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Another Oil Weight Question....


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Yes I know all about the lycoming additive vs camguard as that topic has been beat to death in Mooneyspace. I live in Las Vegas where we see 110F days and on the runways even hotter. Ive been using 20w-50 in the winter, as temps warmed up in the spring 80w+ and with summer temps over 100F I switched to 100w+. The problem I am seeing is the thicker oil is causing very high oil temps. I am in the green but on the up end of that. Talking with Philips at OSH they recommend I go back to the 20w-50 Victory even with these summer temps that I am routinely in to help get more oil through the cooler. I have gone through all my baffling, sealed everything and even went through with a pick and made sure all radiator fins are getting the max air flow. Been having to fly with cowl flaps open to keeps the temps at bay. Is 20w-50 safe for these high OATs and lowering the oil temps as well? 

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Thicker oil is more viscous so it will lead to higher temps.  Thinner oil is less so and thus lower temps.  The same applies to oil pressure which is also important.  So going to a thinner oil is going to more than likely reduce your temps a bit as well as your oil pressure.  

You can search for a happy medium but green is green whether it is the top or the bottom.  You are in Vegas which is an extreme environment in the summer.  I would expect needing to keep cowl flaps open in an environment like that where you are so far off from ISA.  

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We see very similar temp here in DFW. I run Phillips Victory 20w50 year round - with CamGuard (my preference for cam). My oil temps are really good. I do monitor my cylinder temps to keep them 395° or lower. Cowl Flap as needed for that.

My oil cooler is fairly new and the baffles are top notch (thanks to @Sabremech).

-Don

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As mentioned, 20W-50 and 100W+ are the same viscosity spec, SAE 50, once at running temperature.    I'm in the Phoenix area and generally switch between Philips X/C 20W-50 in the winter, in case I go somewhere cold, and Aeroshell 100W or 100W+ in the summer.   Sometime the oil changes work out that there's a fair amount of overlap, so I'll have 20W-50 in when it's hot out or 100W when it's "cold" by our standards.

The main difference I notice is that the Philips X/C 20W-50 will set off the oil pressure alarms on my JPI far more often than the 100W does, both on the high and low sides.   Very often I'll get the high oil pressure warning on takeoff, even if oil temp is in the green, and it'll disappear after a minute or so.   If I do a go-around after a long descent, I'll get a momentary high pressure warning.   When I pull off the runway at idle I'll sometimes get a low pressure warning if the oil has stayed hot.

I rarely get any of those warnings with the Aeroshell.   It's weird, but there's definitely a difference in behavior between the two oils.

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2 hours ago, EricJ said:

As mentioned, 20W-50 and 100W+ are the same viscosity spec, SAE 50, once at running temperature.    I'm in the Phoenix area and generally switch between Philips X/C 20W-50 in the winter, in case I go somewhere cold, and Aeroshell 100W or 100W+ in the summer.   Sometime the oil changes work out that there's a fair amount of overlap, so I'll have 20W-50 in when it's hot out or 100W when it's "cold" by our standards.

The main difference I notice is that the Philips X/C 20W-50 will set off the oil pressure alarms on my JPI far more often than the 100W does, both on the high and low sides.   Very often I'll get the high oil pressure warning on takeoff, even if oil temp is in the green, and it'll disappear after a minute or so.   If I do a go-around after a long descent, I'll get a momentary high pressure warning.   When I pull off the runway at idle I'll sometimes get a low pressure warning if the oil has stayed hot.

I rarely get any of those warnings with the Aeroshell.   It's weird, but there's definitely a difference in behavior between the two oils.

Do you notice any difference in consumption? My oil consumption went down when I switched from W100 to 20W50. I've heard others with the opposite experience.

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1 minute ago, PT20J said:

Do you notice any difference in consumption? My oil consumption went down when I switched from W100 to 20W50. I've heard others with the opposite experience.

I have a spreadsheet with all my oil additions and oil changes, and there doesn't seem to be any significant or consistent difference, but perhaps an occassional benefit to a few changes with 100W+ that had lower consumption.    I'm about fifteen hours in to my summer switch to 100W+, so we'll see how this one goes.

 

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12 minutes ago, PT20J said:

Do you notice any difference in consumption? My oil consumption went down when I switched from W100 to 20W50. I've heard others with the opposite experience.

Oil consumption aside from drastic changes is a fallacy in GA.  They are lawnmower engines they burn/leak oil.  Mike Busch has numerous videos on this.  Even an engine burning a quart an hour can be a safe/good engine it generally just has leaking rings (not advocating but it is also not the sign of the apocalypse). 
 
Temps and PSI in the green with reasonable and consistent consumption is the key.  My F will burn more or less oil than yours but it is going to be in the wheelhouse and it is consistent in what it does. 
 
Going back to the original poster comparing summer in LAS where it is exceptionally over ISA to other folks who are closer to ISA is an exercise in apples and oranges.  Of course you are going to have temp issues, you are at the extreme end of the spectrum. 

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Supposedly the theory behind mu;lti-vis oil getting lower oil consumption is that the viscosity index improvers continue to thicken the oil when it hits the hot cylinder walls causing a better ring seal. So, if the oil is getting past the rings it may help, if it's going out the breather, then probably not.

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