What oil "clings" best to an infrequently run engine?
- Thread starter Zack1978
- Start date
Carlostrece
$100 Site Donor 2025
A thicker viscosity will leave more film longer. However, a thicker viscosity takes longer to flow and get oil pressure at cold start. So both thicker and thinner have their advantages and disadvantages. Therefore I think it's best to just use the normal recommended viscosity for the engine and climate.
Synthetic oil would slightly be better (than conventional) because synthetic usually has less evaporation. So its film should last longer. Also, synthetic flows faster at cold start. So you'd get faster oil pressure ar cold start.
So I suggest using a synthetic of normal recommended viscosity for your engine and climate. Any brand is fine. I'd prefer Pennzoil syn if I wanted the best and don't care about cost, but I use Valvoline syn because it's more than good enough and costs way less. However, any brand is acceptable. You can continue using Supertech.
P.S. - The thing that clings the longest is the oil additives. The additives cling indefinitely. So a good additive package is very helpful. That said, don't all oils have good additive packages these days?
Synthetic oil would slightly be better (than conventional) because synthetic usually has less evaporation. So its film should last longer. Also, synthetic flows faster at cold start. So you'd get faster oil pressure ar cold start.
So I suggest using a synthetic of normal recommended viscosity for your engine and climate. Any brand is fine. I'd prefer Pennzoil syn if I wanted the best and don't care about cost, but I use Valvoline syn because it's more than good enough and costs way less. However, any brand is acceptable. You can continue using Supertech.
P.S. - The thing that clings the longest is the oil additives. The additives cling indefinitely. So a good additive package is very helpful. That said, don't all oils have good additive packages these days?
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Something an engine sees when sitting is condensation. I'd trust a group III/III+ synthetic, with a lower ambient temp viscosity, more than a group II conventional when it comes to dealing with moisture, especially with a non-detergent oil as there's nothing there to slow or prevent rapid oxidation should water be present. Thus, I'd want base oils that are naturally more resistant to oxidation. Oxidized and dirty oil will be less effective at preventing rust.
Another factor is evaporation, as mentioned above, but not in the sense of rust. Realistically, even very light conventional base oil like Nexbase 3030 would have little to no evaporation at ambient temperature. The issue is altitude. When you're 15,000 ft high, air pressure is -45% less than at sea level. Lower air pressure means volatility increases. (This is also why avgas has very high lower distillation points compared to other gasoline blends.) This is why you don't see a 0W-30 aviation oil as the need for light base oils to meet that winter grade would make the oil too volatile at high altitude. Somebody like HPL could probably make a 0W-30 that's less volatile than that P66 goo, but they'd be the only ones crazy enough to attempt it.
Higher cylinder head temps would, once again, favor synthetic base oil. Synthetic will take the heat better.
It's possible the reason conventional is still favored in aviation oil is simply due to customer opinion or theory. Companies (especially the majors) produce products that will sell, not necessarily what works best. Even if P66 found much better results with a group III synthetic, the fact that 95% of their customers (in that realm) think synthetic sucks means they're more likely to use a conventional base oil, that they know is inferior, because it's what will sell. Then because the company keeps making only conventional, that further validates the myth that conventional is better, and that pile of bull manure gets bigger and bigger.
Another factor is evaporation, as mentioned above, but not in the sense of rust. Realistically, even very light conventional base oil like Nexbase 3030 would have little to no evaporation at ambient temperature. The issue is altitude. When you're 15,000 ft high, air pressure is -45% less than at sea level. Lower air pressure means volatility increases. (This is also why avgas has very high lower distillation points compared to other gasoline blends.) This is why you don't see a 0W-30 aviation oil as the need for light base oils to meet that winter grade would make the oil too volatile at high altitude. Somebody like HPL could probably make a 0W-30 that's less volatile than that P66 goo, but they'd be the only ones crazy enough to attempt it.
Higher cylinder head temps would, once again, favor synthetic base oil. Synthetic will take the heat better.
It's possible the reason conventional is still favored in aviation oil is simply due to customer opinion or theory. Companies (especially the majors) produce products that will sell, not necessarily what works best. Even if P66 found much better results with a group III synthetic, the fact that 95% of their customers (in that realm) think synthetic sucks means they're more likely to use a conventional base oil, that they know is inferior, because it's what will sell. Then because the company keeps making only conventional, that further validates the myth that conventional is better, and that pile of bull manure gets bigger and bigger.
Fresh oil.
I've brought back to active service a fair number of motorcycles that had been parked for a long time. Some decades long. The only storage damage I've ever seen is first gasoline related; varnish, rust in the gas tank. Second, rust inside the cylinder. Not a surface normally protected by oil. The inside of the rest of the engine is almost always fine.
