Modern 2-stroke oils in vintage motors

[chzuck]

There is an ongoing debate about using modern 2 stroke oils in vintage 2 stroke motors. On the one side are those who say you must use what the manufacturer recommends, which is usually a mineral oil such as AeroShell 100 Aviation oil or SAE 40 or 50 non-detergent oil. These individuals claim the newer oils will ruin or reduce the life of the vintage motors. On the other side are those who say the modern 2 stroke oils will lubricate better and result in less smoke and oil dripping out the muffler. I am on the side of the later and the motor I am referring to is shown in the attached photo. This motor powered the Frazer ROTOTILLER made in 1946 until 1950. It has needle bearings on both ends of the rod and HD ball bearings on the crankshaft which used leather seals, but many have changed over to newer neoprene seals.

I am looking for information to support my side of the argument, besides my own experience. Years ago I rebuilt one of these motors and after break in I used a product call Golden Spectro High Point semi-synthetic, which at the time my brother was using in his racing motocross bike. OEM manufacturer of the motor called for a 16:1 mix and I ran 40:1 for about 8 years with no problems.

Its probably a loosing battle to change anyone's mind on the other side, but I cannot let them bash the newer oils with putting up argument. In the "discussions" that I have been involved in, I never bash their old oils. Their is one individual that constantly infers that if one uses the modern oils, the engine will be ruined. I think he is one of those persons that has the mindset, "it's my way or the highway".

I am sure collectors or users of the vintage chain saws or the Maytag motors hear the same thing. By the way, I have been using Lucas semi-synthetic at shows in my Maytag that powers a fan without issue.

 

[BrianF]

Somewhat on point, I run 50:1 with conventional and semi synthetic oil as premix on my 1974 built sleds. The oils are nothing fancy, for use with lower powered air cooled engines and not with exhaust valves. The manual calls for 50:1 when using "OMC" and 32:1 with other oils and not sure with motor oil. Now, the 437cc air cooled opposed twin does use needle bearings. Has worked great for several hundred miles and 6 years with my use.

 

[Elkins45]

Modern oils benefit from decades of advances in lubrication research and formulation. Why wouldn’t you want to take advantage of that?

 

[Rand]

Do you think an old lawnboy spec'ing 16:1 is adequately lubed at 50:1?

 

[Chris142]

The Lucas oil is iso GD rated. It's good stuff.

I personally would not have a problem running it @32-40:1 as long as you have roller bearings. Some older 2 strokes used plain bearings and I don't know enough about those to comment.

 

[chzuck]

Modern oils benefit from decades of advances in lubrication research and formulation. Why wouldn’t you want to take advantage of that?

My point exactly. I am unable to understand how those people think.

 

[BrianF]

@Chris142 thats where I was headed to with that. Roller vs plain bearings.

 

[Chris142]

plain bearings.

I'm guessing those would need lots of oil regardless of oil type. Didn't they run like 16:1 in those back then? If so even a modern oil mixed at that ratio would burn much cleaner than a sae 40 oil would.

 

[Japanese]

I'm guessing those would need lots of oil regardless of oil type. Didn't they run like 16:1 in those back then? If so even a modern oil mixed at that ratio would burn much cleaner than a sae 40 oil would.

Bushing bearings require at least 25:1. Needle bearings you should be fine with 50:1, I like to run them at 40:1 and 30:1, depending on the displacement and if it's ram air cooled or has a turbine.

 

[Japanese]

There is an ongoing debate about using modern 2 stroke oils in vintage 2 stroke motors. On the one side are those who say you must use what the manufacturer recommends, which is usually a mineral oil such as AeroShell 100 Aviation oil or SAE 40 or 50 non-detergent oil. These individuals claim the newer oils will ruin or reduce the life of the vintage motors. On the other side are those who say the modern 2 stroke oils will lubricate better and result in less smoke and oil dripping out the muffler. I am on the side of the later and the motor I am referring to is shown in the attached photo. This motor powered the Frazer ROTOTILLER made in 1946 until 1950. It has needle bearings on both ends of the rod and HD ball bearings on the crankshaft which used leather seals, but many have changed over to newer neoprene seals.

It depends on a few things. Usually with needle rod bearing, displacement over 125cc, and max. RPM b/w 6,000-8,000 - you should be fine with 40:1 ratio of any modern oil. However, the ROTOTILLER is a farm equipment and run on uneven terrain, sometimes in mud and may till, plow, or tow - all of those put additional stress on the engine and increase its heating.

