SOHC.co.uk Forums > CB750

Which Engine Oil should I use ?

<< < (4/10) > >>

paul G:

--- Quote from: totty on November 28, 2016, 09:32:08 AM ---The oil thread gravitational pull is starting.....

There is a standard for oil for wet clutches so clutch slip is easily avoided http://www.oilspecifications.org/articles/JASO_MA_JASO_MB.php

Gearboxes should also have EP additives to reduce wear, but you rarely see that bit debated, it's always about the clutch because that's where you can feel the difference.

Personally for road bikes I just buy any known brand bike specific oil, yes the prices are a rip off, but it saves having to understand all the oil threads. (for trials where the clutch feel is more important I use Motul 300v)

--- End quote ---

That is the reason to go for the Diesel one as it has additive’s for the turbo.
There has been many, many discussions on here about it and the people who are in the know recommend Diesel not petrol oil.

Trigger:
Paul is correct, you need the right spec which is found in diesel oils for the gear box and clutch. Car gear box's and clutch are separate to the workings of the engine. Make sure the spec recommended in you Manuel fits the spec on the oil you wish to buy.   

K2-K6:
As any aside,  welcome to the forum kew. I'm assuming you're running that motor in an outfit, is that for road racing?

It's something I think that ends up just hanging as no ultimate conclusions are really informative enough to define what the mythical (well they appear mythical to me) friction modifiers are in any observable or verifiable facts.

If I were to pay for and build up an engine I would consider the oil performance in protecting that as a primary aim and then try to see how that could perform for the conditions the clutch is in. I'm not niave enough to dismiss the clutch as being essential that it operates properly and is able to transmit the torque asked of it but it becomes purely speculative if the engine lunches itself when used fully.

I've been looking at many aspects of oil in various engines and can see many parts of those specifications which are published but when you get to the "friction modifiers" that shouldn't be used in wet clutches,  nothing appears available. How can logical decisions be made when this area almost resembles the magic circle?

I'm aware that molybdenum disulfide is considered accumulative in soft clutch materials, and looks detrimental. It's seems as if this is used then in the short term if it made the clutch slip then it wouldn't be removed by changing the oil back to non moly type. So I would try to avoid oils with that ingredient.

Most of the oils specified for use after about 2004 have things like ZDDP removed to avoid contamination of exhaust after treatment devices and reduce the effectiveness of the cats or dpf kit used on cars. I think it's worthwhile avoiding these as the replacement seems to be moly although there is nowhere I can see that will really nail this component down. It's also considered in emissions driven decisions that the removal of ZDDP (primarily used to protect cams in older engines) will result in shorter life of these components. They dismiss this on the basis that they will last long enough and anyway a significant failure after the end of warranty will ultimately lead to a newer and more efficient vehicle being bought. It takes no account of the field we are talking about as they really couldn't care about old engines.

It's hard to get any real hard data about some of the things that concern us, but useful if we can unearth things that would give improved protection.

Greebo:
K2-K6

What bikes do you run [is the clue in your user name ?] also what oil do you use ?

K2-K6:
My name here is from those two 750 models but they are not currently running. I've been looking after things like this since the 1970s when there was much less choice of decent oils when now there are loads.

Right now I have a 1984 cbx750 on the road which I've been running on Mobil 2000 semi synthetic which is a 10w40 oil. This motor has hydraulic valve adjusters, incorporates an oil cooler as standard and also (I think it's maybe the first general production bike with one)  a slipper clutch. That is a car oil but the clutch has no signs of slipping under load and it's a pretty banzai powerband for the age of bike. It takes off about 7000rpm and if you're not quick enough to change up you'll hit the rev limiter at about 11200rpm it first and second. It's output is about 94bhp.

Are you after a recommendation for something or to discuss further?

I do think it's fascinating area to discuss,  but it is coloured by many aspects of oil marketing speak rather than engineering principles.

Just the statement of "friction modifiers" amuses me as the oil in it's entirety is a friction modifier, which is exactly why we use it in engines!

Navigation

[0] Message Index

[#] Next page

[*] Previous page