question about thin weight oil
08-09-04, 10:17 AM
#26
Mountain Rotary Mod
Join Date: Nov 2003
Location: Freaking Poland!!
Posts: 2,411
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Dokta
Can you please be more specific? The additives that are used to modify the viscosity on multigrade oils are different for polyalpha olefin based oils and polyol ester based oils. These additives are all long polymer chains, and as far as I knew, the only downside to using them was shear strength loss. This was due to shear forces actually breaking the long polymers into shorter molecular chains, or when the polymers would align themselves to create a path of least resistance.
I have read in other places that it is bad to used 10W40 and 0W50 oil in rotaries, but I havent gotten a good answer as to why. And just like the "synthetic is bad for rotaries" argument, I refuse to believe it unless I understand exactly what is going on.
I have read in other places that it is bad to used 10W40 and 0W50 oil in rotaries, but I havent gotten a good answer as to why. And just like the "synthetic is bad for rotaries" argument, I refuse to believe it unless I understand exactly what is going on.
Lower weight oils are usually not recommended for rotary engines because of the e-shaft and all of the bearings. Low weight oils at the temperatures the engine runs will be too then to provide adequate protection between the bearings and the e-shaft. As anyone can tell you, once the e-shaft goes the engine goes.
The additives that you mention that are used to "thicken" light weight oils gives you the same problem as the synthetic oils, it will not burn clean and will leave residues and deposits on the rotor housings.
Now, if you're running 2cycle oil in the gas (like I am) you CAN use synthetic oil since you no longer have to worry about oil needing to burn. Of course, I would still never use a light oil because of the e-shaft and bearings.
08-09-04, 12:54 PM
#27
Full Member
Join Date: Apr 2004
Location: Hartford, CT
Posts: 188
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Parastie
Rotary engines pump oil directly into the combustion chamber to lubricate the apex seals. Oil in the combustion chamber MUST burn or risk damage to the apex seals. Synthetic oils are (usually) designed to not burn inside of an engine and survive much higher heats the non-synthetic oils and will leave deposits on the inside of the rotor housings leading to damage of the apex seals.
Lower weight oils are usually not recommended for rotary engines because of the e-shaft and all of the bearings. Low weight oils at the temperatures the engine runs will be too then to provide adequate protection between the bearings and the e-shaft. As anyone can tell you, once the e-shaft goes the engine goes.
The additives that you mention that are used to "thicken" light weight oils gives you the same problem as the synthetic oils, it will not burn clean and will leave residues and deposits on the rotor housings.
Now, if you're running 2cycle oil in the gas (like I am) you CAN use synthetic oil since you no longer have to worry about oil needing to burn. Of course, I would still never use a light oil because of the e-shaft and bearings.
Lower weight oils are usually not recommended for rotary engines because of the e-shaft and all of the bearings. Low weight oils at the temperatures the engine runs will be too then to provide adequate protection between the bearings and the e-shaft. As anyone can tell you, once the e-shaft goes the engine goes.
The additives that you mention that are used to "thicken" light weight oils gives you the same problem as the synthetic oils, it will not burn clean and will leave residues and deposits on the rotor housings.
Now, if you're running 2cycle oil in the gas (like I am) you CAN use synthetic oil since you no longer have to worry about oil needing to burn. Of course, I would still never use a light oil because of the e-shaft and bearings.
08-09-04, 11:36 PM
#28
Eats, Sleeps, Dreams Rotary
iTrader: (1)
Join Date: Jun 2001
Location: London, Ontario, Canada
Posts: 3,106
Likes: 0
Received 0 Likes
on
0 Posts
Correct me if I'm wrong, but Icemark has posted that information before regarding conventional 10W40s leaving extra junk behind due to the specific polymers required to make that oil.
