Summer Oil Weight | GTAMotorcycle.com

Summer Oil Weight

M

Merkid

Well-known member
I had a discussion with an old time biker similar to me.

We got onto a discussion about our air/oil cooled bikes of days past, ie" FJ100's, Ninja 1000's, Suzuki GS1100's etc. and the summer time riding temps that limited our inter-city travels. The factory weight for most of those models was 10W40 however my buddy mentioned that he cooked his FJ motor while coming off the Gardner and getting stuck in TO traffic in one of the hottest days of a summer past. Since that time, he was recommended to bump up the viscosity and use 15W50.

I mentioned that I would be concerned with that oil mix in the cooler riding days of early spring and fall time, especially during a cold start up in my newly acquired '05 Bandit.

What are your thoughts on switching to a synthetic blend of 15W50 for summer riding and whether it would better protect the engine ?
 
Stick with high quality oil in the viscosities recommended by the manufacturer.

I doubt the oil viscosity in your friend's FJ had anything to do with cooking the motor, they were designed to take a lot more heat than anything Toronto could throw at them.

Personally I'm not sold on synthetics in motorcycles either. Synthetic's primary advantage is it's ability to sheer stability -- which is very important for small powerful engines. Thing is small engines also contaminate oil quickly that the primary advantage of extended oil change intervals is generally no realizable because change intervals are tied to contamination -- and that's the same regardless of which oil you use.

I know there are a million opinions on this, mine comes from experience using Rotella T for 40 years. I change oil on the old girls every 5000km, on newer bikes 5-7500km. I've taken many bikes over 100K and in 40 years I have never sufferer an engine related failure.
 
And it won't matter if you bike is stored inside 15 50 will be fine all the time.

Sent from my Chesterfield using my thumbs
 
The service manual for the GSF1200 has the typical Japanese viscosity chart that covers pretty much every multi-grade oil between 10W30 and 20W50. However "Suzuki recommends the use of SAE 10W-40 engine oil" is at the top. Factory oil change interval is 6000km.

I don't have substantial experience with Bandits, but IIRC they are pretty much the pinnacle of air-cooled motors (big oil cooler, lots of actually functional finning, judicious use of internal oil spraying - all developed for the higher strung GSXR1100).

I would be perfectly happy using 10W40 or 15W40 in it. Maybe consult a Bandit forum to see if they say any different
 
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Your Bandit has nice big oil cooler sticking out the front there. You'll be fine.

GSs and FJs don't.
 
I had an '01 and an '05 GSF1200.
I ran 20W50 in them. I sold the 01 with 91,000kms. Buyer wanted a compression / leakdown test before buying.
It came back with numbers equal to a new engine. Sold.
The way a very experienced mechanic explained it to me:
Being thicker, 20W50 takes longer to circulate. Therefore it has more time to cool inside the giant oil cooler up front.
The 05 worked like a champ in 115°F Aug weather down south.
 
Read this study and get back to us. If there's one thing it establishes, it's that 95% of the oils in the test do ALL their jobs adequately. Even the modern conventional oils do a good job. Synthetics are best, though on older bikes there are complaints that they seep past the gaskets because of the smaller molecules. Just go with what your manufacturer states in the user manual, you can't go wrong.

"Thicker oils are more difficult to circulate, especially when an engine is cold, and wear protection may be sacrificed, particularly at start-up. Thicker oils also require more energy to circulate, which negatively affects engine performance and fuel economy. Furthermore, the higher internal resistance of thicker oils tends to increase the operating temperature of the engine. There is no advantage to using an oil that has a greater viscosity than that recommended by the equipment manufacturer."
Click to expand...

 
Gary said:
Being thicker, 20W50 takes longer to circulate. Therefore it has more time to cool inside the giant oil cooler up front.
Click to expand...
I'm not an expert, but an oil pump will only flow a certain amount regardless of viscosity. I seriously doubt hot 20w50 will take longer to flow thru an oil cooler than a lighter oil.
 
Wingboy said:
I'm not an expert, but an oil pump will only flow a certain amount regardless of viscosity. I seriously doubt hot 20w50 will take longer to flow thru an oil cooler than a lighter oil.
Click to expand...
Ok. Same pump. We'll take the extreme route.
System filled with water.
System filled with bitumen.
Same flow?
(I'm not an expert either).
 
The high-viscosity oil will "take longer" if it leads to so much suction on the inlet side of the pump that it makes the pump cavitate, or if it requires so much pressure on the outlet side of the pump that it causes the relief valve to open. If you are within the allowable temperature range specified in the owner's book for a given oil viscosity, neither situation should happen in normal situations. If you are the type to whack the throttle open the instant a cold engine starts and bounce the engine off the rev limiter, stop doing that.
 
Gary said:
Ok. Same pump. We'll take the extreme route.
System filled with water.
System filled with bitumen.
Same flow?
(I'm not an expert either).
Click to expand...
The oil pump is positive displacement meaning 1 turn send the same amount every time no matter what the oil or fluid. The limit would be like Brian said if it cant suck it in or if the relief is being forced open because it as no where to go. Either situation is very bad news cavitation will destroy the pump and a blocked system is not lubricating the engine. But neither of those are going to happen unless you decide to run 220 weight oil or something.

Sent from my Chesterfield using my thumbs
 
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