I kinda wish they did  a 20/50 for my BSA projects and I’m still wanting to use Castrol in them. I’m pretty sure ROTELLA 15/40 will be just fine in the BSAs. As far as changing to different weight of oil  at different times of the year, I wouldn’t. Pick a good oil in the proper weight and stick with it. Every builder I ever talked to said the same. I just want one brand & weight of oil for all my singles , a couple of jugs on the shelf not a bunch of different brands. Todays oils are great but cannot recommend changing weights just cause it’s cold out.

For my motorcycles - the "5W", "10W, "15W" is of no concern.  That rating is established at 0c/32f and I am never going to be starting my motorcycle at that temperature.  For the temperatures I ride at the difference in force required to start a cold engine is negligible.  For my cars it is a different story, as I do drive my cars in the winter and our weather forecast for next week drops below zero!

The higher 30/40/50 number does have a meaning to me - I mostly run 40 weight oil and use either Rotella 15W-40......as 5W-40 likely has more additives to keep the oil flowing at lower temperatures....and I don't need those additives taking up space in my oil.  I never use 30 weight oil in my air cooled motorcycles....once the riding season arrives I often ride at temperatures over 90 degrees (summer).

Good question.  The Shell website, product description, nor brochure disclose their proprietary concoction.  

This 3rd party independent analysis by the Petroleum Quality Institute of America conducted in 2021 indicates 1,130ppm of ZDDP. Other good information on the ingredients.  Link to analysis below.

https://pqia.org/shell-rotella-t4-sae-15w-40-heavy-duty-diesel-engine-oil/

There are other anecdotal comments on "Bob is the Oil Guy" that supposedly quote emails from Shell indicating that the amount of ZDDP hasn't changed.

I'd use up your 5 gallon bucket - "Good to the last drop". (wait...that's a Maxwell House coffee jingle).  Of course, someone will say that oil goes bad after 5 years or the expiration date.  I've never had an extra container of oil for more than a year, so I have no clue.  While some of the reasoning as to how it can go bad makes sense, if you keep it properly stored in a good sealed container, I'd suspect 5 years is on the conservative side and they just want to sell you more fresh oil.

I use Rotella T4 (Dino oil) most of the time, and if found and on sale I also use ….cal , but it’s hard to find.  Both have good levels of ZDDP.  I use T4 because of price, because I change my oil when it begins to get dirty.  It’s the carbon/grit/etc that the oil collects as it moves through the engine, and that causes most/a lot of the wear, and clogging things.  Our filters are barely adequate.  Clarity begins to leave my oil in the 1500-2000 mile range, and by 2500 it’s cloudy.  If it’s cloudy then Im circulating particles that cause wear.  So I change it.
T-6 is great but it costs more.  When does your oil begin to turn color and go cloudy ?   The oil molecules may still be good based upon milage but the junk they pick up and carry around is not.  Do you still want to continue using it ?  I don’t.

The mileage claims are ridiculous!  Change your darn oil!

It’s easy to like Rotella T4 when it’s $15.98/gallon at Walmart.  Essentially enough for 2 oil changes.

I’m with you Lancer and Dave.  I’m a frequent oil changer about every 1,000 miles (filter every other oil change).  It bothers me to look in the window and see cloudy or dark oil.  It’s so rewarding to see that nice golden oil through the window.

I did recently buy a gallon of T6 on sale for $23 at Walmart.  That’s going in the Shadow at next oil change and I’ll probably still change it at 1500 miles.  I do think synthetic is superior oil based on the molecules.  It cleans better in my opinion.  Compare color to Dino juice at the same mileage and the synthetic will be darker.  To me that means it’s collecting more crap.  My comparison is based on my F-150 at 4,000 miles.

A friend of mine who works with Shell aviation lubes used some shell tool to see what is covering the bike. (Though I do not claim to know how the algorithm works). The oils he came up with when I asked about Rotella equivalent in Europe was not Rimula (though he too said it's very much the same, with slightly different additive package), but Shell 4T AX7,
You will get the details here, with specs PDF:
https://www.shell.com/motorist/find-the-right-oil.html

He checked the additive package for me (perks of being high up in the lubes foodchain) and said that it had high level of ZDDP, though again, I do not know how much... See the certificate of analysis below.

Pricewise it's a good 25% more than Rimula, so you get a 4L can instead of the Rimulas 5L can for the same amount of coin. But then again, it's synthetic, while Rimula is mineral.

Zoltan, all

I think perhaps this oil from Castrol may fit the ticket. I have no experience with it, my bike is still dismantled. It may affect clutch operation, again, I don't know.

It is called Castrol Revival V67SL
This is what they say about it: (sounds compelling, no?)

Classic mineral 10w/40 motor oil with reduced viscosity and increased camshaft wear protection.  Zinc content 2200 ppm.  Suitable for hydraulic valve lifters.

This oil has been developed to meet the problem of the wear protection effect of engine oils on classic engines and racing engines with flat cam followers.

On each rotation of the cam, the oil film will be pushed away for a short moment between the cam and the cam follower.  Anti-wear additives in the oil must here form a protective surface that prevents erosion of the metal surfaces of the cam and cam follower.  The wear problem increases with increasing pressure on the cam followers - i.e. the sharper the cam, the larger the valves, the harder the valve springs, the greater the pressure and the more wear - i.e. the problem is greatest on large V8 engines as well as on racing engines and other tuned engines.

The problem is greatest on relatively high-performance engines and on pushrod engines with mechanical valve lifters, but also occurs on engines with hydraulic valve lifters and overhead camshafts.  On more modern engines, the problem is eliminated through different valve arrangements, different material selection and lower pressure on the valve lifters.

Some of the anti-wear additives are gathered in a carefully composed package of zinc, phosphorus and sulfur compounds that reduce friction and wear.  The package is often referred to as ZDDP.

Due to contamination of catalysts, API lowered the maximum permitted content of ZDDP in API classified motor oils years ago – this effectively covers all available motor oils on the European market.

The content of anti-wear additives in Castrol Classic oils is right up to the limit set by API, while modern fuel-saving oils are far below.

To reduce wear on the camshafts, we have developed 'Revival V67SL²', which is a modified classic mineral 10w/40 oil with an increased content of the anti-wear additives.  The content of the anti-wear additives has thus been brought up to par with the most durable motor oils from the 60s and 70s.

Due to the high content of anti-wear additives, the oil cannot be classified according to the API rules.  Under no circumstances must it be used in an engine with a catalytic converter.

Specifications: SAE 10w/40

SAE 10w/40