perceived benefits of it.

Youre mistaken, the only reason density would play a part would be the extra force due to gravity that might help to drag the oil through the hole, which has the opposite effect than you suggest. Almost all oils are nigh-on identical densities (go weigh some identical volumes if you dont believe me) so the point is moot point. However, just to point out, go get yourself a a less dense fluid. Sayyyyyyy 10-40 oil. Get yourself some much more dense fluid with a lower viscosity (remembering you claim viscosity is not the key point and density is) - water. Now put them in a container with a tiny hole. Which one will pee out faster? Water. More dense and less viscous - in your world the more dense fluid shouldnt escape as fast due to beign more tightly packed and the viscosity is irrelevant. But clearly its not. Whats more glass is a liquid, just a VERY VERY viscous one. Its also denser than water or oil. Dont see that leaking very fast do you. As you can see, density has no link to viscosity or leak flowrate.

Viscosity is a measure of the resistance to deform in shear (flow) through a hole (leak if you like, again, BY DEFINITION). If density were a major factor in this it would be part of the calculations, it is not. If density were part of this equation (as used by the standards) to determine your oil weights, and as you say a less dense oil were to leak faster, your less dense synthetics would have a lower viscosity rating.

You are totally confusing the fundamentals of fluid dynamics, its a complicated subject and very easy to get the wrong end of the stick.

But you can get all dino oil viscosities and grades in synth, so they should stick the correct one in :) I think a problem is a lot of people stick in a less viscous grade and assume that because its synth it will protect better than the correct grade, then wonder why it doesnt.

I'm not.

I'm going on using synth and semi synth of the same grade. The synth leaked out all over the place. The semi synth didn't. There *is* a difference no matter what the theories may or may not say. It's far more complicated than plain density and viscosity, though.

In fact, to complicate matters further. Selenia 20k 10W-40 is like piss, whereas Halfords / Castrol etc with the same 'grading' are significantly thicker.

So complex i didnt check the SAE rating system (being a smart arse :-), sorry! ) and it uses centisroke kinematic viscosity, not absolute viscosity as i thought (absolute does not include density, tis what i used to work with). However since SAE uses kinematic which includes density as part of the calculation so two same-SAE oils should have the exact same flowrates/leakrates.

J

See my other post but to summarise - the SAE rating is a measure of kinematic viscosity which includes density and absolute viscosity to give flowrate. Flowrate through a hole = leak rate.

I wont argue your anecdotal evidence of yoru selenia as obviously thats your experience. But in my experience, and in theory, thats not the case. All i can say is that the halfrauds oil is not thicker or more viscous, there may be other reasons such as additives but i see no reason as the additives are part of the standards too, as Huw says.

The problem i hear a lot of is people just dropping in a 0-40 or a 5-30 as its in the book next to their car as the alternative to 10-40 dino and when it pees out they blame the synth.

Heres an interesting link

Its based on info from an oil marketing manager but if you read it you'll see that theres no point in making synth oils incompatible with older cars or likely to leak more - tis against good business practice. But as they point out, seal shrink/swell is the major factor and its decided by additives. Possibly the additive content of the synth oil you tried doesnt agree with your cars seals, whereas the additive content used in the halfrauds oil does.

I suppose its possible that your semi/dino oil has had lower quantities of seal-swell preventitives and so the seals swelled and wore, adding synth with more anti-swell additives might have caused the seals to shrink back. In fact thats possibly the most likely answer to the problem, as the fully synth will likely be used in new engines, to extend the life of the engine (seals etc) a higher anti-seal-swell additive content may be added to reduce seal wear .

Either way its nowt to do with viscosity.