First, there are myriad of new modern 2-stroke oils varying from SAE 20 to SAE 40 viscosity, depending on the application. Boat and snowmobile oils are usually thin SAE 20 motocross oils are usually thick about SAE 40. The boat and snowmobile oils are lower viscosity because they need to flow well at lower temp + all boats are water cooled and snowmobiles run in cold temp. These oils are ashless for environment purposes which affects their lubrication. Also these oils are not recommended for farm equipment and air cooled engines and if used the amount of oil should be doubled. For example, if your run 50:1 SAE 40 oil, you should go to 25:1 with SAE 20. I'm talking about modern synthetic oils.
On the other hand there are wonderful motocross oils that will suit you well even at 50:1. Some of those are:
Motul 510 (SAE 30) semi synthetic - $20 a quart
Motul 710 (SAE 30) - $20 a quart
Motul 800 (SAE 40) - $30 a quart
Amsoil Saber (SAE 40) - $17 a quart
Honda HP2 (SAE 50) - $15 a pint
All of these are high end full synthetic competition oils, available online with free shipping.
So, if we don't talk about particular modern oil brands, the argument is pointless.

Second, most of todays 2-stroke engines are water cooled and run at lower temps than air cooled engines. Also they are made with better more sophisticated metals and alloys than older engines. So lower working temp + better metals allow them to run less oil or leaner ratios, but no leaner than 50:1.

Third, there is a correlation between engine displacement and its oil ratio. What displacement is the ROTOTILLER?
Small displacement engines always need more oil because have less cooling surface aria and dissipate heat worse than larger displacement engines (especially when relying on ram air than air turbine). Meaning 2-stroke engines up to 125cc require at least 30:1. Engines of 250cc and larger could be fine with 40:1 or 50:1. This is specifically valid for air cooled engines.

Fourth, engines that run to about 8,000 RPM usually require less oil than engines that run at 10,000 and over RPM. Race go-karts run to about 15K-17K and run 16:1 and 12:1 modern thick full synthetic oils. After 10K RPM the oil should be doubled. What is the max. RPM of the ROTOTILLER?

 

[fozzdesy2001]

Do you think an old lawnboy spec'ing 16:1 is adequately lubed at 50:1?

I would mix it at the ratio it was made for, I mean, are you using that vintage machine every day or just to show it off? It lasted to the vintage age on a stout oil-to-gas ratio, so why change it now? Use Lawnboy 2-cycle to really get the vintage vibe

 

[Opelman]

I'm guessing those would need lots of oil regardless of oil type. Didn't they run like 16:1 in those back then? If so even a modern oil mixed at that ratio would burn much cleaner than a sae 40 oil would.

I'm working on a David Bradley saw right now which calls for 11:1 on the tag. 12 oz. non detergent 30 to 1 gallon of gas. The plain bearing engines seem to do better with the super viscous goo mix. My theory is that it helps somewhat with sealing old seals trying to deal with a crankshaft flopping around in a bushing which requires clearance to get lube in rather than a bearing running much tighter. I'm curious as to how much better modern 30ND is compared to days of old too. I wouldn't have a problem running a modern oil in a vintage engine as long as the ratio used provides enough lubrication.

 

[hemitom]

Somewhat on point, I run 50:1 with conventional and semi synthetic oil as premix on my 1974 built sleds. The oils are nothing fancy, for use with lower powered air cooled engines and not with exhaust valves. The manual calls for 50:1 when using "OMC" and 32:1 with other oils and not sure with motor oil. Now, the 437cc air cooled opposed twin does use needle bearings. Has worked great for several hundred miles and 6 years with my use.

On our older sleds when we had them we ran 40:1. never felt comfortable leaning them out at 50:1 .
Always ran good on that mix and never had any bearing issues did smoke a bit at idle though as all sleds did back then.
The most abused sleds that we had were a 1972 elan 250 single and a 1969 olympic 335 can't even imagine how many miles we put on them from November to march /April I don't think the poor engines ever got a chance to cool down LOL.
And also how much our old man complained about the gas bill
We also had
1. 1969 Nordic 640.
2. 1971 Nordic 440.
3. 1973 Olympic 440.

 

[chzuck]

The Lucas oil is iso GD rated. It's good stuff.

I personally would not have a problem running it @32-40:1 as long as you have roller bearings. Some older 2 strokes used plain bearings and I don't know enough about those to comment.

Needle bearings on both ends of the rod. I forgot to mention that this is low rpm for a 2 stroke, develops its horsepower at 2700rpm.

Third, there is a correlation between engine displacement and its oil ratio. What displacement is the ROTOTILLER?
Small displacement engines always need more oil because have less cooling surface aria and dissipate heat worse than larger displacement engines (especially when relying on ram air than air turbine). Meaning 2-stroke engines up to 125cc require at least 30:1. Engines of 250cc and larger could be fine with 40:1 or 50:1. This is specifically valid for air cooled engines.

Fourth, engines that run to about 8,000 RPM usually require less oil than engines that run at 10,000 and over RPM. Race go-karts run to about 15K-17K and run 16:1 and 12:1 modern thick full synthetic oils. After 10K RPM the oil should be doubled. What is the max. RPM of the ROTOTILLER?

