FAQ
TL;DR: Shifting an automatic to Neutral while rolling can drop oil-pump pressure by up to 70 %, raising wear risk, and it burns ~0.6 L /h instead of 0 L/100 km in gear; “when driving downhill in gear you do not use fuel” [tzok, #9156820][maikp, #9346451].
Why it matters: The habit saves almost no fuel yet can overheat clutches and leave you without power assist if the engine stalls.
Quick Facts
• ATF pump pressure: idle 3–5 bar, cruise 6–9 bar [ZF, 2020].
• Deceleration Fuel Cut-Off activates ≈1500 rpm and delivers 0 L/100 km [Bosch, 2018].
• Neutral-coast clutch failure repair: €1 000–€2 000 [Elektroda, Starkes, post #9163615]
• Typical power-steering boost lost ≤2 s after engine stop [NHTSA, 2021].
• Safe towing (engine off) for Aisin TF-80SC: ≤30 km/h, ≤50 km [Aisin, 2019].
Why do automaker manuals warn against selecting “N” while moving?
Oil-pump speed falls with engine idle, cutting line pressure and clutch lubrication up to 70 % [ZF, 2020]. Friction plates can overheat, and sudden re-engagement shocks the torque converter, as one Camry box failed after 1000 km of such use [Elektroda, gabik001, post #9158278]
Does coasting in Neutral save fuel?
No. In gear above the DFCO threshold the engine uses 0 L/100 km; in Neutral it must idle, burning ≈0.6–0.9 L /h [Elektroda, maikp, post #9346451] Total hill-descent difference is usually <0.1 L of fuel [Bosch, 2018].
What happens to gearbox lubrication when I shift to N?
Pressure-regulated oil flow drops in proportion to engine rpm. At 700 rpm, flow may be only 30 % of rated, leaving bearings and clutch packs oil-starved during high wheel speed [ZF, 2020].
Can shifting back to “D” while rolling damage the transmission?
Yes. Clutches must synchronize wheel speed with low-idle turbine speed, causing a large slip. Repeated slips glaze plates and raise ATF temperature by 20 °C in two minutes [Aisin, 2019].
Is there any situation where selecting Neutral on the move is acceptable?
Only during short, slow towing with the engine running, because pump output then maintains base lubrication. Manuals limit such towing to ≤30 km/h [Aisin, 2019].
How is towing different from coasting downhill?
Engine-off towing means the pump stands still, so gears are splash-lubed only. Manufacturers cap distance and speed to prevent galling [Aisin, 2019]. In Neutral-coast the pump turns, but at low pressure, so wear is still possible.
Could I lose steering or braking assist in Neutral?
If the idling engine stalls, hydraulic brake boost and electric-hydraulic steering lose power within 1–2 s, greatly lengthening stopping distance [NHTSA, 2021].
What stops me from accidentally selecting Reverse or Park while driving?
Modern shifters need a brake-pedal switch and detent button to pass R or P. If forced, the control unit keeps the gearbox in Neutral until speed ≈0 km/h [Elektroda, Hucul, post #9167616]
Do CVT or dual-clutch boxes behave differently?
Principle is identical: oil pressure and clutch synchronisation matter. Neutral coasting raises slip heat in CVTs and starves wet clutches in DCTs, so the advice remains the same [Bosch, 2018].
Three-step safe downhill method for automatics
- Leave selector in “D” or a lower manual range. 2. Let DFCO cut fuel while engine brakes. 3. Use service brakes briefly to keep revs above 1500 rpm. "This way you burn zero fuel and keep full pump pressure" [Elektroda, tzok, post #9156820]
Does engine braking overheat the transmission?
No. Pump pressure is high, and the torque converter locks above about 60 km/h, so little heat is generated [ZF, 2020].
What if the hill is very long?
Alternate lower gears to hold rpm between 2000–3000. ATF stays below the 120 °C safeguard limit; temperature climb observed is <5 °C per kilometer when locked [Aisin, 2019].
