Any bad effects by turning a car's idle rpm too low?

Question

Not so low that the engine dies, but just above that.

Answer 1

you may lower the oil pressure and that is bad for the engine.

Answer 2

If I knew what your working on Year make model and engine size and how many miles. Most modern cars have electronically controlled idle speed. Manually adjusting the throttle stop won't work and that throws the throttle position and closed throttle switch out of adjustment. Modern cars computer control won't like the base idle different than the learned value so much so the car will throw a ISC code and engine light. STOP WHAT YOUR DOING AND BACK AWAY FROM THE x*x CAR. Until you know what your working on.

Answer 3

yes itll require more gas to accelerate.

Answer 4

if car in question is not computer controlled keep tabs on coolant temp and oil pressure

especially in traffic.

unless you do a whole lot of "city" driving mileage gains will probabley be insignificant.

and you may create an off idle flat spot that will annoy you.

leaving idle alone and using a thinner oil {5-20}

will save more fuel and wont create a driveability problem [doing this in a computer controlled car will lower the percentage of idle port opening a couple of points [in effect same speed on less air/fuel mix]

Answer 5

bad throttle responce off the line i would think mate :)

Answer 6

It's more a driveability thing than whether the engine is bothered. It's not under load but it will labour at a less than optimum tickover. You stand a higher probability of stalling when you pull away from lights or junctions.