synthetic oil for 1970 Eldorado; what grade?

I feel there are experts out there, but the information doesn't seem to be readily available....or even difficultly available. We hear a lot of claims and hype, but little or no actual data to back anything up.

Interesting... I've NEVER seen it on ANY store shelf. 0w30, 5w30, 10w30, and 15w50 are always stocked, and sometimes that goofy 5w20 that Ford was/is calling for in some applications. But I've literally never seen Mobil 1 10w40, and I've passed down the oil aisle of a lot of parts stores, too... Of course this may be part of the new Mobil oil line-up, because I see that 15w50 is now only shown as being available in the "Mobil 1 Extended Performance" line, not the "Mobil 1" line.

Synthetic oils sometimes use viscosity modifiers too, it is a myth that they don't. They do normslly require LESS viscosity modifier to achieve a given viscosity range, and in fact Mobil 1 10w30 and 15w50 contained NONE the last time I researched it. But the wider-range oils like 0w30 and 5w30 do contain some (although less than an old hydrocracked 10w30 might have) and its quite likely that a synthetic 10w40 contains less than a hydrocracked 10w30 too. But 10w40 is a pretty useless grade to fool around with when modifier-free 10w30 and 15w50 are available.

There are experts, and it is readily available:

That's the traditional Amsoil line about cleaning up sludge.

Really though, polyalphaolefin tends to harden seals. So assorted ingredients are added to improve seal compatibility, like an ester base. Newer seal materials should be more compatible with PAO.

I believe the initial Mobil 1 formula (PAO only) used to have horrendous seal compatibility problems. I wouldn't worry about the current Mobil 1 with seals made in the past 15 years.

Now if you're talking about the original seals of an early 70's Eldo, that might not be a good idea. They might not take to kindly to being exposed to PAO.

I've also heard that Mobil 1 (and perhaps other synthetics) use a more stable (read more expensive) VI improver, which can be justified due to the high cost.

Oh, you mean self proclaimed internet experts?? What brand of motor oil or filter do any of the motor vehicle manufacturers tell you not to buy?? They recommend on the basis of weight and rating, not opinion...

I've been there before. It is a step in the right direction, but not authoritative information.

Why don't you actually READ the site? Yes, there are opinions thrown back and forth, but people also post the results of their oil analyses that are done by places like Blackstone Labs. That website happens to be one spot where you can see how lots of different oils hold up in lots of different types of vehicles. Yes, opinion is present on that site, but there is far more quantitative analytical data there than I ever see here.

The kind that's not API-approved and the kind that doesn't meet OEM specifications, respectively.

Next predictably-dumb question, Strauss?

With regard to your last sentence.....

Try to be nice! Are you possibly pontificating profusely "on the basis of weight and rating, not opinion..."? How well do you predict? Are you into stock brokering perhaps?

Just an observati> >

If only you would learn to read... I asked what BRAND of motor oil or filter. See if you can Google the answer.

Another case where some hard data would be appreciated, isn't it, Daniel.

We would wish to assume that a company like Castrol would have performed extensive testing, but that may not be true.

Last year, I contacted a number of motor oil manufacturers/compounders asking for hard information. Got sales blurbs back. Pure BS.