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Motormouth: Which oil to use for a moped?

Q: I recently was gifted a 1979 Negrini moped. It has a 49cc, two-cycle engine. After some extensive cleaning it appears to be in good condition. The owner’s manual calls for the gas oil mix to use 20 weight motor oil. (20 weight is also used in the transmission). I have not been able to locate a source for straight 20 weight motor oil. I have concern about using any other type or weight of oil in the gas mix, because of plug fouling or engine seize. Can you offer a suggestion for source of 20 weight or a comparison chart of current two-cycle oil equivalents?

— M.B., Easton, Pennsylvania

A: Just like the return of cicadas in the spring, bikes abound. I had to look up Negrini before I could attempt an answer. Since I still couldn’t, I turned to an expert chemist, Tom Wicks, who has created stuff and consulted for several well-known engine products companies. Tom states that two-cycle oil is fine for the engine and automatic transmission fluid would be best for the gearbox. The engine’s spark plugs, piston rings and exhaust ports may carbon up from 20 weight oil. Any two-stroke, air-cooled, chainsaw oil at a 20:1 ratio is fine. Ace hardware carries a synthetic two-stroke oil that keeps things clean. “The 1979 Negrini moped could probably easily run on old French fry vegetable oil,” joked Wicks.

Q. I have a 2017 VW Turbo Jetta. I always service the car at the dealer where I bought it. I am scheduled for my next service on May 15, 2021, when my estimated mileage will be 60,000. I am currently at just under 55,000 miles. Obviously, I won’t reach 60,000 miles unless I drive to New York and back twice from Florida. So, my question is, do I take it in based on the date or the mileage?

— B.G., Boca Raton, Florida

A: Oil change intervals are disappearing in favor of mileage intervals and service reminder lights. For most other motorized devices such as airplanes, maintenance is based on hours of operation, so a car’s mileage roughly correlates to time of operation. Many service facilities still give owners reminders based on time but check your manual’s maintenance schedule. The reminder on your instrument panel will tell you when it is time to do an oil change.

Q: Your recent article regarding a Ford Escape battery not staying charged, and being repeatedly replaced, may have to do with the battery sensor, located on the negative terminal. It tends to corrode and not allow the vehicle to properly charge, even if the battery is new. My son’s 2013 had the same problem. Ford diagnosed the sensor as bad, and the battery has been good since.

— K.D., Chicago

A: You reminded me of an important point. Many vehicles, not just Fords, have battery sensors to provide information to the body control module (BCM). The module uses the input for many systems as well as to determine the battery state of charge to activate the alternator and even to control the stop-start systems if the battery gets low. The systems even know when the battery is getting weak from age. Dirty and corroded terminals are the most common problems. Look for the connector at the negative battery terminal, but some makes put it on the positive post and others even use one on both terminals.

 

(Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest.) 

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