Cold Idle Speed Question...

[TheSilkySmooth]

Originally Posted by Lafiro

And here I thought in the cold it was better to use a lower number: 5w20, instead of 5w30..... ????????????????????

This is a thermostat controlled, water cooled engine - you dont change the second viscosity # (oil grade or weight) for winter use unless its extremely severe - like sustained 10F below zero and a short tripper. The first number really means NOTHING** other than the lower the # the bettter the extreme cold flow properties. Motor oil is ALWAYS MUCH THICKER when cold than at 200F. It would be actually better to use a 10w-30 and have a block heater than go to a 5w or 0w. Remember the piston clearance is large when cold and the oil has to be of sufficient viscosity to prevent galling and slap during that critical 5 min warm up drive. It also has to be thin enough to pump and flow. A HD diesel oil like Rotella T 10w-30 has a -40C/F pour point and is easily good for cold starting at 10 above F. A truely remarkable dino oil that has almost universal application from Motorbike to diesel tractor to Yaris to 350HP 327 Chevy II to 3HP Briggs Lawnmower.


** 5W means Winter and may exhibit oil flow similar to how a SAE-5 grade oil would flow if chilled at ~ 0deg C. This will be much thicker than a hot SAE 30wt but substantially thinner than a chilled SAE 30wt. You could call a modern single grade SAE 20 oil a 10W-20 because it would most likely demonstrate 10W cold flow - or better, due to the improved oil refining process compared to that 15 years ago. And GASP! most ALL USA sold synthetics are just refined, conventional paraffin oil. Big oil loves taking your monies and stickin it to ya.