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I had a guy mention to me that once synthetic oil is used in an engine you can never go back to conventional oil. Is there any truth to that statement?
 

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Myth Busted maybe 30 years ago.

I had a guy mention to me that once synthetic oil is used in an engine you can never go back to conventional oil. Is there any truth to that statement?
I've followed YouTube channels through periods where we consumers of content could ask Ericthecarguy questions for the Vavoline engineers.

These were seriously amazing scientists. I learned more than I'll ever remember to tell. Look him and Valvoline up on Google and watch the video.

I will say a few things I recall.

That's a complete and utter myth. Switch whenever you want. The only time this wasn't true was in the 80's. Engines needed to be on one or the other, and mostly the other. Synthetics at the time had an accident where they shrunk up seals and made a bunch of engines leak or something. If you always used one or the other you were good.

It's modern times now. All synthetic oils and conventional oils labeled with the right specifications for your car or motorcycle will do the job. Some better than others of course. Synthetics always have benefit over conventional. They protect better.

My 2017 Yamaha WR250R hates Castrol Synthetic 10w-40 motorcycle approved oil. Made the clutch slip. Took 2 weeks of conventional to go back to normal. I did fine with semi-synthetic one time by Honda. Motorcycles with wet clutches need very special oil which is low on additives so that the wet clutches don't get slippery. Honda and Yamalube are the some of the lowest on additives, so I probably can get away with semi-synthetic either way, but I'm worried at trying synthetic now. Took 2 weeks for the clutch grab to not be at the end of my release on a brand new motorcycle.
 

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Motorcycles with wet clutches need very special oil which is low on additives so that the wet clutches don't get slippery.
Bit of an urban myth that motorcycle 4T oils need less additives so that the wet clutches don't slip.

Actually 4T engine oils need just as much detergent (to keep the engine clean), dispersant (to keep contaminants in suspension), anti-wear additives (to prevent wear on highly loaded surfaces), anti-oxidants (to prevent the oil burning and thickening - synthetics need this less as they have naturally high anti-oxidation properties), viscosity index improvers (to make multi-grades - synthetics have a naturally high VI, viscosity index, so are multi-grades anyway), pour point improvers and other additives as a passenger car motor oil (PCMO) where the oil doesn't lubricate the transmission and wet clutch.

What they don't need is the friction modifier which is usually put in to SAE 0W-, SAE 5W- and SAE 10W- multigrades to help the car engine achieve Federal fuel efficiency targets (CAFE, corporate average fuel efficiency).

CAFE is a fuel consumption figure set by the EPA that auto manufacturers must meet. It is the average of the fuel consumption of all the cars (and there's a separate light truck standard) that the manufacturer makes in a year. If the manufacturer doesn't meet the CAFE limit I think they are fined $50 for every car they manufactured for every 1/10th of a mpg they missed the target by.

If the CAFE limit was 36 mpg and Ford made 1,000,000 cars, 50,000 of which were 5.0L Mustangs with a fuel consumption of 15 mpg, then they would have to sell a lot of Focuses with a fuel consumption of 40 mpg to meet the CAFE limit. If their average CAFE turns out to be 35.7 mpg then they'll be fined $150,000,000. The move to friction modified PCMOs and low viscosity engine oils (eg. SAE 0W-20) is driven by CAFE, friction modified and low viscosity oils create less internal friction and might contribute a 1/10th of a mpg drop in fuel consumption.

However, the friction modified additive used in low viscosity PCMOs will contribute to clutch slip in a motorbike transmission, so motorbike 4T oils are tested against a Japanese standard (JASO MA or MA2) to determine that they do not cause wet clutch slippage.

So motorcycle engine oils do need high levels of additives, the same sort of level of functional additives as a PCMO, but they do not want the friction modifier that PCMOs tend to have.

Have a bike with a wet clutch, then use a motorbike engine oil which displays the JASO MA or MA2 classifcation. A lot of PCMOs and diesel engine oils of 10W-40, 15W-40 and above do not have that friction modifier in them so are suitable for use in a wet clutch motorbike engine/transmission, many here do use diesel engine oils in their bikes. If in doubt, check for that JASO MA or MA2 classification on the bottle.
 

