straight 30 or 40

[mjoekingz28]

Let's say I tried some straight grade oil in a motorbike with a shared sump (trans/engine).

Would it shear? Or is it shear stable since there are no viscosity additives?

 

[mjoekingz28]

From a thread two lines down:

"If shear loss is your bottom line, some cheap chevron supreme straight 40 held up better than delo in my V8 ski boat, which usually chews oil up."


Man I need to read all the topics before posting.

 

[Rob_Roy]

A 30 or 40 grade engine oil that meets API Service CF-2 will be very shear stable. CF-2 is for 2 stroke Detroit Diesel service, which is a very demanding application in terms of shear stability.

Does your motorbike have a wet clutch?

 

[Ken2]

Is shearing actually that much problem?

In your hot climate I'd use a synthetic 15W-50 to get better cold oil flow and better hot oil lubrication. And excellent transmission protection.

 

[Mackelroy]

Heat, really does a Number on straight weights, they get thinner and thinner. Running a straight 30 weight in a bike anywhere near 200 degrees, that stuff will drain thinner than water.

The multi vicosity oils, have the thickening molecules and actually hold viscosity better, under severe heat. Atleast thats my finding under actual use.

I ran a straight 30 weight in my VFR in 50 degree weather and maybe saw 170 degree water temps. I ran it 400 miles and drained it, so thin It scared the [censored] out of me.

 

[sunruh]

visual observation dont mean squat.

in my tests, i have proven that a good sae30 will hold up better than most of the 10w40s. 1 exception!

in my tests, exxon superflo sae30 postsed a susvis of 62.8 and the ONLY 10w40 to beat that was Maxima 4Extra 10w40 at 66.8.
fyi, havoline 10w40 was 60.7 and 58.3 in two tests. exxon superflo's own 10w40 was 61.2

as examples

 

[Mackelroy]

I like a little heavier film strength than Pure water.

Most of your testing has been related to how the visocity held up in its own range. With a stright weight theres a HUGE difference, between cold and hot state.

BUt, if a straight 30 weight is thinner than water at 200 degrees, thats not to hard to beat in my book, Ive already seen the effect on cam lobes and thin oil films.

 

[Qwiky]

Viscosty tests at 212 degrees farenheit do not differentiate between straight grade or multigrade oils. They test the viscosity at that temperature.

 

[RC46_Rider]

Food for thought.... The greatest wear in an engine typically takes place at cold start up when the engine is "dry". A thinner oil will flow faster and get lubrication to "remote" places in the engine quicker than a heavy oil. The thickest oil that will run is NOT the best oil for protection at start up, especially if the engine has intermittent use.

If your engine is operated with in specified temperatures, RPM limits and your OCI's are reasonable you are extremely unlikely to have "oil related problems" with almost ANY "reasonable oil". Such being the case, the multi vis oils have a definite advantage. At the end of the day, when EVERYTHING is considered, you probably will see lower wear/longer engine life with a premium multi viscosity oil, especially in intermittent operating and over a wide ambient temp range.

 

[dwendt44]

In the good old days, Harley spec'd straight weight oil according to temperature (outside).
Most Harley oil, nothing else was ever good enough, were heavy.
They had their own numbering system so you couldn't easily translate to a common brand oil. Spark plugs were 'special' too.

BUT, they didn't get many miles on them before wear was obvious. No oil filter (the accessory one wasn't very good anyway), and iron engines with so-so machining tolerances.