Temp Gauge reading

**sHoCkAbSoRbEr** · July 29th, 2003 09:06 PM

Just a silly question here... when you start the engine (most esp on mornings) with the temp gauge still on C, is it OK that you can start moving and revving up your car? As for the Starex kasi, it takes too long before the engine heats up...

Sorry for being inno...

Thanks na din guys...

**OTEP** · July 29th, 2003 09:41 PM

I wouldn't rev it hard. Primarily because the oil has not really circulated yet.

Just drive easy for the first few kms.

**yebo** · July 29th, 2003 11:01 PM

it's not that the oil has not yet circulated, it's because the engine is still cold.

let me explain...

when you start your engine the oil pump already begins to pump oil. the oil is still cold but it is already going to the engine parts that need the lubrication. since the oil is still cold the viscuosity is still high, so it flows out more slowly than if it is hot. but it is already doing it's job, lubricating the rubbing parts like piston rings and bearings.

the engine needs to warm up before you can rev it up. why? that is because the parts that have tight tolerances like bearings and piston rings are cold and have not yet reached their operating temperature. if you rev it then since the coefficient of expansion of the metals are not the same being made of different alloys and metals, then things might break. the piston rings may be tight on the cylinders (rings are either chrome or cast iron, cylinders may be aluminum or hardened steel) and operating at high rpm will subject these to excess stresses and break them. also the bearings are made of different metals than the crankshaft and cranksahft bore in the block. these might seize as the different parts have yet to reach the temperature at which the expansion and tolerances will be at maximum.

in fact, engines designed to rev up immediately after starting (like emergency generators, fire pump engines, etc.) have jacket water heaters that keep the engine temperature at constantly near the actual operating temperature. these heaters do not heat the oil (which is in the oil sump/oil pan so it is cold), only the jacket water. the water keeps the block and thus the pistons, cylinders and bearings at near the operating temperature at all times. thus the engine can immediately rev up to rated speed immediately after starting since the different parts are at designed temperature where the tolerances are maximum.

so it's not the oil, it's the engine temp that matters.

**Karding** · July 30th, 2003 12:36 AM

if you wanna start moving while the engine is still under normal operating temp, make sure you dont drive it hard and. Take is easy until after a minute or so.

if you know you are getting into the freeway/highway after 3 blocks from your garage, let it warm up for a minute. If you have to take the street before the freeway/highway, you can start moving and take it easy on revving up.

engine temp and oil temp, correlated on why you wouldnt wanna rev it hard at start up.