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Thanks Steve, more good information about oil.

Wasn't there a time when esters in the early synthetic oils (about 40 years ago) did something to seals that could cause problems?
If so I'm guessing that's where the "you can never go back" myth comes from. Or maybe it was a myth even back then...
 

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When reading Kiwi Steve's posts is it just me, or does anyone else have to get a cup of coffee, clear their minds, shut off all outside noise and distractions, and really CONCENTRATE to even hope to gain some of the useful information he posts?
 

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When reading Kiwi Steve's posts is it just me, or does anyone else have to get a cup of coffee, clear their minds, shut off all outside noise and distractions, and really CONCENTRATE to even hope to gain some of the useful information he posts?
I understood JASO MA1 and MA2. :) LOL

It was a couple years ago when I put massive studying into motorcycle oils so I could understand why motorcycle oils were different. Apparently I got it wrong, or forgot in the last 2 years what was really up.

I loved the detailed, and most likely more correct post than mine.

So this is what confuses me now.

Yamalube and Honda's motorcycle oil is VERY low in all additives just about. So if there's just one thing they aren't supposed to have, why are these expensive oils cheaping out on everything else?

I really need to rethink what I was thinking when I put tens of hours into research before making this simple video:

Please tell me what I understood wrong.
 

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@Kiwi Steve

Could you tell me what it means to have a naturally high VI?

I understood the newer lighter oils being there just to help with a 1/10 or 2 of a percent of gas mileage. That's what I learned when Mobil 1 announced their 0w-30 oil line up years ago. I did the math and the savings in gas would definitely not pay for that more expensive oil, but if I was facing fees like say Ford will now that they won't make anything but the Mustang car, SUV's and Trucks, I'd shove some 0w-20 in an engine without redesigning the engine too.

Yeah, that's right, I caught you Ford. My mother's 99 Mercury Sable? 5w-30. The 2005 Ford Taurus? 5w-20. SAME ENGINE.

Though research supports that we were already okay to use thinner oils, we just didn't know better, to their credit, lol.
 

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Now my Yamaha rips it's 10w-40 down to 5w-20 in just a 1000 miles, so I definitely can't try thinner oil there! I think single cylinder engines must be really hard on oil, or the lack of additives just makes the viscosity get lost quickly. What do you all think?

Note: this was done with multiple oil changes with Blackstone Labs.
 

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I used to hear this myth and it got explained to me years ago in basic terms.

Basically dino oils have very inconsistent molecular size so to speak, and synthetics are very consistent and and tighter. So basically if you are using dino oil you can leak more and if you switch to synthetic and/or then back, the smaller molecules are able to leak through the gaskets easier, but it all boils down to what condition your motor is actually in way more than the oil its self (provided it is proper and of good quality). I switch my Winger to synthetic on all levels from the grease to to final drive to the engine. It was on Dino oil for the first 42 years of its life.

All that said, a new thing I have heard of recently also is something about dino oils by nature will cause the seals to swell ever so slightly, and I personally dont know if that is truly the case on Dino v/s Synthetic oils, but it seems to have some plausable merit that someone knowing more on this subject than I could explain.
 
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I used to hear this myth and it got explained to me years ago in basic terms.

Basically dino oils have very inconsistent molecular size so to speak, and synthetics are very consistent and and tighter. So basically if you are using dino oil you can leak more and if you switch to synthetic and/or then back, the smaller molecules are able to leak through the gaskets easier, but it all boils down to what condition your motor is actually in way more than the oil its self (provided it is proper and of good quality). I switch my Winger to synthetic on all levels from the grease to to final drive to the engine. It was on Dino oil for the first 42 years of its life.

All that said, a new thing I have heard of recently also is something about dino oils by nature will cause the seals to swell ever so slightly, and I personally dont know if that is truly the case on Dino v/s Synthetic oils, but it seems to have some plausable merit that someone knowing more on this subject than I could explain.

Great information. I can help with that. Yes synthetics are more consistent on the chain length of the molecules. They actually need less additives to stay stable in viscosity, while dino oils actually need a lot more modifier and it doesn't last as long.

