I bought a new washing machine and so far, it works brilliantly.

[Mori]

so far: until now
I bought a new washing machine and so far, it works brilliantly.

Cambridge Advanced Learner's Dictionary & Thesaurus

so far: until now; up to this point
Detectives are so far at a loss to explain the reason for his death.

Oxford Advanced Learner's Dictionary

It was certainly the best match of the football season so far.

Martin Hewings, Advanced Grammar in Use, p. 180

When used, "so far" specifically directs attention to the relationship between the present and something in the past, which is exactly why we use the present perfect tense. However, I'm still unsure why the simple present and past were used in the previous examples. Could you provide some more context or a specific instance to clarify their usage?

P.S. Regarding the last example, is it one of those cases where the simple past is used instead of the present perfect in American English?

 

[5jj]

When used, "so far" specifically directs attention to the relationship between the present and something in the past, which is exactly why we use the present perfect tense.

That would be a useful piece of advice for learners if we added normally before use. However, as you have noticed, native speakers can and do use other tenses.

 

[jutfrank]

P.S. Regarding the last example, is it one of those cases where the simple past is used instead of the present perfect in American English?

I very much doubt it, if it was written by Martin Hewings. In this context, so far means 'up to that point in time' rather than its more common sense of 'up to this point in time'. This usage is not especially unusual.

The usage of so far without the perfect aspect is quite common, especially with stative verbs.

Detectives are so far at a loss to explain the reason for his death.

The present simple presents a simple fact, focusing simply on the situation as it currently stands. The use of so far optimistically suggests the possibility (or hope) that the investigation will yield productive results in the near future.

 

[Mori]

The present simple presents a simple fact, focusing simply on the situation as it currently stands.

Can we say it's somehow similar to still in this particular case?

 

[jutfrank]

Can we say it's somehow similar to still in this particular case?

Not really, no. It doesn't have any of the negative emphasis that 'still' has. Given the sense of optimism that it carries, it would be better to think of it as more like 'yet', as in Detectives can't explain it yet.

 

[Mori]

Not really, no. It doesn't have any of the negative emphasis that 'still' has. Given the sense of optimism that it carries, it would be better to think of it as more like 'yet', as in Detectives can't explain it yet.

Great!
I'd forgotten all about yet: Similarly, we can use yet with the simple present tense.

• We don't know yet.
• I'm not ready yet.

 

[jutfrank]

Similarly, we can use yet with the simple present tense:

• We don't know yet.

Yes. That's like saying 'We don't know at this point in time but we will know in the near future, if all goes well'. It's more 'forward-looking' rather than backward-looking, which the perfect aspect is used for. Very similar to the detective example.

 

[Tarheel]

A common expression is "so far so good".

Mike: How are you doing?
Ron: So far so good.

Ron is hopeful, but he knows things could change.

 

[Mike MC]

Not really, no. It doesn't have any of the negative emphasis that 'still' has. Given the sense of optimism that it carries, it would be better to think of it as more like 'yet', as in Detectives can't explain it yet.

How about a positive sentence like the one in the question title?
I bought a new washing machine and so far, it works brilliantly.
Isn't it similar to still?

 

[emsr2d2]

A positive sentence would be "I bought a new washing machine and it works brilliantly". Adding "so far" suggests that you're envisaging its performance declining. That might be because you're a pessimist or because you've had a similar experience in the past.

 

[EngLearner]

Are the following versions acceptable:

1. I bought a new washing machine, and it's been working brilliantly since then.
2. I bought a new washing machine, and it has worked brilliantly since then.

 

[emsr2d2]

Are the following versions acceptable?

1. I bought a new washing machine, and it's been working brilliantly since then.
2. I bought a new washing machine, and it has worked brilliantly since then.

Please don't use red in your text. It gets confusing when we then use red in our edits.

Note that "since then" is redundant. It also suggests that it only started working brilliantly after you bought it. That's not natural.
#1 is OK.
#2 doesn't work once you've removed "since then".