synthetic oil for 1970 Eldorado; what grade?

This is poor advice. The extra seal-swelling agents added to "high mileage oil" give a short-term reduction in oil consumption due to worn seals, but in the long run the swollen seals wear even more quickly and oil consumption increases.

Incorrect. It has additives to SWELL seals. This does not "rejuvenate" them.

I guess I just haven't caught up with the times then. The only experiences I have with the overpriced junk was to watch it turn engines into pincushions back a few years ago.

Normal gasket seeps or wet spots that weren't enough to ever drip turned into taps running bad.

If the OP does go for it, I sure would appreciate a follow up in a month to see what happens....

The only time I dared to use it in any of my vehicles was just after a rebuild of my t-case and tranny seals and then I only used a semi-synthetic gear oil because they didn't sell any 'real' gear oil at the local auto stores without the friction modifier that my T-5 sure doesn't require.

Mike

"Daniel J. Stern" wrote:

Maybe an odd question, but I'll ask anyway... how does Mobil 1 act in an engine with the old style felt front main seals? I'd like to run Mobil

1 in my Studebakers but they leak enough with Rotella as it is. Haven't gotten around to getting a neoprene seal installed in a timing cover yet, although if I could ever stick with a car for more than a couple years I might (I thought my '62 hardtop was a keeper, until I fell into a '55 coupe...)

nate

Yeah, well, I'll let the more trusting and gullible types pour gunk into their crankcases and run experiments at their expense. Me, when my engines require new seals, I take the absolutely radical step of...

...repairing the problem rather than masking the symptom.

1) Mobil-1 10w40:

2) The "too much VII causes sludge, so don't use this grade" caution applies to petroleum 10w40 and 10w50 oils, but not synthetics.

DS

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.

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...

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

Next predictably-dumb question, Strauss?