As far as swelling up gaskets. That's more the function of high mileage oils or Mobil 1's extended performance. I just like the "regular" fully synthetic oil after I learned that like high mileage oils, extended performance swelled up seals, which sounds great if you're leaking, but swollen gaskets get weak and fail. New gaskets conversely just won't last as long.

Avoid oils promising better seals. Short run good. Long term bad.
 

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When reading Kiwi Steve's posts is it just me, or does anyone else have to get a cup of coffee, clear their minds, shut off all outside noise and distractions, and really CONCENTRATE to even hope to gain some of the useful information he posts?
Kiwi always seems to offer more information than is normally required to answer a question. I guess that's just Steve being verbose. That's what he does.
 

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I think the seals reacting to the type of oil is related to fuel system seals reacting to ethanol in gas. This was true, but better material is now used to make them, so they don't react as much. The OEM seals that were in my '70 Honda will be affected by some oils and ethanol, but newer replacements don't seem to be. Everything changes, especially the seals, which have to do their job longer, and with less friction, than they did before the CAFE rules.
 

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When reading Kiwi Steve's posts is it just me, or does anyone else have to get a cup of coffee, clear their minds, shut off all outside noise and distractions, and really CONCENTRATE to even hope to gain some of the useful information he posts?

Definitely require a second reading, but as an expert in the field he wants to ensure we get the right information.
 
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It was a couple years ago when I put massive studying into motorcycle oils so I could understand why motorcycle oils were different.
Here's the important part as I see it: Use an oil of the type recommended by the people that designed your bike. Change it at the intervals they recommend you change it at.

Go for a ride and don't worry about it.
 

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Could you tell me what it means to have a naturally high VI?
OK, here's Lubriction 102 for those who can stand another twenty page missive :grin:

VI stands for 'viscosity index', its a number which shows the rate at which the oil changes viscosity as temperature changes. Its used to describe not only finished oils but base oils as well.

The lower the number the more the oil changes viscosity with temperature change. That's BAD as if it's thin enough for the engine to turn over at start up temperature then it'll be too thin to keep a lubricant film between rotating surfaces at engine operating temperature.

The higher the number then the less the oil changes viscosity with temperature change, the less it thickens as temperature drops and the less it thins as temperature rises. That's good, an oil which allows rotation at start up temperatures won't have thinned out as much by the time it reaches engine operating temperatures and will still provide a fluid film between moving surfaces and reduce friction and prevent wear.

A good quality mineral basestock will have a VI around 95 to 105. You can add Viscosity Index Improvers (VII) to that to make multigrade engine oils, a mineral based multigrade engine oil might have a VI of 115 to 120.

However, synthetics like poly alpha olefins (PAO), the most common synthetic used in manufacturing oils, will have a natural VI in the area of 140. Therefore, using a synthetic with a naturally high VI you don't have to use a viscosity index improver to make a multigrade, you can get a wider multigrade (eg an SAE 5W-40 synthetic instead of a mineral SAE 15W-40), there's no viscosity index improver to shear down in service (you start with an SAE 15W-40 and end up with SAE 5W-20 - not good for an engine designed for an SAE 15W-40), and you can produce low viscosity multigrades (eg SAE 0W-20, 5W-30) which don't evaporate away in service.

Regarding engines using SAE 0W-20 or other low viscosity multigrades, there will be changes to the internal design of the engines. They'll probably have low tension rings to reduce internal friction to help meet that CAFE requirement. The oil distribution system will also be designed for greater volume flow. Lubrication depends on quantity of oil, pressure is incidental - the volume of oil moving into the wedge between two moving surfaces creates pressure to keep moving surfaces apart, it's called hydrodynamic lubrication.

Consider an engine with a tap on the oil inlet into the engine oil galleries after the pressure sensor. and no relief valve. With clean unblocked oil galleries the oil will flow and the pressure gauge will give a reading based on internal fluid friction of the oil flow. Now, close the tap, the oil flow stops, the pressure gauge reading will go through the roof. Which situation is best? Lower pressure and full flow or higher pressure and no flow? In the case of high pressure/no flow the engine will fail. Mind, too low pressure can mean oil leaking out of the lubrication system and that can cause engine failure too. Vehicle manufacturers install oil pressure gauges only because they're cheaper than oil flow gauges.

