High mileage oil question

Their "tests" are high-school quality at best.

Oil analysis numbers for wear byproducts and oil endurance (things like TBN). Read the forums on bobistheoilguy.com for enough sample results to glaze your eyes over..

OJ really is innocent too.

Sorry but that's not true. There are many cases of high mileage engines starting to leak after changing to synthetic. One very simple reason is that they synthetic tends to clean out all the deposited goo that is keeping some older engines from leaking. Another reason is the compound/type of seals used in older engines.

The best advice for someone who's been using dino oil in an older engine and changing it as needed is to keep using dino oil and keep changing it as needed.

Maybe I misunderstood the comment, but it sounded like they were implying that if one doesn't drive a cab, one can't possibly understand the test.

No, S. Bigelow nailed it: CR ran a bunch of oils in NYC taxicabs and came to the conclusion that all oils are the same and equally adequate in ordinary passenger car service.

DS

It's supposed to prove the difference or lack thereof between how the various types of oils prevent wear. Your idea won't work because it doesn't have any known starting point. 50k can wear different engines differently. The way they did it was to start with engines built as identically as possible, used as identically as possible and see how they wore over time with the only difference being the oil.

Many? How many is many? 1 in 100? 1 in 1000? 1 in 10,000? The odds are heavily in his favor.

Another myth- "goo helps seals work better." Besides, if he's got a

135k-mile engine with no leaks and no consumption, he was using a good enough dino oil that there isn't any REAL goo in the engine, let alone the mythical "goo" that makes seals work better.

Well, if you are talking about the 1940s, then MAYBE. There isn't a single seal in my 1966 engine that is incompatible with synthetic lubricants.

Not BAD advice. But if he wants added wear protection then a good way to get it is with synthetic oil.

The flaw in the CR test is that its only going to catch GROSS wear that could be detected by micrometers meauring engine parts after tear-down, and that just isn't going to happen with *any* reasonably good oil in a mere 50k miles, provided the engine didn't have a flaw.

In contrast, an oil ANALYSIS can reveal the total concentration and the ratios of the various metals being shed inside the engine when only micro-grams of metal are being lost. It can give a decent estimate of how well the oil is working in just a single 3000 mile oil change, and an excellent assesment if tracked over 50,000 miles worth of oil changes. It can clue you in to damage occuring from something non oil-related, such as a high silica content from a missing oil breather filter or air cleaner allowing dirt into the engine. Or antifreeze contaminating the oil. This would be a particularly good test of the oils when comparing different oils in identical engines because some engine designs shed more metals than others naturally. Of course, CR wouldn't dare do this since a) the fact that oil does matter is contrary to what they wanted to prove, and b) just sending some oil off to Blackstone doesn't seem nearly as scien-terrific in print as staging their own elaborate, yet meaningless, "experiment."

Based on the conversions I've personally seen or discussed directly with the owner/oil changer, 20%. If you want to take the risk, have fun. But don;t tell people there's no risk.

Haven't been inside many engines, have you ?

Really ? It's amazing that they built your 1966 to be compatible with oils that weren't even in use yet.

Under 50K I'd say switch. Over 50K I've seen issues. There's no way I'd switch a 15 year old car with 135K on it.

It might be a bit less hyperbole to say that there are anecdotal tales of engines beginning to leak after swapping to synth. Some of these may even be true.

Or try a different synth, or a synth blend, or a few capfuls of Marvel Mystery at every oil change.

And on other cars, barely broken in. Even as far back as the mid-60's and definitely today.

Rather than believe Consumer Distorts, I just look in the manufacterers factory service manual that states categorically that although the engine does need break in driving practices it doesn't need special break in oil and can use a full synth right from the showroom floor if desired.

Right, if you see above, I mentioned the CR test. Seems like a perfectly good test.

But the question is whether there's any benefit to using synths.

I don't know that they didn't do oil analysis. As I mentioned, it's been a while since I read the report.

And it is. For taxi cabs! Hence my previous (tongue in cheek) question about you driving taxi in NYC.

Donno about where you live, but the benefit where I live is that the engine lasts *much* longer with synthetic oil.

I don't know if this is true everywhere, but in Alaska the Department of Defense has been using synthetics /exclusively/ for something like 35-40 years.

Good guess, Danny Boy, but I'm not Amsoil pusher ... nor even fan.

The API? those overpaid bureaucrats couldn't even come up with a functional definition of the word"synthetic" as it relates to lubricants. And, of course, the API is interested in pleasing the EPA than approving top quality formulations.

You can take their overpriced approval as law if you want to. me? I'll take extra barrier wear adds in my oils. If I have to replace my catalytic converter at 120,000 miles, that's OK. Better that then my motor. Besides, here in the Northeast, it'll be rusted apart by that time anyway.

--- Bror Jace

Doc, Steve is right. The Consumer Reports test was HIGHLY flawed. Type of engine, type of driving, short duration, etc ... and by now it's dated. All oils have been reformulated several times since then.

What I'd like to see is about 20 or 30 Briggs & Stratton engines tortured to death using a handful of different oils. Which would last the longest? Not a perfect test ... but the results would be interesting to pour over. >:^D

For the record, as long as the interval is kept modest (3,500-4,500 miles for most cars, depending on sump size and about a couple dozen other criteria) I have seen little difference between synthetics and mineral-based oils in preventing wear. What seems to make the biggest difference is the additive package.

For example Mobil 1 SJ Tri-Synthetic seemed to be "just OK" in preventing wear while some of the newer and/or more specialized mineral oils (Schaeffer, Pennzoil, Chevron, Castrol GTX, etc ...) have turned in some incredible used oil samples showing incredibly low metal particle counts.

As was suggested, go to the Bobistheoilguy.com bulletin board and look at (literally) hundreds of UOAs (Used Oil Analyses) and see the trends. Might even document them on a spreadsheet. The biggest problem you'll encounter is data overload. >;^)

--- Bror Jace

For what is it worth I have heard there may be other advantages to synth oil than simple wear. I know a guy who used to race cars and got a sponsorship from mobil 1 for a little while. He of course took good care of his car and changed the oil in it about every 5 hundred miles. He didn't mention anything about wear but he did notice

his oil temperature droped by about 25 DEGREES CELCIUS.

I'm no MechE but I'd wager there are a lot of parts(seals, gaskets, bearings) that would last a lot longer if they dealt with lower temps over time

The answer is, you haven't a prayer of getting a good answer from Consumer Distorts.

My service guy keeps telling me not really with a 90 day 3kmile change interval, but he does admit that for super high or super low temps some of the synths may be better, except that with a good change interval not so anyone would notice. However, he does admit that they may offer better gas mileage.