Lambretta Journey

~ a site dedicated to Lambretta C, D, LC & LD's ~

Lambretta Fuel Mixes and Oils

I have added a FAQ at the end of this page for further information.

I hope the information below may be of use to Lambretta LD owners in understanding how complex oils are and why certain oils should be used over others, or if they may be interchangeable.  In the event that I have any issues or problems with my Lambrettas using the fuel mix solution or the oils below, I will update this page.

If you decide to use the information below on your Lambretta, you do so under your own discretion.  Lambretta Journey and sources of information I have obtained below can not be held liable in any way for any issues you may have with your Lambretta.  This is my own research and views and is what I use on my own Lambrettas.

Introduction

During 2018, I have completed a number of reviews into what oils and fuel mixes to use on a Lambretta 1950, 1951, 1952, 1953, 1954, 1955, 1956, 1957 and 1958 LD Mk1 LD Mk2 and LD Mk3 Lambretta.

Oils I use are from two current sources and via eBay and Amazon:

The Lambretta LD 1950’s manual:

Lambretta Journey

A summary of information only on my findings and what I am using are as follows:

Petrol Mix and Fuel: Rock Oil (SAE30 and PP2 Semi Synthetic 2 Stroke Oil)

Classic Rock Oil SAE 30 Data Sheet Download

PP2 Semi Synthetic 2 Stroke Oil Data Sheet Download

  • Some LD’s I am running are mixed with a 4% Rock Oil SAE 30 solution.  This is a recommended solution in the LD 1950’s manual.
  • Some LD’s I am running are mixed with a 3% Rock Oil PP2 Semi Synthetic solution

Other Reported Options:

New engine build – 8% whilst running-in a new engine and then 6%. People have however reported issues with this solution.

Some people use a 5% SAE30 mix solution, rather than the recommended 4%

SAE30 Information

SAE30: The differences with an SAE30 Motor oil and SAE30 Groundsman / 4 stroke / lawn mower solution can be found in the PDF downloadable documents below

Please DO NOT get confused with SAE30 solutions and accidentally buy the cheaper

SAE30 – lawnmower 4 stroke / Groundsman solution for your Lambretta LD.  You should be using the SAE30 Classic Motor Oil solution

PP2 Semi Synthetic.  The PP2 from Rock Oil is a Semi Synthetic 2-Stroke oil. It is claimed to have advanced blending techniques with a low ash formulation which results in super clean burning, minimum carbon deposits and increased power, at the same time exceeding all manufacturers specifications.  It is suitable for use with unleaded, leaded or LRP Petrol as well as Autolube and Pre-Mix 2-Stroke systems.  It is a recommended solution by Lambretta restoration workshops I have made contact with.

Lambretta LD Gearbox Oil,  Rock Oil (SAE30 or SAE40)

Classic Rock Oil SAE 30 & SAE40 Data Sheet Download

The 1950’s manual states to use SAE40.  However, my research has shown that SAE30 works best in temperatures of -5 to +35 degrees, while SAE40 works best in temperatures +10 to +45 degrees.  Based on my use of my Lambrettas (and as I am mixing an SAE30 with unleaded petrol for my fuel), I use an SAE30 oil solution for the Gearbox Oil as well.

Lambretta Journey

Point to note: SAE20; SAE30 or SAE40?  Lower numbers represent thinner oils, and higher numbers are thicker oils.  The advantage of thinner oils on a Lambretta are that they with the clutch plate should not sticking on a cold morning.