As for using a 5Wxx being bad, got anything to back that up? I know that the engine sounds smoother on startup with it. My thinking was that the engines I've had have sounded a tad rough on startup with 10W30 in cold->cool weather and 20W50 in cool->hot weather. Everyone knows the first 30 seconds of startup cause the most wear on typical engines because the oil is thick and perhaps not everywhere yet. Due to the higher year of a rotary a 5Wxx oil should thicken up quickly. Shouldn't a 5W50 be at 30 before a 20W50 is at 40? Also, synthetics are typically more effective at low temps.
As for using a 5Wxx being bad, got anything to back that up? I know that the engine sounds smoother on startup with it. My thinking was that the engines I've had have sounded a tad rough on startup with 10W30 in cold->cool weather and 20W50 in cool->hot weather. Everyone knows the first 30 seconds of startup cause the most wear on typical engines because the oil is thick and perhaps not everywhere yet. Due to the higher year of a rotary a 5Wxx oil should thicken up quickly. Shouldn't a 5W50 be at 30 before a 20W50 is at 40? Also, synthetics are typically more effective at low temps.
08-10-04, 12:11 AM
#29
Former Moderator. RIP Icemark.
As posted countless times:
as far as my sources for the lower base stock viscosity weights having issues (in all high reving motors, not just rotarys):
Toyota's TSB on 10W40 and 10W50 oils, and why they didn't outright say it, They suggested that customers using 10W40 and 10W50 oils in any Toyota/Lexus DOHC engine should have their warrenties questioned, and there will be sludge build up and high wear issues.
GM's complete outright suggestion to its dealers that the use of wrong weight oils such as 10W40 and 10W50 in any GM car (built after 1990) would void the warrenty for the same reasons as Toyota (sludge and deposit build up and wear).
And of course the VTR page on everything you wanted to know about oil: http://www.vtr.org/maintain/oil-overview.html
Remember with a conventional oil, a 10W40 or 10W50 uses a 10 Weight base stock, and long chain polymers that "unwind" to make the oil work like a 50 Weight when warm.
There are a considerably high amount of those polymers when using the low weight base stock over a middle weight base stock (such as a 20W50, which uses a 20W- considerably higher).
And shear strength alone is enough to stay away from a conventional 10W40 in any high reving motor. The parts tolerances typically do not tolerate any loss of film... something that happens when the long chain polymers rip apart.
Aside from even the shear issues... why would you want an oil with an increased polymer additive level than you need???
as far as my sources for the lower base stock viscosity weights having issues (in all high reving motors, not just rotarys):
Toyota's TSB on 10W40 and 10W50 oils, and why they didn't outright say it, They suggested that customers using 10W40 and 10W50 oils in any Toyota/Lexus DOHC engine should have their warrenties questioned, and there will be sludge build up and high wear issues.
GM's complete outright suggestion to its dealers that the use of wrong weight oils such as 10W40 and 10W50 in any GM car (built after 1990) would void the warrenty for the same reasons as Toyota (sludge and deposit build up and wear).
And of course the VTR page on everything you wanted to know about oil: http://www.vtr.org/maintain/oil-overview.html
Remember with a conventional oil, a 10W40 or 10W50 uses a 10 Weight base stock, and long chain polymers that "unwind" to make the oil work like a 50 Weight when warm.
There are a considerably high amount of those polymers when using the low weight base stock over a middle weight base stock (such as a 20W50, which uses a 20W- considerably higher).
And shear strength alone is enough to stay away from a conventional 10W40 in any high reving motor. The parts tolerances typically do not tolerate any loss of film... something that happens when the long chain polymers rip apart.
Aside from even the shear issues... why would you want an oil with an increased polymer additive level than you need???
08-10-04, 03:24 PM
#30
Eats, Sleeps, Dreams Rotary
iTrader: (1)
Join Date: Jun 2001
Location: London, Ontario, Canada
Posts: 3,106
Likes: 0
Received 0 Likes
on
0 Posts
I still don't see any reason to not use a synthetic 5W50. If anything again reading the link you've posted, I'm more convinced than ever and the VI ratings confirm what I said above.
Thread
Thread Starter
Forum
Replies
Last Post