Do we go FURTHER or FARTHER?

English for Today by Ganiu Abisoye Bamgbose (Dr GAB)

Do we go FURTHER or FARTHER?

I think ~farther~ research is needed (nonstandard).
I think *further* research is needed (standard).
Both “further” and “farther” are the comparative forms of “far”, but “further” is preferred when we mean “more” as used above.

I think her house is ~further~ away than I thought (nonstandard).
I think her house is *farther* away than I thought (standard).
“Farther” is preferred when referring to distance although many native speakers also use “further” in this sense.

I want to ~farther~ my education (nonstandard).
I want to *further* my education (standard).
Another difference is that while “further” can serve as a verb to mean “to progress”, “farther” cannot perform this function.

In relation to “truth”, both “farther from the truth” and “further from the truth” have dictionary entries. While the former can be said to be preferred in American English, the latter is common in British English.
GAB