5-20 oil

Not an urban legend. The synthetic oil, over a short period of time, disolves a lot of what the Dyno oil left behind. If that is all that held the oil in, it WILL leak. And on a Mitsu 3.0, there are LOTS of places to leak oil around thevalve gear in particular - but oil pan gaskets and front seals as well.

So you're saying that there are no technical reasons to use a blend? That the only reason is to incrementally cut the cost of the oil and on the process knowingly dilute some fo the benefits of the synthetic oil?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

I've heard that "dissolves everything" legend as well. I've never seen any real data to back this up, and I've put synthetic in a couple of engines with more than 50K on them with no problems. I think both are urban legends. People make a change and something happens (a leak) and human nature is to imply cause and effect to what is likely just a simple correlation.

Matt

I see too many posts on any given week on the LH car forums where someone has just switched over to synth and now suddenly has serious problems. One or two a year might be coincidence. 2 a week is not coincidence.

I also personally experienced it on a high mileage Subaru that I switched over to synth suddenly. The synth definitely loosened up crap that got into the lifters. The timing of the onset and what I had to do to resolve it proved it (to me) in that one case.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')

Urban legend. "Sludge and varnish" never keep the oil in.

I was really saying that the piston scuffing claim is bogus. Blends are fine, if cost is a driving factor. And to be honest there are blends (and straight non-synthetics) out there now that turn in oil-analysis numbers that are very competitive with pure synthetics. But given that I like to keep cars 10-20 years (or more), I believe that picking a name synthetic and sticking with it gives better long-term assurance of a good oil without constantly hanging around the internet to see how various formulas have changed this week versus last month.

And you are a mechanic??

No I'm not. But I am an engineer.

Why do you presume to think that "sludge and varnish," which form at random and have no structural strength of any significant sort, can actually form a working seal?

I don't know, Steve. I *vividly* remember the one and only time I used a sudden-flush (kerosene commercial-type flush - came in a quart can) on a high mileage engine. It was a 1980 Chebby Citation V-6 - the rear crank seal was the rope-type (not rubber). Before the flush, there were no leaks. Immediately after the flush - and I mean 5 minutes after the flush when fresh oil was put in - I laid under the engine with it running and watched oil streaming out of the rear seal. I have to believe that the interstices of the rope were sealed up with residue, and that residue was dissloved away by the flush. A rubber seal isn't going to have the interstices, but there is that interface between the seal and the shaft. Now - there's no way an intact soft, non-swolled or shrunken rubber seal is going to leak, but I could see a special case where a seal was hard and barely sealing, and a little residue could make the difference between slight seepage, and steady drip or stream leakage.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Figures. Get your hands dirty before you start talking about things you know nothing about.

No presumption at all on my part. 35 years of experience as a mechanic. Have you ever attempted to remove a few years accumulation of sludge and varnish from an engine? It can block up oil galleries so tight that 60PSI of oil pressure cannot force any oil through. And it takes a whole lot more than a toothbrush to remove it. Try a chisel.

OK, I'll admit that I can see how a rope-type seal *might* work that way. But even in that case, my hunch is that the "quick flush" spoo probably attacked the seal directly, not any embedded gunk in it.

I don't know you, so I won't brag that I've been inside 5 times as many engines as you have. So why do you ASSume you've been inside more engines than I have? Or that I never "get my hands dirty." I'm not a mechanic, but I've been a car hobbyist for over 20 years.

Have you ever actually removed that kind of baked-and-burned in place material (I'd hardly call it 'sludge' or 'varnish' at that point) from a SEAL? I haven't. Yeah, I've chipped it off the bottom of intake manifolds where the exhaust crossover shield had dropped off, picked it out of valve springs that have been overheated until they're blue and limp, and chiseled it off of heads that were warped from overheating or had been starved for rocker and valve oiling by clogged pusrhods (Ford)... but I don't think I've ever removed anything from a SEAL that you couldn't wipe off with a Q-tip and kerosene.

Bill made a good point about rope-type seals being a different animal, and so are old-style cork/neoprene matrix gaskets. I'll readily admit those might theoretically be aided by gunk plugging the pores. But a), I've switched engines with rope seals and cork/neoprene matrix gaskets to synthetic without them gushing or even leaking, and b) those are hardly common items in any engine anybody's going to be dealing with on a regular basis today. I'm more likely to see them working on an old flathead 6 or 60s v8 than people with an engine that might call for 5W20 oil.

Because this is the very stuff of usenet:-

- assumptions

- making bold (and bald) statements grounded in the shifting sands of supposition and vague recollection

- being all-knowing

- rudeness (incl swearing and offensiveness).

But one can still get decent info and have civilised discussions.

DAS

For direct contact replace nospam with schmetterling

Couldn't have been that the flushing brew ruined a seal or two... No, that could never happen...

Matt

You mean talking about things like you do?

Lots of presumption on your part!

That hardly makes you an expert on oil seal design and function.

A seal and a plug are two different things entirely. You can stuff a brand new crank seal into and oil passage and likely block it completely. Likewise, an oil drain plug doesn't make a very good crankshaft seal, yet it plugs the hole in the oil pan very effectively. Two totally different concepts. I'll grant you that sludge can make an effective plug, but it doesn't make an effective seal against a rotating component.

Matt

Nor would it ever happen that residue/"gunk" embedded in the seal was dissolved away? I could easily picture semi-liquid/semi flexible residue, over time, slightly displacing the seal where it met the crankshaft, and then when dissolved/washed away by the flush, there is a nice new gap between seal and shaft that previously was filled with the residue without doing much at all to the seal itself.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Yes - called static and dynamic seals.

If it's the right consistency, it would - like a gummy sludge that builds up being closer to a solid as you move through the seal/shaft interface from inside the engine to outside - takes years to form.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Your hunch is wrong. And it's not just rope seals. Ever seen cracked neoprene gaskets? Not being a mechanic, you likely have not - but trustme, they harden up and crack with age. As long as there is a good film of varnish/crud covering the cracks and the joints between the gasket and the engine parts, little if any oil gets out. Wash away that film, and you have oil sneeking out everywhere. Same thing happens with paper type and cork gaskets as they dry out. Same thing happens with neoprene lip type seals, and specific to the Mitsubishi engines, the rubber cam plugs. A dirty high miler 3.0 Mitsu is virtually guaranteed to leak oil from the rocker gaskets, cam plugs, and camchaft seals if switched to synthetic or flushed without replacing those seals and gaskets. Good chance of rear main and front main seals as well, but not nearly as common as the top end.

I've been a hobbyist for 38 years, and a mechanic for 25 of those years. I've owned and worked on cars aged from 1928 on up. I've rebuilt engines, resealed engines, and repaired engines on vehicles from Moscavitch to Rolls, in the northern and southern hemispheres, and on both sides of the atlantic. Doesn't matter what kind of car, or where it is driven, if not properly services, they ALL varnish and sludge.

Gaskets are seals too. And no, I have not bothered to remove that kind of crud from shaft seals - but I've replaced seals that had ample evidence and accumulation of crud on them that were in bad enough shape they would have been leaking a WHOLE LOT if they had been clean. Not only that, but enough varnish build-up on the shafts themselves to form a "second lip" that the seal ran against .

And 5W20 is not the only synthetic oil in use today.