Topic: All weather and 59 degree Fahrenheit oil - wtf?

[Dos]

Hey everyone I’ve got a Cb350f and in the manual it says 10w40 for all weather but 20w50 if over 59 Fahrenheit.

This confuses me because people on here say 20w50 is too thick for a little engine but the manual calls for it but the manual also says 10w40 for all weather so wtf?

I always would rather be safe than sorry and protect the engine as much as possible and in the spring it’s always atleast 50 degrees and the summer can get hot.. So what the heck? So confusing. Is there something in between?

[HondaMan]

15w40 falls in between, and is a recommended oil for the Baby Fours (250/350/400F) in the Spring or Fall, or for short-haul commuter service (less than 10 miles to work, that sort of thing) in the summertime. The 20w50 oil will do the best to protect the Hy-Vo primary chain and will yield the most clutch life possible, but it will also cause the engine to lose about 0.5HP over 15w40 at high RPM on summer days. The difference is in engine longevity: giving up that small amount of HP can make the difference between 20,000 mile and 50,000 mile engine life, in my experience with these bikes.

[jaytee-nz]

Hondaman - I've seen you refer to the CB250 four a few times but I can't find any information on this model at all. Do you have any details about them ?

[Dos]

15w40 falls in between, and is a recommended oil for the Baby Fours (250/350/400F) in the Spring or Fall, or for short-haul commuter service (less than 10 miles to work, that sort of thing) in the summertime. The 20w50 oil will do the best to protect the Hy-Vo primary chain and will yield the most clutch life possible, but it will also cause the engine to lose about 0.5HP over 15w40 at high RPM on summer days. The difference is in engine longevity: giving up that small amount of HP can make the difference between 20,000 mile and 50,000 mile engine life, in my experience with these bikes.

I don’t mind loosing a little horsepower. so if I’m understanding you correctly 20w50 is the best option for the best protection With my 350f Correct? So what would be a good oil in 20w50? I remember you said belray awhile back  does this still hold true?  I’ve just also heard that 20w50 is harder to circulate and may cause damage or something but Is that just wrong? Does belrays 20w50 have the same zinc levels as shell rotella?

[jlh3rd]

internet stories and opinions are just that. The engineers that designed your engine know what it needs to run properly. That's why they give you an owner's manual. Follow it. It says using 20w-50 is recommended, and an expert here supports that.
    Just don't use an energy conserving "car" oil...bad for clutches...

[PeWe]

Motorcycle oil. There are threads here about modern oils.
Red Line is my favourite for some dollars more.

My stock CB750 K2 get Spectro mixed with motorcycle synthetic oil since Spectro HD 20W-50 made the clutch to stick together too much.

[Trevor from Warragul]

I have used Valvoline 20w50 non-synthetic oil in my 350 Four for many years with no issues.

[HondaMan]

Hondaman - I've seen you refer to the CB250 four a few times but I can't find any information on this model at all. Do you have any details about them ?

I sure wish I had one...
The Japanese loved Honda's Fours, but in Japan then (maybe even still today?) there is a very expensive penalty built into the license fee for bikes bigger than 250cc (and back then, another at 350cc, 450cc, 550cc, 650cc and 750cc, hence the typical engine sizes of 325cc, 444cc, 544cc, 736cc, etc.). Sochiro loved his 350F and reportedly felt for his countrymen about it (and they reportedly clamored for it), so they took the Baby Four and installed [even] smaller pistons, and [I am told] smaller yet carbs. It makes 17 BHP and tops out around 80 MPH brand new, so in the USA it wouldn't sell, it was thought, despite its 11,000 RPM redline. American servicemen stationed in Japan thought differently, though, and brought quite a few of those home with them in the 1980s. They show up now and then, usually in poor shape, in swap meets. One rider here in Colorado bought what he thought was a 350F engine for his ailing Baby Four from the big meet in Brighton (about 12 years ago, IIRC): when he went to swap engines he discovered it was actually stamped "CB250F-nnnn" and even wrote about it here. He apparently swapped it in, but left these forums before I could make a date to go see it.