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Has anyone ever run synthetic oil in an L8?

I put it in, and quickly realized that it leaks through gaskets too easily. Nothing wrong with using it... unless you don't like a lot of oil dripping onto your garage floor.

Given that oil changes on collector cars should most commonly be based on time-in-service rather than mileage, the major advantage of synthetic oils is pretty much out the window. Use of synthetic gear oils in transmissions and rear axles might make more sense if you really had your heart set on using them.

A friend of mine switched to synthetic oil for an old car, not a Packard, he had with disturbing results. Synthetic loosened all the sludge and other leavings from years & early use of non detergent oil - result. The junk cloged some crucial oil passages and led to catastrophic engine failure Or so he was told by the engine rebuilders.
I like synthetic oil - use in my modern drivers from new. But I'd only use it in my Packards after a rebuild.

No benefit unless you are going to enter in a demolition derby.

The pointer about detergent oil loosening sludge applies to any motor that hasn't had the pan dropped and cleaned, and the valve chambers cleaned. Detergency also affects the rear main seal. I've seen a number of motors reduced to rebuilds due to this issue.

Non-detergent is better in old worn motors that get limited use because water doesn't emulsify and so corrosion is reduced. Kendall makes a good 30w and Valvoline VV265 can be had via NAPA. Lubriplate also makes non-detergent motors oil. The required rating is SB which is obsolete for motors built after 1962.

Not really concerned with the detergent effect, as far as I am aware most if not all oils these days are a detergent type at least anything you can get at the local parts store. I was mostly concerned with the effect on seals and gaskets (mostly the rope rear main) and leakage and if any negative effects were known. West when you say it leaked through the gaskets are you talking a lot like a quart a day or just a minor slow drip?

Just a side note synthetic oil can be worth power as in about a 15hp increase over conventional oil.

No. The trace less frictional loss from using a low viscosity synthetic in place of a low viscosity conventional oil of the same weight will NOT result in an additional "15 hp" in your side-valve Packard or any other automobile engine.

I use Kendall GT1 10W/30, which is a semi-synthetic, in my '47 Super's 356.

Beware of substituting ad copy, hearsay and Internet bluster for vetted info, SAE results.

OD, post #3 above, sums it well. I might add only that
time in service might be lengthened providing your collector
car engine is never started unless you drive it 18-20 miles
over the open road to prevent the formation of acid, sludge,
carbonic acid.

An old mechanic's test was to place your hand on the bottom,of your sump. If too hot to touch longer'n a second or so, you got your oil hot enough to prevent the preceding.

It mystifies us that so many hobbyists start their engines to show them off, then shut them off after a few minutes and let them sit for weeks. Or think blocking the throttle open for 15-20 minutes in the garage, or driving "a few miles" now and then is good for the engine. No, no, no.

If you're concerned about dry starts, and you should be,
since they account for 80-90% of engine wear, according to McDonnell-Douglas, Continental, and the SAE, install a pre-lube device like that from www.masterlube.net

No additive nor anything in a can or bottle will help.

And you do NOT need ZDDP additive, which only settles on
the bottom of your oilpan. The Kendall oil i use, and this
is true of most other premium motor oils, has the SAME level
of zinc as motor oil in the 1970s, when we never heard all
this zinc scare malarkey.

Zinc levels were raised slightly since then, only to
interfere with catalytic convertor efficiency, and so reduced to their '70s levels.

A couple of vociferous codgers in the CCCA whined about
the rapid wear of the chintzy bronze timing gears in their
1940s Cadillac 346 L-head V-8s, both coincidentally just
being rebuilt, and so of course blamed the motor oil. The
350 Chevy V-8 JimBob hot rod contingent continued
yelling fire in a crowded Internet theater and there you
have it.

A degreed Kendall Oil tech himself owning a high-performance flat cam engine told me he knows the
fellow who produced the "Classic Car Motor Oil" purveyed
by the Indiana region of the 1941 Cadillac Club of America (formerly the CCCA). He dismissed that and his own and other major oil companies offering motor oil with increased zinc:

"If you want to stay in business, you
offer people what they want, or think they need."

Non-detergent 30w is readily available and if the motor is full of sludge and worn it is the better choice for limited use. You have to ask for because most of the time it is sold by the case.

hotrod.com/techarticles/synthetic_vs_mineral_motor_oil/

This is a test done by hot rod magazine in which they replaced the lubricants of the test car (engine oil transmission fluid rear end gear oil)with synthetics put the car on an engine dyno and gained 10.1 Hp and 6.1 ftlbs or torque. This test was done with the same viscosity of oil (20w50 which is not thin by any means I use the same weight in my 5.0 mustang) so a thinned oil can not be sited as the power increase. This is just one of countless tests done over the years to show the increase in performance of synthetics.

I do drive my classics probably more regularly than most I wouldn't say daily but several times a week is not uncommon. So the added millage of the synthetic oil life wouldn't be a bad thing for me. But the biggest reason I want to switch is again for a couple more bonus HP and the main concern was leakage.

There has bee a recent trend in the racing world of high lift mechanical flat tappet cams going bad due to the lower zinc levels in today's oils (which other than diesel oil and racing oil is all ut none). This by no means is at the power, RPM, valve spring pressure level of ANY Packard engine but the problem does exist. When I saw building engines professionally, I saw the results first hand. You might not believe the Hot Rod Jim-bobs but the guy putting tens of thousands of dollars into a 100% aftermarket 540 cubic inch big chief head nitrous drag boat motor is no idiot. Again I could site several articles by reputable sources.

If you would have no gain in durability with higher zinc levels why would oil used in semi trucks, that have engines under tremendous internal conditions and are expected to endure over countless miles still contain some of the highest levels of it? I really doubt that a bunch of truck drivers yelled at the oil industry on the internet till zinc was added back into diesel oil, remember having an engine continue to run is how they make money anything that helps that happen is well received.