Oil weight influenced by epa mileage targets?

[EOD Guy]

IMO the thinner viscosity is purely due to the tighter machine tolerances in the engine. My Acura used 0w20, my 2020 Taco uses 0w20 and it seems to work great in my older 07 Taco.

 

[TakaraLC]

For starters a 0W-30 oil or a 0W-40 oil is always going to flow like a 0W oil at any given temperature.

Good thing you said this because I saved time by not bothering to reading the rest. I guess kinematic viscosity at 100C that all manufacturers report is not a thing.

 

[Sugarloafer80]

Using 0W-30 or even 0W-40 instead of 0W-20 in naturally aspirated engines is not an issue.

0W vs. 5W or 10W does not affect longevity. "W" only affects low temperature viscosity that is important during the first few minutes after starting the engine. The lower the "W" number the better because it will allow oil to reach all engine parts faster. Once the engine reaches it's normal operating temperature it's completely irrelevant because hot oil is always less viscous than cold oil. So 0W-20 or 5W-20 oil will have exactly the same viscosity when hot, but 5W will be thicker (and slower to reach bearings, cams, etc.) when cold. If you want your engine to last, use 0W oil, no matter what the number after the dash is.

Now let's talk about -20 vs. -30 or -40. Oil viscosity is important for two reasons: bearing clearance and bearing tangential speed. Bearing with larger clearance and/or lower tangential speed need thicker oil. Bearing with tight clearances and high tangential speed need thin oil, otherwise they will overheat and the oil will get burned. In the 1960s or 1970s bearing clearances were HUGE due to manufacturing limitations, and with thin oil they would just run dry and destroy themselves. Also, large displacement engine normally run at lower rpm, so bearing tangential speeds tend to be lower, requiring thicker oil. Fast forward to 21st century. Tolerances are tighter and bearing clearances are smaller, hence allowing engines to use thinner oil for less friction. Generally speaking, they will also work with thicker (-30 and -40 oils), but they will have more friction losses and the bearings will run hotter.

But then come turbochargers. These turn at extremely high rpms, some of them reaching 200,000 rpm or more. At so high rpms, you MUST use very thin oil, otherwise the bearings will overheat and the oil will turn into charcoal. This will dramatically reduce the lifespan of the turbocharger, if not destroying it right out after a few hours.

For perspective, 0W-20 oil has a kinematic viscosity of of ~9 mm2/s. Aviation oil for lubrication of small gas turbines, which operate at similar rpms as turbochargers, has a kinematic viscosity of ~5 mm2/s. So even 0W-20 oil is relatively thick for a high speed turbocharger. 0W-40 oil has a kinematic viscosity of ~14 mm2/s. You know what will happen if you put such oil in a turbocharger? It will burn, seizing the turbocharger after a very short time.

Bottom line, if you have a naturally aspirated engine you can most likely use 0W-30 or 0W-40 instead of 0W-20 without ill effects. But if you have a turbocharged engine, stick to low viscosity oil unless you are OK with paying for turbo replacement.

I appreciate you give us the BEST explanation of viscosity I have ever read!!! I always thought high powered turbo motors get so much hotter that the oils thin out more.....My statement about running the 30 weight oil was with that lack of knowledge in mind. I fully under the W viscosity. Ow is only a problem on some old motors from my understanding. But......with the issue Toyota/Lexus is having with the new 3.4? turbo? and bottom end wear, which is more important to protect, the bottom end or the turbo?

 

[Sugarloafer80]

Good thing you said this because I saved time by not bothering to reading the rest. I guess kinematic viscosity at 100C that all manufacturers report is not a thing.

THis is a statistic that , until now, has gone over my head. You are making me think. Granted I will still run 15W-50 in my 4C because I am pushing it to its limits and as a result, burning a bit more than I think correct. First time with the thicker oil. Ironically motor has never been as smooth as it was 1this morning after yesterday's oil change. Diffeent vehicle but.......hard working 4 cylinder powerplants.
The one thing i do know, old T4 is not a synthetic and is a bit of a , pun intended, dinosaur...At least run T6

 

[katekebo]

Shaft speeds for turbos being too high for a “thicker” oil is just asinine. Sorry but it is. Want proof? Look at all the turbo diesels, and high performance gasoline engines running around that use much heavier oils that are actually thicker, like 15W-40 etc. To make a given level of boost those impeller/turbine shafts are spinning just as fast as any other turbo in a more pedestrian application. Many of these turbos are not some custom bespoke units specially made for the application and a special unicorn grade of oil.

Borg-Warner, KKK, IHI, Garret, Honeywell, and other turbo manufacturers offer a bunch of different sizes, flanges, and models to choose from. Strangely they all work just fine with a variety of different oil viscosities.

Large displacement diesel engine turbochargers operate around 100,000 rpm. Small displacement gasoline engine turbos turn around 200-300,000 rpm. As you mentioned, they are designed to operate with different oil viscosities. You can use -30, -40 or even -50 viscosity engine with a turbocharger - if the turbocharger is designed to be used with such viscosity oil.
LC turbocharger was designed to be used with low viscosity oil. Using oil with higher than specified viscosity will do more harm than good.

 

[Nardulli]

This is not correct. As Ketekabo explained above, if you run thick oil in a low clearance turbo engine, it will be inadequate.

Part of this is due to thick oil not flowing as well and therefore not getting into bearings etc in a low clearance engine.

Another issue is that thick oil doesn’t flow as good, so oil flow in galleries slow down, which can cause localized hot spots. This is an issue particularly for the turbo because it operates at very high temps. Fast flow of oil in and out turbo ensures proper cooling while also prevents the oil from getting burned. Basically large quantities of oil needs to flow through the turbo to ensure oil inside is recycled before it overheats and burns. Thick oil will not flow as fast and burn before it can be cycled out, and this will eventually cause a clog.

There will also be concerns with components that use oil as hydronic fluid, like lifters used for VVT system and even the oil pump.

Using 0W-30 or even 0W-40 instead of 0W-20 in naturally aspirated engines is not an issue.

0W vs. 5W or 10W does not affect longevity. "W" only affects low temperature viscosity that is important during the first few minutes after starting the engine. The lower the "W" number the better because it will allow oil to reach all engine parts faster. Once the engine reaches it's normal operating temperature it's completely irrelevant because hot oil is always less viscous than cold oil. So 0W-20 or 5W-20 oil will have exactly the same viscosity when hot, but 5W will be thicker (and slower to reach bearings, cams, etc.) when cold. If you want your engine to last, use 0W oil, no matter what the number after the dash is.

Now let's talk about -20 vs. -30 or -40. Oil viscosity is important for two reasons: bearing clearance and bearing tangential speed. Bearing with larger clearance and/or lower tangential speed need thicker oil. Bearing with tight clearances and high tangential speed need thin oil, otherwise they will overheat and the oil will get burned. In the 1960s or 1970s bearing clearances were HUGE due to manufacturing limitations, and with thin oil they would just run dry and destroy themselves. Also, large displacement engine normally run at lower rpm, so bearing tangential speeds tend to be lower, requiring thicker oil. Fast forward to 21st century. Tolerances are tighter and bearing clearances are smaller, hence allowing engines to use thinner oil for less friction. Generally speaking, they will also work with thicker (-30 and -40 oils), but they will have more friction losses and the bearings will run hotter.

But then come turbochargers. These turn at extremely high rpms, some of them reaching 200,000 rpm or more. At so high rpms, you MUST use very thin oil, otherwise the bearings will overheat and the oil will turn into charcoal. This will dramatically reduce the lifespan of the turbocharger, if not destroying it right out after a few hours.

For perspective, 0W-20 oil has a kinematic viscosity of of ~9 mm2/s. Aviation oil for lubrication of small gas turbines, which operate at similar rpms as turbochargers, has a kinematic viscosity of ~5 mm2/s. So even 0W-20 oil is relatively thick for a high speed turbocharger. 0W-40 oil has a kinematic viscosity of ~14 mm2/s. You know what will happen if you put such oil in a turbocharger? It will burn, seizing the turbocharger after a very short time.

Bottom line, if you have a naturally aspirated engine you can most likely use 0W-30 or 0W-40 instead of 0W-20 without ill effects. But if you have a turbocharged engine, stick to low viscosity oil unless you are OK with paying for turbo replacement.

I've been building engines since the 70's. (Sadly, that really dates me) and I have not seen any difference in bearing tolerances. if anything, I've seen modern engines being built looser. (esp Hemi engines) The rule of thumb back then and still today is .00075 to .0010 of clearance per inch of shaft diameter. So if it is a 2" journal, we look for 1 1/2 to 2 thou clearance. If it is a high performance engine, we INCREASE clearance by .0005, so 2 1/2 thou. The 383 stroker I just built for my square body project was set up at 2 3/4 thou as I'm running 20 - 50W high zinc in that one. We're really interested to see what oil analysis tells us over time .