Lambretta LD Transmission Oil, Westway Lubricants Ltd (SAE140)

SAE140 Westway Lubricants Ltd Data Sheet Download

I am using the recommended SAE140, mentioned in the 1950’s manual from Westway Lubricants Ltd.  I purchase it from eBay.  I am also still researching ST and EP oils in general at present and their Viscosity information for my own curiosity

Note: A number of people on forums and websites say to use SAE90 for a transmission oil.  This may be due to SAE140 being harder to find nowadays.  For SAE140 or SAE90, my research has shown that there seems to be marginal difference when viewing the first source below, which state a ST90 and ST140 oil with minimal difference.  However, the second source from Castrol implies that if I use an equivalent SAE90 by Castrol (ST90), it is better suited to commercial vehicles. For further information in this area, please read the links and further information below on Viscosity

Useful links below for further information:

Other information:

Data Sheet General Information.  Here I address what the words mean in the data sheet and in the example below, I highlight the differences between the recommended 1950’s LD manual Lambrreta recommended SAE140 Transmission oil solution and the SAE90 solution that may websites and shops may recommend using as an alternative to SAE140

Viscosity Information: – https://en.wikipedia.org/wiki/Viscosity_index

Viscosity (dynamic)

Viscosities

A simulation of liquids with different viscosities. The liquid on the right has higher viscosity than the liquid on the left.

The viscosity of a fluid is the measure of its resistance to gradual deformation by shear stress or tensile stress.  For liquids, it corresponds to the informal concept of “thickness”: for example, honey has a higher viscosity than water.  The higher the viscosity, the thicker the oil.  If we take Westways oil as an example of usage, the information is as follows.  These are examples only of SAE90 (NOT motor oil SAE30) and SAE140 oils for comparison:

Viscosity @ 100°C (cSt) – SAE90 – 19.2
Viscosity @ 100°C (cSt) – SAE140 – 28.09

Viscosity @ 40°C (cSt) – SAE90 – 220
Viscosity @ 40°C (cSt) – SAE140 – 411.14

Viscosity index – https://en.wikipedia.org/wiki/Viscosity

For the Viscosity index, the lower the number, the more the viscosity is affected by changes in temperature.

Viscosity Index – SAE90 – 97
Viscosity Index – SAE140 – 95

Flashpoint – https://en.wikipedia.org/wiki/Flash_point

The flash point of a volatile material is the lowest temperature at which vapours of the material will ignite, when given an ignition source.  It is NOT to be confused with the autoignition temperature, which is the temperature at which the vapor ignites spontaneously without an ignition source

Flash point °C (IP 34) – SAE90 – 215°C
Flash point °C (IP 34) – SAE140 – 235°C

Pour Point – https://en.wikipedia.org/wiki/Pour_point

The pour point of a liquid is the temperature below which the liquid loses its flow characteristics. In crude oil a high pour point is generally associated with a high paraffin content

Pour point °C (IP 15) – -SAE90 –    -12
Pour point °C (IP 15) – -SAE140 –   -9

Specific Gravity – https://en.wikipedia.org/wiki/Specific_gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance.

Specific gravity usually means relative density with respect to water.  If reading the wiki article above, the following should also be used as a reference: https://en.wikipedia.org/wiki/Relative_density

Specific Gravity @ 15°C – SAE90 – 0.893
Specific Gravity @ 15°C – SAE140 – 0.898

Rock (Motor) Oil Information

Typical Physical Characteristics
Viscosity Grade SAE 30 SAE 40 SAE 50
Density @ 15C – 0.885 0.891 0.894
Viscosity @ 40C – 96.1 cSt 144.3 cSt 201.7 cSt
Viscosity @ 100C – 11.3 cSt 14.8 cSt 18.4 cSt
Viscosity Index 103 102 100
Appearance Amber Amber Amber
Product Code 02032 02041 02071

Some FAQ’s

“SAE J300 Standard Some History / Information”

SAE J300 Standard – Wiki Link

The SAE Viscosity Number or “Grade” according to the initial SAE J300 standard was simply an average time in seconds that tested oil would take to flow through the test apparatus.  The SAE J300 standard is an “approximation” and NOT an exact measure.  Some examples of SAE oils and testing are:

  • Any oil that took from 5 to 14 seconds to flow would be SAE 10.
  • Oil that would take 15 to 24 seconds would be labelled as SAE 20.
  • Oil that took 25 to 34 seconds would be SAE 30
  • Oil that took 35 to 44 seconds would be SAE 40
  • Oil that took 45 to 54 seconds would be SAE 50 and so on

Further Information

 

Lambretta Oil and Gas Fuel Ration – 6%, 3%, 4% – Which One?

