Saturday, October 03, 2009 - 01:43 pm, by: Mike Bradberry(Halflife)
An interesting test you can do for yourself is to find a piece of long downhill run near home and to do the following. Enter the top of the hill when your engine is cold at a given speed (say 50kph) and allow the car to roll freely in say 'D' and note the speed at a point 1-200 metres down the road. Do the same test with your engine warm and you will see a significant difference in the speed. This gives you an idea of the drag of the oil at different temperatures, but you could also try the same test next time you change your oil and/or try a different kind.
Sunday, October 04, 2009 - 08:22 pm, by: Peter Nitschke(Pen)
Apart from wind speed/direction, assuming other traffic didn't interfere and the Vogons don't try to make an intergalactic highway across the hill, what other factors would be at play.
Sunday, October 04, 2009 - 09:24 pm, by: Andrew Duaso(Andrewd)
Brake drag weight tyre inflation temprature wheel alignment exact starting point and speed engine idle speed transmission fluid temp weed crack and whatever else. Fact is in an auto the engine speed won't be high enough to use as viable data to prove that cold engine oil has drag on the engine. I believe it's all due to the diff and trans oil temps. It more a measure of rolling resistance. You will find the same outcome if the engine is switched off and test performed in N both cold and once car has been driven once diff oil temps and grand temps are up it'd roll more freely. There are heaps more things to consider but my iPhone is going flat
Monday, October 05, 2009 - 12:46 pm, by: Mike Bradberry(Halflife)
Peter, there is a hill quite close to where I live and I have started at the top with the engine cold at 55kph and at the bottom of this hill with no acceleration it reaches 86kph. With the engine plus transmission obviously, warmed, it gets up to 91kph. So I feel the difference is substantial between cold and hot. If I was to take oil types and grades into account, I think there would also be a difference.
Monday, October 05, 2009 - 04:33 pm, by: Mike Beck(Gold_40gt)
I agree with Mike. I find that to be the case.
Personally, like to warm my car up for this reason, I HATE driving it slowly through my suburb when its cold, it feels very 'restricted' until all the key components are warm.
Monday, October 05, 2009 - 06:08 pm, by: Matchy Loi(Ftk148)
Same, I try to get my car warmed up but I can't always do that. If I got time, I'll drive around the block really slowly a few times i.e. 10-20km/ph, my logic is that all drive train components will get warmed up such as differential fluid, transmission oil and the final thing I think is more of a placebo thing, which is the suspension and tyres.