An interesting and informative post,
The online 2018 Which? report says:
'Best Buy award removed. It's a very good car, but we found the Lexus IS emits so much CO (carbon monoxide) in our tests, that it would fail to meet any EU emissions limits set this century. As such, we cannot possibly recommend it.'
'Should I buy it? No, it's a very good car under some driving conditions, but the concerns around harmful emissions mean we can't possibly recommend it.'
Having read Thackeray's post above, I found the Emission Analytics report and contacted Which? for their comments.
They told me that - The engine test is the 300h F Sport Automatic, which we evaluated in 2013 soon after it came out, a Euro 5 engine. When we test the latest Euro 6 engine, we will update the review with what we find; hopefully the later engines will be cleaner.