I'm not so sure. Today, there are plenty of excellent products. I've used BelRay gearbox lube in my KTM 380EXC and it is no better or different than 10W30 motor oil. In fact, it says something to that affect on the bottle!
Redline gear lube does perform differently, as does Amsoil. Probably due to the synthetic nature of those.
As for 2 stroke oils, there are, in my opinion, far better oils today. Ones that won't gum up power valves and so on.
I'm one of the few people who went through gallons of MC1 and MC1+ in my street legal 2 strokes. I'd have to say that the performance of that oil was less than perfect. I started mixing it 50-50 with "cheap" Castrol, (not castor) generic 2 stroke oil and got better results.
The best overall 2 stroke oil I've used was Mobil 1, MX2t and/or Castrol TTs (TTs being still available)
As far as 4 stroke engine oil, it's clear there are conventional products that are very robust and work well in many applications. A favorite of mine is Mobil 1, 10W-40 MX4t (racing motorcycle oil, with high ZDDP and a true Group IV base stock) also TDT 5W-40 Turbo Diesel Truck and, of course, M1's 15W-50.
Cool, I guess I should elaborate...
I'm talking 4 stroke stuff suitable for Harley Big Twins.
I used to run BelRay full synthetic (EXS I think) in my Sport bikes and it made a significant difference in shift quality and clutch feel. It was a long time ago though... So of course it came to mind when I wanted to improve transmission performance and clutch feel. There seems to be little talk of BelRay here.
I'm trying to sort through the whole same oil for all three holes / different oil for all three holes issue, and I'd like to decrease the drag in the clutch (yes I've done the adjustment procedure) when cold in particular and make N a little easier to hit. Seems Harley has flopped on the suitability of SYN3 in primary case although some dealers still use it. Also, BelRay is carried by the dealer, so I doubt they would give me any warranty grief over it, in the unlikely event the warranty was needed.
BelRay seems to be one of the few that list a Syn as suitable for primary. Mobil appears to say M1 Vtwin is suitable and of course Amsoil and Redline appear to recommend a Syn for the primary. (Incidentally, I've had a similar good experience with Redline MTL in a car)
This is not so much about syn/non-syn but performance/availibility, this seems to be a highly charged issue.
i tested EXL 20w50 and found it to be.....lacking
flash of 410 was good
susvis of 81.9 after 2.9 hrs is pretty weak
add pack has nothing impressive
it ran fine, shifted fine and wear metals were fine, but for just "fine" it is expensive!
I think Red Line is worth a try. I like it in my bike; another air-cooled twin with a separate sump. Use the regular 20w-50 (you don't need the motorcycle-specific stuff) in the crankcase, Shockproof Heavy in the transmission, and 75w-90 for the primary.
When I was a kid, I used Belray (simply because they had stickers). I fouled a lot of plugs on it and didn't care for it. I liked Yamalube 2R. I think Belray decided to spend more on advertisement and less on actual oil research. I have to agree, better oils out there. Castrol TTS is the best modern oil, I have found.
I ran Bel-Ray Synthetique in my ZX600C for about the first 42,000 miles. 15W50 IIRC.
I still had a perfectly functioning 2nd gear long after most of my friends' FZRs and Katanas were gone.
Compression across all 4 cylinders was still good at 42,000.
I switched to Castrol GTX 20W50 at about that time. Started having to hold the bike in 2nd about 20,000 miles later and lost 2nd gear about 10,000 after that. Compression was still good at 93,000 miles but the transmission was trashed.
I cannot absolutely credit the Bel-Ray for the condition of my transmission at 42,000, but I sincerely believe that my bike was in better condition than most everyone else's 600 at that time because I used a good quality oil.
It was my only vehicle. When I wasn't working or sleeping, (or maintaining my 3000 mile OCI) I was riding. 20,000 miles + a year was normal
Sunruh, is it because you had a bad experience with GTX, that your don't recommend it? Alot of people use that oil and I haven't seen any posts about motor damage by anyone that uses it. I used it 30+ years ago in my bikes and never had an issue.,,
while it did not blow/lock up my motor.
it did it no favors either.
worst susvis start to end change of all my tests.
worst wear metals produced of all my tests.
great oils dont shear
good oils will barely shear into the next grade.
gtx went from a 50 to a 30.
imho, not worth picking off the shelf to put in a shopping cart to pay for.
you could pick worse i guess..water or milk or orange juice for your crankcase.