Oil question (no not the usual!)

[Guest]

Hi again folks.

I know the engine oil question has been beaten to death many times, but i am curious about the "original" Suzuki recommendation for the first GS bikes?

I have owned my 78 GS750 since 1983. When i first got the bike, i bought a Haynes manual so this manual is not so much younger than the bike. It says to use 20-50 engine oil, and the update at the back of the manual that covers up to 83, makes no different recommendation.

I seem to recall that when the GS series first came out in the mid 70's, plain "20-50" engine oil was recommended for just about everything!

But on the oil filler cap on my 78 GS, it states in cast in lettering to use SAE 10-40 oil!

I am just curious here? Was there an early change by Suzuki? Does the genuine early owners hand books state 20-50? If so, whats the reasoning behind this "quick" change?

According to the well reasoned info in this article posted on the GSR, 20-50 would have been better suited to our bikes? (then)

http://www.calsci.com/motorcycleinfo/Oils1.html

10-40's would be better for cold starting, but does this really apply that much in our all roller bearing crank engines? I would have though that at least with the oil specs of the time, the higher temperature factor at the "50" end of the equation would have been better for these high performance (for the time) air cooled engines?

Anyone got any thoughts?

Footy.

[Nessism]

Suzuki spec'ed 10W-40 for general usage on most all GS bikes. The manual states when 10W-40 is not available, other grades are allowable (the manual has a chart showing different oils weights and the applicable temperature range). 20W-50 is allowable when the temperature is above 14F (which strikes me as pretty low).

[Footy.]

Suzuki spec'ed 10W-40 for general usage on most all GS bikes. The manual states when 10W-40 is not available, other grades are allowable (the manual has a chart showing different oils weights and the applicable temperature range). 20W-50 is allowable when the temperature is above 14F (which strikes me as pretty low).

So it is the info in the Haynes manual that is incomplete.

Thanks for the reply.

Footy.

[Steve]

Here is a clip from the official Suzuki 850 manual: (I find it interesting that 10w-40 isn't even included)



Yes, many of us have roller-bearing engines, but that is only on the lower end. The cams still ride in plain surfaces.
If the oil is too thick when starting, the cam bearings may suffer for lack of lubrication.


.

[Nessism]

Here is a clip from the official Suzuki 850 manual: (I find it interesting that 10w-40 isn't even included)



Yes, many of us have roller-bearing engines, but that is only on the lower end. The cams still ride in plain surfaces.
If the oil is too thick when starting, the cam bearings may suffer for lack of lubrication.


.

550 factory manual is the same. Basically they are saying use 10W-40, but in a pinch you can use those other grades per the applicable temperature range.

[Footy.]

Here is a clip from the official Suzuki 850 manual: (I find it interesting that 10w-40 isn't even included)



Yes, many of us have roller-bearing engines, but that is only on the lower end. The cams still ride in plain surfaces.
If the oil is too thick when starting, the cam bearings may suffer for lack of lubrication.


.

Yes i agree that the cam bearings are probably the most vunerable area in cold starting in early GS engines.

But, our cam bearing surfaces are "fully grooved" because of the low pressure lubrication system, allowing a greater availability of oil over a larger area. In theory, i would think that high pressure oil systems offer more resistence to initial start up oil flow, because of the restricted oil flow through bearings that allows the higher oil pressure to develope.

In this case i think we are getting oil to where it is needed quicker, and so we could stand a slightly thicker oil on cold start up than high pressure systems?

Footy.