All,

I have a 2009 TL SH-AWD and it seems as of late this past week or so I have heard knocking upon acceleration when the car has sat for a bit. I use premium fuel (91 oct) and was wondering if this is something that others have heard of?

Chip

 

Mine sounds like a diesel engine when I first start in cold mornings. Goes away in about a minute. Been told its normal.

 

Reading through the various comments here and on reddit.com/r/cars and /r/autos, everyone says letting the car idle while cold isn't the most ideal thing you can do. They say drive it right off, but don't stress the engine too much (over 2-3kRPM) until it's fully warmed up. I dunno how true this is, but it seems to be the general populous consensus.

When I do that, there is a heavy sound coming from the engine, but it goes away after I get to about a tick mark or two into the temp meter (5 mins max, usually just a minute or two).

 

If it's below 40* F outside a vehicle should warm up at idle for a good 5 minutes, imo.
All the oil is down in the crank of the engine and is thick - and cold, somewhat like a thin molasses.
A warm up will heat up the oil for better lubrication - and easier on the engine.

 

Synthetic engine oil will not thicken at all, even under cold temperatures.

Especially with the 0W20 weight oil, which is the lowest possible viscosity oil when still cold.

 

Mine too, glad to hear it is normal.