I agree that thinner oils present less resistance to flow. OE clearance specifications are necessarily tight due to the use of energy conserving lightweight oils, relatively high operating temperatures, and a concern for control of noise and vibration, especially in aluminum blocks. Note that the use of "energy conserving" oils is driving this, not necessarily what's best from an engine builder perspective.

And yes, turbos turn fast - really fast. But not at start up and not at idle. Our company operates a twin engine, turbocharged piston airplane. Those engines run at maximum RPM on takeoff and ~70% power during cruise. Oil specified is 20-50W. (!!!) The only way we will grenade a turbo is via shock cooling. As we descend, the turbo inlet temp cannot fall below a specified temp. Those turbos will glow red during extended climbs - with 20-50W oil - and they live just fine.

There's a lot to debate here. Maybe a Land Cruiser forum is not the best place for the discussion. I'm a newbie here so please forgive any breach of decorum.

 

[katekebo]

I appreciate you give us the BEST explanation of viscosity I have ever read!!! I always thought high powered turbo motors get so much hotter that the oils thin out more.....My statement about running the 30 weight oil was with that lack of knowledge in mind. I fully under the W viscosity. Ow is only a problem on some old motors from my understanding. But......with the issue Toyota/Lexus is having with the new 3.4? turbo? and bottom end wear, which is more important to protect, the bottom end or the turbo?

In my opinion, the failure of V35A main bearings has nothing to do with oil viscosity. Toyota claims that the failure was caused by insufficient cleaning, leaving debris from machining. I'm not saying that this isn't the case, but I think there is more to the story that what Toyota is telling us.
If the damage was indeed caused by debris, than no oil viscosity would make a difference. The bearing would get damaged and seize anyway.
However, I think that there is an inherent design problem with the bearing design. For one thing, Toyota made some design modifications as the parts numbers have changed from the original one. Also, engines produced after the cleaning problem has supposedly been solved keep failing. The V35A engine problem is very different from the GM V8 problem for which GM recommended switching to higher viscosity oil. The GM problem is caused by bad journal surface finish (roughness).
Finally, the 0W part of the viscosity number is nothing to worry about. It only matters when the engine is cold, and mainly affects startability in cold weather. Once the engine reaches its operating temperature, a -30, -40 or -50 oil will still be "thinner" than cold 0W oil. Viscosity only goes down with temperature. But low cold viscosity does help the oil to reach all part of the engine quickly.

 

[TakaraLC]

THis is a statistic that , until now, has gone over my head. You are making me think. Granted I will still run 15W-50 in my 4C because I am pushing it to its limits and as a result, burning a bit more than I think correct. First time with the thicker oil. Ironically motor has never been as smooth as it was 1this morning after yesterday's oil change. Diffeent vehicle but.......hard working 4 cylinder powerplants.
The one thing i do know, old T4 is not a synthetic and is a bit of a , pun intended, dinosaur...At least run T6

Yeah a track car is a different beast. Engine oil in that case is maintained at a much higher temperature, which thins it down as oil get less viscous at higher temp. So 15W-50 oil at racing temps may be as thin as 15W-20 during city driving. And of course if you use 15W-20 for racing, it my get too thin. This is also the reason why people warm their engines before track (or do practice laps), as if you hammer a cold engine, it can cause the turbo to oil starve.

Here are some pictures that show very narrow galleries that turbo's use to deliver oil to shaft bearing. Those small openings on the bearing itself are oiling ports which the oil flows to into to lubricate the shaft-bearing contact point.

And this is what happens if the oil doesn't flow though due to burnt oil clogged oil port.

Why Turbos Fail

Why Turbos Fail - Causes and remedies for common turbocharger failures

gcg.com.au

 

[Sugarloafer80]

All very enlightening.

 

[griso]

Using 0W-30 or even 0W-40 instead of 0W-20 in naturally aspirated engines is not an issue.

0W vs. 5W or 10W does not affect longevity. "W" only affects low temperature viscosity that is important during the first few minutes after starting the engine. The lower the "W" number the better because it will allow oil to reach all engine parts faster. Once the engine reaches it's normal operating temperature it's completely irrelevant because hot oil is always less viscous than cold oil. So 0W-20 or 5W-20 oil will have exactly the same viscosity when hot, but 5W will be thicker (and slower to reach bearings, cams, etc.) when cold. If you want your engine to last, use 0W oil, no matter what the number after the dash is.

