Oils and Lubrication



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The two-stroke engine is lubricated by means of an oil-mixture added to the fuel, usually measured manually and added to the fuel tank or (on some later models) by means of an automated oil mixer or "oil injector" device which pulls oil from a separate reservoir and introduces it to the fuel in the carburetor's venturi section. The recommended oil type and oil ratio varies by engine model configuration and of course by the method of mixing, be it manual or automatic. Manual mixing can be made easier with the use of an appropriate measuring cup designed to accommodate the proper ratio for your model of scooter.

Remember, it is a very bad idea to run the wrong oil mixture ratio and it should be stressed that too much oil can cause just as much damage as too little oil. Far too many riders make the mistake of adding "just a little extra for good luck," not realizing that too much oil will drastically lower the overall fuel octane rating causing potential overheating from pre-detonation. Too much oil also causes power loss, spark plug fouling, excessive carbon build-up and a myriad of other issues.

On the flip-side of that coin, some people will contend that with the advanced protective qualities of modern oils, one can get away with using lower percentage mixtures on early, high-ratio engines. While there is something to be said for that logic, our personal and professional philosophy on this is to use a low viscosity oil on these machines, but always at the factory recommended ratio. There are factors inherent in the design of these engines that dictate the ratios. These factors are based more on the volume of oil and its flow-properties to ensure that it gets to where it needs to be efficiently than on the actual protective properties of the oil itself. Keep in mind that this information applies to early, high-ratio, low performance stock machines and is in no way an endorsement of the "more oil is better" misconception.

To summarize, oil mixture is and has always been a compromise between adequate engine protection and efficient combustion and power.

A Quick Word About Two-Stroke (2T) Oil Types:

Not all 2T oils are created equal while we firmly stand by the adage that any oil is better than no oil in an emergency situation, it is best to avoid the low-priced, general-purpose (outboard motor/lawn equipment) two stroke oils generally found at gas stations and autoparts stores. For most scooter models, it is advisable to go with a name-brand motorcycle grade oil. Brand preference can be a tricky can of worms, but in the interest of clarity, most of our terminology below will relate to the Motul-brand products that we generally stock and use in the shop. Once you have established an oil type and formulation for your scooter, it is a good idea to stick with it and not to mix different oils together.

Two stroke oils come in several basic types. Among these are natural petroleum (mineral) oils, fully synthetic oils, various formulas of petroleum/synthetic blends, and vegetable-based oils (usually caster bean based). Very few modern 2T motorcycle oils are pure mineral oils, and there is really no advantage to using these. Mid-range synthetic/mineral blends like Motul 510 are acceptable (and arguably even overkill) for most vintage scooter applications, but a high quality, full-synthetic oil like Motul 710 will offer better protection for higher performance machines or those that are riden hard. But don't let yourself start to think that high numbers are always better; Motul 800 is truly designed for extremely high-revving racing motorcycles and is overkill for ANY street application, particularly any sub-225cc classic scooters. Also keep in mind that because of its high viscosity, Motul 800 should never be used with auto-lube oil injector systems. The final type, caster bean based oils like Castrol R, Blendzall or Maxima 927, do offer superb engine protection and have the bonus benefit of smelling like victory; if you grew up at race tracks or riding dirt bikes from the '60s through the '80s, this is the smell of being a kid. That said, castor bean oil is really not very well suited for road bikes. While it does a great job of protecting engine components at high revs, it is notorios for leaving excessive deposit buildup on the piston, ring grooves and combustion chamber and is best suited for engines that race once or twice between rebuilds. Also, like Motul 800 and other very high viscosity racing oils, caster oil should never be used with auto-lube devices.


Most classic European scooters consist primarily of a two-stroke engine mated to a manual transmission (gearbox) through the means of a manual "wet" clutch. These components nearly always feature "unit construction," meaning that the the engine and transmission components are housed in the same casting assembly, but separated by wall channels and seals.

Auto-Lube (Oil Injection Systems):

Throughout the years, two stroke oil injection systems have gotten a bit of a bad rap. A lot of this had to do with failures on a lot of poorly designed vacuum-driven systems on early Japanese bikes, but most of the undue criticism of the Auto-Lube systems offered on many later Vespa models is primarily due to "mechanics" of the '80s and '90s misunderstanding the system. We have rebuilt and investigated dozens of machines that had been laid up for years or even decades due to heat-seizures allegedly caused by Auto-Lube failure. In all of these cases, the culprit has always been some combination of incorrect parts installed by an amateur-level "mechanic." The complicated explanation in a lot of cases is that, while the US market got Auto-Lube as standard on all Largeframes from around 1968-on, it wasn't common in Europe until at least the mid-'80s. So generally, when aftermarket parts were mail-ordered from Europe, there was never any assumption that they would need to be Auto-Lube compliant. Something as simple as the wrong carburetor base-gasket would block the oil channel. Sadly, we still sometimes see this inattention to detail today, even with all of the information out there.

As mentioned above, oil mix ratios are always a compromise. Another great advantage of the  ingenious (Spica) Auto-Lube systems found on Vespa models is that they solve this compromise conundrum in a unique way by employing a dynamic-ratio metering device. At idle, when protective demands are minimal but risk of "loading-up" the spark plug and bogging out is higher, the "injector" mixes at around 0.5%. At full throttle, maximum protection kicks in and it mixes at close to 3%, a ratio which in any other rev range on the same engine would cause multiple negative side-effects. And of course, the system modulates dynamically at all points in between these extremes.

What About The Gearbox? (Trasmission Oils):

The gearbox (transmission) is lubricated separately from the engine section and is done by means of a different oil. The oil in the gearbox must be compatible with the natural cork plates that make up the wet clutch system. Also note that most modern oils, even those proclaiming to be gear oils, contain additives that are incompatible with not only the clutch plates, but also with several of the non-ferrous metals that are used in bushing and bearing surfaces within the transmission/clutch section of the case. Because of the increasing difficulty and confusion involved in finding oils with the correct properties in this day and age, we have sourced our own specially formulated vintage scooter gearbox oil which is now available through our store.

14819 Aetna Street

Van Nuys, CA 91411


(833) 55VESPA

Manual Oil Mixing By Model Type: