Originally Posted by
Manwell
........I used to warm up my car's engine before driving, thinking it was beneficial, before I was told that a BMW tech told my boss that full throttle could be used after start once oil pressure was available. That made me suspect much of what we think is best for engines is based on our emotions, but engines don't care about what we may think, they're mechanical machines subject to physics, not feelings.
As Pilot DAR says, the BMW tech was not the one paying for the engine rebuilds or replacements !
There is no need to fully warm a modern car engine
before driving it, but you should be gentle. So I drive, but I won't use large amounts of throttle while the engine is still warming up. So if I encounter a typical slow driver trundling along at 40mph on 60mph limit road, I will not overtake them if my engine is not fully warmed up.
Gunning a cold engine can increase wear, which while not immediately apparent will eventually reveal itself as reduced longevity:
I vividly remember seeing two aircraft ramp guys returning to the staff car-park after their shift one morning. They each got in their cars, and the millisecond their engines started, they roared away at full throttle. It was absolutely no surprise to me that both their engines sounded like buckets of bolts being shaken around !!
Bear in mind that oil pressure indicated on the gauge does
not mean that filtered fresh oil has arrived at working pressure in all parts of the engine.
Years ago; before starting a Rover V8 engine that I had extensively rebuilt, I had a tool made so I could prime the engine with oil using my electric drill before starting it for the first time*. I started pumping with the drill and waited to see how long it would take before I saw oil arrive at the top of the engine (with the rocker covers off). It took 20+ seconds before I saw oil. Of course the oil passages had been completely empty, but even so, that was quite a long time before pressurised oil arrived at the valve gear.
So, NO !, I would never use large throttle demands on a cold engine ! Treat it with kid gloves until you notice that the engine cooling thermostat has opened. (You can observe this on the water temperature gauge).
And aircraft engines are always fully and carefully warmed-up before demanding take-off power - with very good reason
*I had of course used special assembly lube on all the bearings and camshaft, which protects an engine during its first start, but I wanted belt
and braces.
.