Now let's talk about -20 vs. -30 or -40. Oil viscosity is important for two reasons: bearing clearance and bearing tangential speed. Bearing with larger clearance and/or lower tangential speed need thicker oil. Bearing with tight clearances and high tangential speed need thin oil, otherwise they will overheat and the oil will get burned. In the 1960s or 1970s bearing clearances were HUGE due to manufacturing limitations, and with thin oil they would just run dry and destroy themselves. Also, large displacement engine normally run at lower rpm, so bearing tangential speeds tend to be lower, requiring thicker oil. Fast forward to 21st century. Tolerances are tighter and bearing clearances are smaller, hence allowing engines to use thinner oil for less friction. Generally speaking, they will also work with thicker (-30 and -40 oils), but they will have more friction losses and the bearings will run hotter.

But then come turbochargers. These turn at extremely high rpms, some of them reaching 200,000 rpm or more. At so high rpms, you MUST use very thin oil, otherwise the bearings will overheat and the oil will turn into charcoal. This will dramatically reduce the lifespan of the turbocharger, if not destroying it right out after a few hours.

For perspective, 0W-20 oil has a kinematic viscosity of of ~9 mm2/s. Aviation oil for lubrication of small gas turbines, which operate at similar rpms as turbochargers, has a kinematic viscosity of ~5 mm2/s. So even 0W-20 oil is relatively thick for a high speed turbocharger. 0W-40 oil has a kinematic viscosity of ~14 mm2/s. You know what will happen if you put such oil in a turbocharger? It will burn, seizing the turbocharger after a very short time.

Bottom line, if you have a naturally aspirated engine you can most likely use 0W-30 or 0W-40 instead of 0W-20 without ill effects. But if you have a turbocharged engine, stick to low viscosity oil unless you are OK with paying for turbo replacement.

I’m with you. Wife’s Subaru uses same oil and the turbo aspect makes the case for thinner oils. The rest is just contrarian barstool talk.

 

[basicxj]

All the more reason to avoid the suggested 10K oil change interval in my books. A constant supply of clean oil with as much of the additive pack still intact should bode well for optimizing everything that depends on its properties.

Toyota is concerned with balancing EPA regulations and sales, powertrain components lasting up to/beyond the warranty period rather than overall engine/turbo longevity at extended mileage.

Oil and filters are about the cheapest things you can put into an engine, so my plan is to at least halve that suggested OCI to stack the deck for long term success. Is it wasteful? Possibly in the eyes of some, but I recycle my used oil and if using shorter OCIs keeps the engine and turbo in better form well beyond the warranty period and avoids costly repairs or replacements, it is a small price to pay in the grand scheme of things. Getting rid of carbon and metallic particles before they have a chance to accumulate in internal passages is cheap insurance.

 

[katekebo]

All the more reason to avoid the suggested 10K oil change interval in my books. A constant supply of clean oil with as much of the additive pack still intact should bode well for optimizing everything that depends on its properties.

Toyota is concerned with balancing EPA regulations and sales, powertrain components lasting up to/beyond the warranty period rather than overall engine/turbo longevity at extended mileage.

Oil and filters are about the cheapest things you can put into an engine, so my plan is to at least halve that suggested OCI to stack the deck for long term success. Is it wasteful? Possibly in the eyes of some, but I recycle my used oil and if using shorter OCIs keeps the engine and turbo in better form well beyond the warranty period and avoids costly repairs or replacements, it is a small price to pay in the grand scheme of things. Getting rid of carbon and metallic particles before they have a chance to accumulate in internal passages is cheap insurance.

100% correct.
The main reason manufacturers recommend 10k miles oil changes is to claim low maintenance costs.
10k miles could be OK under ideal conditions: mostly highway driving on flat roads, under moderate loads and speeds. In real life driving, 5k miles will make the engine last longer. Manufacturers don't care how long an engine will last as long as it makes it past the warranty mileage (60k miles).

 

[Yousef]

You can safely run up to 10W30 as per the user manual here for the same T24A-FTS engine.
The manual also mentions that using higher viscosity might be more suited for higher load/conditions.

 

[basicxj]

100% correct.
The main reason manufacturers recommend 10k miles oil changes is to claim low maintenance costs.
10k miles could be OK under ideal conditions: mostly highway driving on flat roads, under moderate loads and speeds. In real life driving, 5k miles will make the engine last longer. Manufacturers don't care how long an engine will last as long as it makes it past the warranty mileage (60k miles).

I have quietly been stockpiling Toyota 0W20 synthetic and filters/crush washers.

