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TIL my mechanic's 'crazy' engine theory might be right, 180k miles later
Had a chat with an old diesel guy in Tucson who swore engines run better with a slight vacuum leak, said it's about pressure waves messing with fuel atomization. I laughed it off, but after testing it on my beater truck for 3 months, the idle smoothed out and I gained 2 mpg. He also claimed big oil buried this research in the 80s, which sounds nuts but the data is right there on my dash. Anyone else tried tuning for vacuum leaks, or is this just survivorship bias with old engines?
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grant4781mo ago
Buddy of mine tried this on his old F-150 after swearing his grandpa swore by it... he said the idle got weird and lumpy but the truck did pull a little harder going up hills. He never got the mpg gain though, his gauge was broke so he was just guessing. Probably works for some engines but I wouldn't risk a new truck on it, that's just asking for trouble down the road.
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