SammyChevelleTypeS3
$50 site donor 2023
#1) Many do not know or will not accept the facts about condensation. Especially when setting up any engines for the storage. Just like a lot of folks argue "how/why can I have condensation in my gas tank when I have it sealed up?" Well , just like "rust never sleeps" which is 100% true, condensation is all around us all the time. Gets into places one would least expect.
#2) Companies sell what people will buy. LoL It has often been said that fishing lure makers , developed and sold lots of baits designed to "catch fisherman and not really the fish."
There are many things folks can / should do when they store engines or vehicles to prevent issues when put back into use. I myself have stored and resurrected a few with minimal issues. All of them were stored inside garage or shops.
SammyChevelleTypeS3
$50 site donor 2023
STP was fined as mentioned. DuraLube that I fell for in the early 80s was found to be near 100% simple 5w30 motor oil. Slick50 was found to be more "slick" than anything close to special.
I wonder about this a lot. Mobil AV-1 was an aviation PAO based synthetic developed 40 years ago that was pulled off the market because, as I understand it, it wasn’t dealing well with lead in some continental engines. Mobil AV-1 History . Perhaps more problematic than it’s formulation alone, it was launched with the claim of 200 hour oil change intervals, as opposed to the 50 hours common with traditional group ii base ashless dispersant airplane oils.
A group III with proper add pack would seem like a great idea for airplanes but I think the market is too niche, with limited sales, the bias you referenced as a result of AV-1 fallout, and rife with legal/liability issues. As a result mostly group II and one 50/50 PAO blend, as best I can tell all formulated 40+ years ago, are what’s used today (and constrained somewhat by mil specs and government certification requirements).
Furthermore the one global source of approved TEL (lead) for aviation fuel, Innospec in the UK, has recenly stated they won’t be making it anymore after 2030, so formulating an oil that needs to deal with lead might seem like wasted effort at this point. No more lead by 2030 . The recently approved 100 octane unleaded alternative, GAMI 100UL has been getting bad press lately for fuel leaks and paint destruction though. Which is to say while I welcome the removal of lead I’m not looking forward to the fuel system problems that will inevitably occur during the teething phase of the switch.
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Yeah, " slick" in their marketing and" slick " in relieving people's wallets of money ! The process of bonding teflon to metal sure doesn't happen from pouring a room temperature liquid ( with no metal surface prep or chemical primer/ binder adhered to the metal surface) into an engine crankcase and then operating the engine. Otherwise the cookware manufacturers have been doing it wrong for all these years.
In a prior role, I supported many household name companies who buy lots of large Cummins-powered generators for data centers.
Really smart people working for Google/Microsoft/Apple/Meta/Amazon couldn't grasp the idea that condensation is inevitable when you have a 9 tons of steel and cast iron heating and cooling MUCH more slowly than ambient temperatures. Water Vapor passes effortlessly through crankcase vents and air intake filters. The residual soot inside the engine's hot side is a magnet for moisture and will cause those components to rust.
They wanted to have both utmost reliability and no run time (emissions). So absurdly insistent on not running the engines were they that they were willing to spend lots of man hours on engine inspections, even disassembling part of the engine to do so! They eventually accepted my assertion that taking things apart is entirely counterproductive if reliability demonstration is the goal (the old "if it ain't broke, fix it until it is").
They wanted a quick and easy way to assure constant engine readiness without doing what was required-- coolant heaters, constant prelube, continuous fuel circulation/filtering, and regular LOADED generator runs to get the oil hot and refresh the oil films.
And yes, engine internals that are nominally oil-wetted WILL rust under some conditions of disuse. Didn't think it was possible until I saw it myself. Oil films do not prevent rust indefinitely. With long enough drainage and enough condensation cycles, your preservative effect is gone and your critical surfaces will rust.
MolaKule
Staff member
I agree that the "synthetic-bad, Group II good," myth has been perpetuated throughout the industry as an incorrect cause-and-effect relationship.
We have shown it was the poor additive package and not the base oil that was the problem with the Mobil AV. so why this myth keeps being repeated is beyond sensical.
I think it perpetuates because of the similar lackluster additive package in the Aeroshell W15W-50 synthetic blend, which is really only the synthetic or blend marketed for small airplane engines anymore that I know of. Almost every A&P mechanic will try and persuade owners to switch to the SAE 50 Aeroshell W100 if they can’t fly at least 1 hour per week. Unfortunately I think the market is too niche and fraught with regulatory and liability hurdles to warrant R&D for new oils, which is unfortunate.
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