I did 5000 mile synthetic oil changes on my previous ride, and sadly had the misfortune of seeing the top end torn down after a careless tech dropped a bolt into the combustion chamber without noticing, fired it and revved it. Cams were pristine after 120,000 km. Sadly there were a series of cascading failures unrelated to maintenance after that (which is the primary reason I went Toyota shopping). I gave away quite a bit of Pennzoil Platinum Ultra in 5W20 after waving goodbye to that vehicle. I used to maintain enough oil/filters for three changes on-hand, will do the same for this one. Apart from a few opinions, I haven't seen any compelling reasons to disregard Toyota's specified viscosity for this climate.

 

[SlickLC]

I have quietly been stockpiling Toyota 0W20 synthetic and filters/crush washers.

I did 5000 mile synthetic oil changes on my previous ride, and sadly had the misfortune of seeing the top end torn down after a careless tech dropped a bolt into the combustion chamber without noticing, fired it and revved it. Cams were pristine after 120,000 km. Sadly there were a series of cascading failures unrelated to maintenance after that (which is the primary reason I went Toyota shopping). I gave away quite a bit of Pennzoil Platinum Ultra in 5W20 after waving goodbye to that vehicle. I used to maintain enough oil/filters for three changes on-hand, will do the same for this one. Apart from a few opinions, I haven't seen any compelling reasons to disregard Toyota's specified viscosity for this climate.

i used to stockpile oil too but the newly released api sq standard for oil has been rolling out since the beginning of the year. some brands with api sp can currently meet sq standards but some will need to update their formula to meet the new sq standard. the current oem toyota oil will be fine, i personally prefer using the latest standards for the improved engine protection from lspi.

 

[Sugarloafer80]

You can safely run up to 10W30 as per the user manual here for the same T24A-FTS engine.
The manual also mentions that using higher viscosity might be more suited for higher load/conditions.

View attachment 45016

BINGO!!! Conditions dependent requirements...Brilliant just like the good old days!
I guess the biggest reason I have called some specs into question is because of the problems we are experiencing out there all seems to be on 0W-20 vehicles. Please correct me if i am wrong. It is now understood the GM issue was a manufacturing flaw. Sound like the Toyota issue was also. Maybe we really are back to square one?
I see no reason for folks down south (anywhere it rarely goes below freezing) to use a 0W oil however and especially in the real hot climates, my go to would be 5W-30.
Based on all the prime info given above, I will just stay with the 0W-20 as it will spend winters in Maine and it is a highway driver. Probably will cut service intervals back to 7500 miles however. Too easy to DIY. I promise not to overfill hehe

 

[TakaraLC]

BINGO!!! Conditions dependent requirements...Brilliant just like the good old days!
I guess the biggest reason I have called some specs into question is because of the problems we are experiencing out there all seems to be on 0W-20 vehicles. Please correct me if i am wrong. It is now understood the GM issue was a manufacturing flaw. Sound like the Toyota issue was also. Maybe we really are back to square one?
I see no reason for folks down south (anywhere it rarely goes below freezing) to use a 0W oil however and especially in the real hot climates, my go to would be 5W-30.
Based on all the prime info given above, I will just stay with the 0W-20 as it will spend winters in Maine and it is a highway driver. Probably will cut service intervals back to 7500 miles however. Too easy to DIY. I promise not to overfill hehe

Another thing to consider, even in south, is since the North American variant is hybrid (Middle East variant is not), so the oil will remain cooler overall since engines shuts off frequently.

 

[Sugarloafer80]

Never thought of that. Even cruising on the highway at 75-80 mph??

 

[basicxj]

When I was test driving and trying to buy a Land Cruiser, all the sales people I dealt with kept saying the engine does not go on/off while driving and that the hybrid system was only designed to act as a helper to the gasoline engine in low RPM to provide extra torque.

After driving ours for a while, I can confirm it actually will shut off (RPM on tach goes to zero and needle disappears) while cruising at highway speeds. This usually happens when not actively using the accelerator, like when you are up to desired speed and are coasting along or are coasting on a downhill stretch. It'll also happen in stop & go traffic when starting off or stopping gently. So in this sense it does behave like other hybrids I have driven, just less so. Whether that is enough to drop oil temperatures is a matter that would require some monitoring with a 3rd party app (unless you happen to have a means to display oil temperature on screen).

 

[TakaraLC]

Never thought of that. Even cruising on the highway at 75-80 mph??

I have seen it turn off at highway speeds if there is a downslope. But in those speeds, oils should remain cool from the air flow either way. When I used an OBD scanner in ~90F weather, oil was barely touching 195F at 75mph. You probably need to get close to 100mph or so for the oil temp to go above 220F.