Sonett community forum

Engine Oil & Transmission Fluid Change Schedule



How often do others change engine oil & filter ?

I drive car 300 miles per year, using 10/30 standard motor oil (non-synthetic)

How often do you change Trans Fluid ?

I have Redline Synthetic MT 90 75w90 in car, last changed March 2016.

Thanks, Mark


Transmission fluid effective for at least 30,000 miles, so at your rate you're good for many years, at least a decade!


As said above, transmission oil can go for quite some time without being changed. However, I don’t believe a single interval can be recommended based on the information you provide.

Are you talking about a Sonett? Has the gearbox been modified? Is the engine stock or modified? How do you drive (slow, fast, or race)? Where do you drive (do you have all four seasons in their full glory)? Is the gearbox original or has it been rebuilt? Do you have any complaints about the gearbox? Is the car stored in a climate controlled environment, in a barn, or outdoors? All of this and more will affect your gear oil change intervals.

Engine oil is different, but similar. All of the environmental and driving habit questions still apply, but there is a minimum change interval that doesn’t change unless the engine is never started.

Because engine oil picks up combustion contaminants any time it is running, and those contaminants are malignant forces on engine internals whether it runs or not, if the car is started even just once a year you have an interval of at least once per year. Personally, at just 300 miles per year I would change the oil at the end of the driving season (depending on the hemisphere and climate you live in) so that it is stored with clean fresh oil.


Thanks for the info.

Car is 1968 Sonett, I drive easy, no faster than 60 mph. I live in No. California, try to drive car every week or 2, weather permitting (NO driving in rain or wet roads). Car lives in a non-climate controlled garage.

Gear box is stock to my knowledge, do not know if it ever has been rebuilt. It operates fine, but does feel a bit sloppy. Not sure how "tight" it may been when new. Currently have Redline MT 90, changed March of 2016.

Engine is stock to my knowledge, a 1972 1700cc, replaced before I owned car. Have no history. I have been changing engine oil & filter once a year, so I will continue to do so.

Thanks, Mark