Resources

In summary, you need to decide for yourself and you will get a different answer from many different people.  Hopefully, this page will help you decide.

Some history: Prior to SAE30 (Introduction date not known) early vehicles utilized a slippery crude oil to help protect the various metal parts.  Before better viscosity oils were introduced, in its older format the crude oil would neither mix well or stick and lubricate components.  It would also not burn completely and therefore had to be used in large quantities (which may have included 6%+) in order for it to work. Interestingly, the Vespa GS160 (1962 to 1964) mentions in it’s manual a mixing ratio required of 5%.

As a result of the crude oil being used in older vehicles, burnt oil (coke – click here) was produced which caused breakdowns and or problems in areas such as the cylinder exhaust port, the piston ring grooves, the combustion chamber in the cylinder head, the piston head / crown and blockage in the exhaust system).

With the introduction on better mixes and blends with the gas, the oil and fuel mix sticks to metal parts better and and burn more completely. As a result, this means less oil mix is required and less de-cokes.

Crankshaft Bearings

  • If you are running a plain-bush little end, some say you can use a use 4% fully synthetic oil.
  • If you have a needle-bearing little end, some say you can use a use 3% fully synthetic oil.

What happens if I add too much oil?

By adding more oil, although you gain more lubrication, you will also be running leaner and run a much greater risk of problems.

Mixing too much oil with gas (Not to be confused with carb problems, such as the float sticking, top ior bottom end or seal break down) may cause your Lambretta to produce smoke.

For further information, here is a useful video link:

  • You Tube Video Link Lean Fuel Mix.

    Does it matter if I leave the fuel in my tank for extended period of time

    Fuel does go off and you should therefore consider using your fuel by 30 to 90 days.  Any further time than this, you should consider replacing it.

    If your intending not to use your Lambretta over certain months, you should consider draining your fuel out of it.

    Search online for “does-gasoline-go-bad”

    In summary as a result of oxidation and evaporation gas can go off in as little as three to six months.  Ethanol-gasoline blends have a shorter shelf life of two to three months.  External resource link – good article Does Gas Go Off – External Link

 

Ethanol & my Lambretta

UK E10 Ethanol

In a small engine fuel tank in a constantly high-temperature, high-humidity environment, it takes three months or longer for E10 and other ethanol blends to take up enough water for phase separation.

Ethanol & My Lambretta

The prolonged use of E10 fuel in an old Lambretta can cause corrosion of some rubbers, alloys used in the engine and fuel systems.

External Government Link

    • Premium 95 – This is the standard petrol grade available at all filling stations. This is currently E5 (95 E5) and is proposed to become E10 (95 E10), which is suitable for almost all petrol-powered vehicles and equipment.
    • Super 97+ – This is the higher-octane petrol grade available at many filling stations. This is proposed to remain E5. It’s suitable for all petrol-powered vehicles and equipment.

 

I have rebuilt my Lambretta Engine. Should I use a greater fuel mix?

Most people add an additional 1% of oil mixtures for an initial 500 to 600 miles.

An advantage of adding more oil is that you lubricate the new parts you have installed better.  However, adding more oil makes your gas weaker and as such, a weaker gas mixture will make your engine run hotter, which you may also want to avoid.

You’ll may need to rejet your carb to allow for the change in fuel oil ratio whilst running in to keep the mixture slightly rich rather than weak and rejet again when run in and using a 3% or less premix.

See here (Not an LD carb, but principles are the same) for information on how to rejet – Scooter Center Carb Rejet External Link 

Why Rejet? To avoid engine seizure its extremely important to make sure that your idle speed is not too low and the mixture is not too weak .

When you deaccelerate from your high speed and shut off the throttle, the engine is still being driven at a high rpm.  However, you now only have a small amount of petrol and oil flowing through the idle jet to lubricate and cool the piston and rings . As a result, you risk seizing engine.

Crankshaft Bearings

  • If you are running a plain-bush little end, some say you can use a use 4% fully synthetic oil.
  • If you have a needle-bearing little end, some say you can use a use 3% fully synthetic oil.

 

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