Now, the SAE W grade. Its measured completely differently to the SAE high temperature grade, its measured at temperatures between -10 deg C (SAE 25W) and -40 deg C (SAE 0W). High temperature grade is measured at 100 deg C and at 150 deg C under high sliding forces to duplicate operating conditions in the engine. Though the number of an SAE W grade is lower than the number of the high temperature grade, the W oil is not thinner, it is considerably thicker, its just measured and described differently.

Look at an SAE 10W-30. The SAE 10W grade will be 7000 centiPoise (cP) at - 25 deg C and be less than 60,000 cP at -30 deg C. At 100 deg C, the SAE 30 oil will have a viscosity between 9.3 and 12.5 centiStokes (cSt) - see they even use different viscosity units for low temperature and high temperature viscosity grades. Oil technologists usually calculate the oil's VI from its 40 deg C and 100 deg C viscosities.

Time for a break, have a cuppa and those that want to can read the post again.
 

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Yamalube and Honda's motorcycle oil is VERY low in all additives just about. So if there's just one thing they aren't supposed to have, why are these expensive oils cheaping out on everything else?
There can be a bit of confusion between the lack of additives and that an engine oil is 'low ash'.

API engine oil classifications for the last 3 or 4 classifications have concentrated on reducing damage to the exhaust emissions control equipment. Emissions control equipment is poisoned by lead (so unleaded gasoline), sulfur and phosphorus. The last two are common components in an engine oil, coming from the common anti-wear compound zinc dialkyl dithiophosphate (ZDDP). This compound, along with metallo-organic detergents (to keep the engine clean) contribute to an engine oil's 'sulfated ash' - this is a measure of the metallic based compounds in the oil formulation (usually calcium sulfonate detergents and ZDDP anti-wear additive).

So modern engine oils are moving to 'low ash', there are limits on the amount of 'sulfated ash' that an engine oil can have in it, as well as limits on the level of sulfur and phosphorus.

But, "low ash" doesn't mean less additives. You still need detergents and anti-wear additives to keep the engine clean and prevent wear. Its just that modern engine oils uses different (and more expensive) chemistries to provide detergency and anti-wear which don't contribute to the 'sufated ash' level of the oil.

Yamalube and Honda Genuine oil will NOT be low additive oils, however they will be LOW ASH oils - they will contain additives which just don't show up on the usual indicator of additive content - sulfated ash. Modern engine oils are also sometimes referred to as 'low zinc' oils, indicating that the common anti-wear agent ZDDP is used in reduced amounts. People take the zinc level of an engine oil as an indication of the oil's anti-wear performance. But other organic/non-zinc chemistries will be used to provide anti-wear performance. A low-zinc oil still has excellent anti-wear performance even though its zinc level is reduced. Low zinc oils may have zinc at a level of 700 to 800 parts per million (ppm) wherreas old 'full' zinc oils would have had zinc levels of 1200 to 1500 ppm. But remember, zinc is only an indication of the level of sulfur and phosphorus atoms in the ZDDP molecule. Zinc doesn't provide anti-wear performance, its just an indicator of the level of sulfur and phosphorus which do the actual anti-wear work.

Its the additives that do all the work in an engine oil (apart from maintaining an oil film between moving surfaces which is dependant on the oil viscosity. Additives keep engine surfaces clean, disperse and suspend deposits until oil drain, stop oil oxidation and thickening, neutralise acidic byproducts of combustion, reduce wear, prevent foaming, reduce wax formation at low temperatures, prevent rust and corrosion. An engine oil without additives would probably last only a couple of hundred miles or so before it oxidised and thickened and sludged up the engine. It wouldn't prevent wear on highly loaded components like cam lobes, in the ring belt area and in bearings. The oil would be too thick to start the engine in winter, and when up to operating temperature would be too thin to prevent wear on any moving surface. It's the additives which do the work in an engine oil.
 
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