23 cubic inches 377cc
5hp @ 2400 rpm
3" bore, 3 1/4" strokee

 

[Japanese]

23 cubic inches 377cc
5hp @ 2400 rpm
3" bore, 3 1/4" stroke

Relatively large displacement and low RPM.
That engine is designed to run at 16:1 (or 1/2 pint per gallon) SAE 40 or 50 oil, regarding the manual on your website (the link and image below). I'm assuming that ratio is because the ROTOTILLER was supposed to be used for farm work in hot summer days. However, if you use it only for riding 40:1 ratio of quality synthetic SAE 30 or 40 oil should be fine.

I would mix it at the ratio it was made for, I mean, are you using that vintage machine every day or just to show it off?

This is usually true - keep the recommended ratio regardless of the oil type.

I would recommend:
Use 40:1 any thick SAE 30 and 40 motocross/road racing full synthetic oil like Motul, Amsoil Saber.
You may also use 16:1 any boat, snowmobile, multi-purpose oils like Lucas, Pennzoil, Valvoline, Castrol at Walmart. However, they are usually SAE 20. I really don't recommend that.
In this case (and any other) the oil viscosity dictates the ratio.

I am looking for information to support my side of the argument, besides my own experience. Years ago I rebuilt one of these motors and after break in I used a product call Golden Spectro High Point semi-synthetic, which at the time my brother was using in his racing motocross bike. OEM manufacturer of the motor called for a 16:1 mix and I ran 40:1 for about 8 years with no problems.

This is the oil your brother had used.
https://spectro-oils.com/en-us/golden-spectro-premix-concentrate--361418
"Use according to motorcycle manufacturers’ recommendations, or at 50:1..."
"For Racing Use:
Golden Spectro Motorcycle Pre-mix can be used according to the manufacturer’s recommended mix ratio. Otherwise, use the ratio recommendation on the back label. (42:1)" - it's interesting because the back label says use at 52:1 (see below).

Per the technical sheet the oil viscosity is 12 (mm2/s) at 100°C which makes it SAE 30 oil on the thicker side.
https://spectro-oils.com/Pdf/TI/Spe...IX-CONCENTRATE_1022442_EN_20241122-172614.pdf

It's sold for about $12 for 12oz on eBay and it says on the back that 12oz are good for 5 gallons which is 52:1 ratio.
https://www.ebay.com/sch/i.html?_nkw=Golden+Spectro+2-Cycle&_sacat=0&_from=R40&_trksid=m570.l1313

http://www.zucksrototillers.com/TechInfo.html

http://www.zucksrototillers.com/opmanual.pdf

 

[Japanese]

Third, there is a correlation between engine displacement and its oil ratio. What displacement is the ROTOTILLER?
Small displacement engines always need more oil because have less cooling surface aria and dissipate heat worse than larger displacement engines (especially when relying on ram air than air turbine). Meaning 2-stroke engines up to 125cc require at least 30:1. Engines of 250cc and larger could be fine with 40:1 or 50:1. This is specifically valid for air cooled engines.

Here is a proof that smaller displacement engines needs more oil.

Motul Kart Grand Prix 2T
https://azupim01.motul.com/media/motulData/DO/base/KART_GRAND_PRIX_2T_en_FR_motul_20210414.pdf
This oil is 17 cSt at 100°C which makes it SAE 50 oil. Still oil ratios are generous because it's designed to run in engines reaching up to 23,000 RPM.

Take a look at the section Recommendations:

Mixing ratio:
- 100 cc: 6%
- 125 cc: 4%

For the smaller displacement engines is recommended more oil.

 

[chzuck]

When I was running the tiller at 40:1 the only thing I noted was that on second pass tilling deep it would shutoff at times. I think the gas boiled and created vapor lock. The cooling discharge exits right at the fuel bowl/strainer that was used much like many motors used back then. There was never any indication that the motor was getting hot to the point of seizing.

I realize there are some people that it is impossible to convince them of anything other than what they believe. This fellow claims he ran "tests" that proved the engine ran hotter with 2-stroke oil. I ask for him to elaborate and he as much as said I was not telling him what to do. How do I know what oil he tried? Did he even use a temperature device? All I can do is when he makes his claim, to be there offering alternatives and tell owners to do their own research and make their own decision.

Japanese, thank you for the information and links.

 

[Japanese]

I ask for him to elaborate and he as much as said I was not telling him what to do. How do I know what oil he tried? Did he even use a temperature device?

You are welcome.
Get some cheap $10-20 infrared thermometer on eBay or Amazon and check the temp with different oils for yourself. You can take a picture for those guys that like to argue.
https://www.ebay.com/itm/2058182169...bOUYhvV/2McgdJg7E8nwRF3A==|tkp:Bk9SR9bj-9n5Zg

 

[Japanese]

Take a look at the section Recommendations:

Mixing ratio:
- 100 cc: 6%
- 125 cc: 4%

For the smaller displacement engines is recommended more oil.

One thing that needs to be mentioned about the Motul kart racing oil is that 100cc requires 6% (12:1) oil because those carts are air cooled and the 125cc karts are most of the time are water cooled, so 4% (25:1) is sufficient for them.

^This is for the people who say that the oil ratio is the same for both air or water cooled engines.