What I discovered after 100K miles: Is a used BMW 740i engine worth it? After clocking over 100,000 miles in my 2013 BMW 740i, I’ve learned a thing or two about used BMW 740i engines. Owning this car for six years has shown me that a second-hand BMW 740i engine can still perform brilliantly if it’s been looked after properly. Through chats on online forums, visits to dealerships for diagnostics, and advice from my trusted mechanic, it’s clear that not every used engine is a safe bet. Some have been thrashed, others ignored, and a few tinkered with beyond what BMW intended. My own engine, thankfully, is still going strong, but it wasn’t without its hiccups early on.